Which Telephoto Lens and What for?

Which Telephoto Lens and What for?

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Article Index
Which Telephoto Lens and What for?
Page 2: Choosing a Lens (cont.)
Page 3: Using Teleconverters
Page 4: Notes and References
All Pages

Introduction

“In photography and cinematography a telephoto lens is a specific construction of a long focal length photographic lens in which the physical length of the lens is shorter than the focal length. In these lenses the optical centre lies outside of its physical construction, such that the entire lens assembly is between the optical centre and the focal plane. A regular lens of a focal length that is longer than what is considered a normal lens not necessarily a telephoto lens. A telephoto lens has to incorporate a special lens group known as a telephoto group [ … ]; nevertheless, non-telephoto lenses of long focal length are often informally referred to as telephoto lenses.”  (1)

A tele lens is used to magnify an object which is located far away from the camera. The degree of magnification depends both on the lens used and on the camera; in this presentation we will focus on DSLR cameras only.  To determine the degree of magnification of a given lens we need to divide the focal length of the particular lens by the focal length of the “normal” lens, which is supposed to cover exactly what we see. For example, suppose we use a camera with an APS-C sensor (smaller than 24 x 36 mm) for which the normal lens is the 35 mm. A 300 mm lens on this camera will magnify an object by 300: 35 = 8.5 times. The same 300 mm lens on a  full frame camera (sensor size: 24 x 36 mm) for which the normal lens is a  50mm lens will magnify the same object 300:50 = 6 times. Therefore if the subject is located at a distance of 30 meters, it will seem to you as if it is located at 3.5 meters if you are using an APS-C camera with a normal lens and at 5 meters if you are using a full frame camera.

The need for the magnification is obvious. A sparrow sitting on a tree 30 meters away is barely visible; the tele lens allows us to capture it, using the example above, as if it were standing 3.5 meters away.

Types of teles: Short – Medium – Long

Technically, telephoto lenses (teles for short) are classified as short, medium and long, depending on their focal length, which however is correlated to the size of sensor. Thus, anything from the normal focal length to double that is regarded as short, anything from double to quadruple is regarded as medium and anything over that as long. The table below shows this classification of focal lengths in correlation to the size of the sensor:

 

 

 APS-C

 (DX for Nikon) 

 Full Frame

 (FX for Nikon) 

 Short tele 

35-70mm

55-100mm

 Medium tele 

70-150mm

100-200mm

 Long tele 

180mm and over

300mm and over

 
 

Choosing a Tele Lens

Choosing a tele lens requires some thought, particularly as these “toys” can be quite expensive. Below we briefly present and discuss the most important things to consider.

1. The focal length of the lens

This depends mainly on two factors:

a. The size of the subjects we are trying to shoot and the relative distance we expect them to be from our camera.

Taking the subject – camera distance into account, the larger the subject we are trying to shoot the shorter the lens can be. Therefore, if we want to shoot eagles and we expect them to be at a distance of 10 meters, a 200 mm lens will do. However if we try to shoot a sparrow sitting at the same distance, a 1600 mm lens is required to get an image of comparable size (thankfully sparrows normally sit closer to cameras than eagles).

b. The particularities of our subjects and the shooting location.

Photographers need also to consider the subject(s) they are wishing to shoot. One of the main advantages of using telephoto lenses is that they allow you to shoot a subject from a distance. You may wish to do so either because it is impossible to approach any closer (e.g. due to obstacles on the way)) or in order to avoid disturbing or frightening the subject or being hurt yourselves (e.g. in the case of wildlife). In the two shots below you can see a photo being taken with a Nikkor 70-200mm f/2.8 VR attached on a Nikon D2x camera. The telephoto lens allowed the photographer to stay partly hidden in the tall grass and take some interesting photos of the bird’s nest where the mother was taking care of her chicks. Moving any closer in this case was difficult as the nest was located in the middle of a rather deep and muddy water stream. However, even if the nest was easily approachable the photographer would be ill advised to try and approach closer; the moorhen would immediately get alarmed and leave the nest, followed by her chicks.

 
   
 

In the next photo a Nikkor 80-400mm is set to its maximum focal length (400 mm) on a Nikon D2x camera. The photographer is hiding amongst tall reeds near the edge of the water at Sale Water Park (Manchester, UK). This made the human presence almost invisible to the grebes which went on with their courting ritual. 

 
      
 

Though long teles have considerable advantages in allowing us to shoot from a distance they do have their downsides, too. One of the main ones is the shutter speed required for shooting when using such lenses. The minimum shutter speed which should be used for any lens is 1/ focal length (so for a 200 mm lens the minimum speed is 1/200 seconds). Thus, a 200 mm lens should not be handheld if the shutter speed is not 1/200 or higher (1/300 etc). Keep in mind that APS-C sensors result in a cropping factor, essentially increasing the focal length of the lens by an equal amount. Thus a 300 mm lens on a Nikon D3, D700 or D3x becomes a 450 mm lens on a Nikon D300, D90, D2x etc. In the case of the APS-C sensors, the lowest speed you can hand hold your lens at becomes 1 / focal length x cropping factor in seconds (in the case of the 200mm indicated the speed then becomes 1/350 seconds). You should also keep in mind that this is the absolute minimum and requires really stable holding of the lens. Most of the times you will need to double the minimum shutter speed to be on the safe side.  (2)

The reason for this limitation is the blur caused by camera vibration. The severity of blur for a given vibration is proportional to the focal length of the lens. Lets say when we handhold a camera we get a tiny bit of motion at the front of our lens, maybe moving the camera 0.1 degree of arc during the time the shutter is exposing (this would be pretty good actually). If we have a 50mm lens mounted on a full frame camera, the field-of-view of our image is 39 degrees, so we would blur the image about 0.1 / 39 or .02% — a very small amount. If we blur the image the same amount (0.1 degree of arc) when using a 500mm lens, which has a field of view of 4 degrees, we would blur the image 2.5%. So for the same amount of motion while handholding, the 500mm image would appear to be blurred more than 10 times as much than an equivalent image taken with a 50mm lens. (3)

2. The maximum aperture of the lens

This can be of paramount importance when it comes to shooting with less than ideal lighting conditions, for example inside a forest, in the evening or simply during winter in an overcast day. As a general rule the less light available, the larger maximum aperture you want your lens to have.  Our Nikkor AF 80-400 mm f/ 4.5-5.6 D is a fantastic lens in full day light but mostly unusable during overcast winter days in the UK, as are most of our lenses with  a maximum aperture of f/4/5.

3. The speed of the lens

This is related to the point above.  A lens with a larger maximum aperture (e.g. f/2.8) is faster by comparison to a lens with a smaller maximum aperture (e.g. f/4)  because it allows you to get a higher shutter speed under the same light conditions. In practice this means that such a lens has two main advantages over slower lenses of equivalent focal length:

  • you will be able to hand hold it under lower light conditions and
  • you are more likely to be able to get the shutter speed required to stop the action of a flying bird instead of getting some blurred wings.

Speed is required when shooting fast moving subjects but a fast focusing lens is also a blessing when it comes to capturing an “unexpected” scene.

Unfortunately fast telephoto lenses are usually expensive and bulky. The fast long telephoto lenses are actually so expensive that are also called “exotic” lenses to signify that they are not an everyday convenience. What they give you in return is much faster focusing (an f/2.8 lens will always focus faster than a f/4 lens everything else being equal) and excellent image quality, if properly used, which is available even when the lens is used wide open.

Lens manufacturers usually offer a fast and a slower telephoto lens with the same focal length, so you always have a choice. As fast, we refer to 200mm f/2 – f/2.8, 300mm f/2.8, 400mm f/2.8, 500mm f/2.8-4, 600mm f/4 and 800mm f/5.6. If you can get one of these (with or without image stabilization / vibration reduction) you are getting the best glass available. Slower (and considerably cheaper) alternatives include the 180 f/3.5, 200mm f/4, 300mm f/4-5.6, 400 mm f/5.6 and 500mm f/5.6. In some cases, cheaper does not mean worse image quality – just a slower lens, slower in every aspect. Slower in focusing with a slower shutter speed under the same conditions. If the only thing you need a telephoto for is to shoot landscapes on a tripod, then there is no reason to go for a Nikkor 300mm f/2.8 lens, the Nikkor 300mm f/4 lens is equally sharp and costs one third of the price.

4.  Minimum focus distance

This indicates how close a subject can be to the nodal point of a lens before the lens can focus on it. (4) Most reputable lens manufacturers indicate the minimum focus distance of a lens in the manual but photographers can calculate this themselves by placing an object in front of the lens and measuring the minimum distance it should have from the front of the lens before the lens can focus on it.

Again, knowing what we will be trying to shoot and what distance we are likely to find it at from ourselves is a blessing. In the last photo above the photographer is using a Nikkor 80-400mm set to its maximum focal length (400 mm). The minimum focus distance of this lens is 1.5 meters. As anything which is nearer to the nodal point of the lens than 1.5 meters is practically invisible to the lens when the lens is wide open, the lens does not focus on the reeds close to it but on the main subject, which is the courting grebes about 10 meters away.

While, in this respect, photographers can count their blessings, the minimum focus distance can get in the way if the main subject comes too close to the lens: in this case the lens will simply be unable to focus on it.

5. Lens sharpness

The sharpness of a lens refers to its ability to render contrast, in other words its ability to shoot for maximum definition. There is a lot of discussion amongst photography enthusiasts (and professionals) about sharp(er) lenses; there is also a lot of information, including lab tests, regarding the relevant performance of tele lenses in simulated conditions. On the flip side of the coin it is occasionally suggested that all the talk about lens sharpness is gobbledygook when it comes to tele lenses: all modern teles are sharp provided one knows how to use them. (5) The proviso is most important: different lenses have different optics and will yield different results when used in the field. It is important to know the particulars (or limitations) of a lens prior to acquiring it to see how well these match the shooting conditions preferred or expected.

Indeed under the “right conditions” all lenses are sharp. Imagine shooting a still subject in perfect lighting; any two lenses will yield excellent results. The differences between two lenses start becoming obvious when conditions are not ideal. For instance, when light levels fall, the expensive lens will still be able to take fantastic shots while the cheaper one will start to reveal its weaknesses. It will hunt more, it will perhaps not be able to focus lock and finally the shutter speed may not be enough to “freeze” the subject. For moving subjects, especially birds in flight, focusing may be so slow that you will completely lose the shot, again and again. This is true for zoom lenses, too. The Nikkor 70-200mm f/2.8 VR II and the Nikkor 80-200mm f/2.8 will focus almost instantly, even if the phase contrast is minimal, even under low light conditions. In contrast, the Nikkor 80-400 f/4.5-5.6 VR and the 70-300mm f/4.5-5.6 VR II will focus fast under high light levels but as soon as the first clouds appear in the sky they will start hunting, sometimes indefinitely. This results in losing the shot.

6. Number and quality of lens elements

This is important to minimize optical aberrations.  “Aberrations are departures of the performance of an optical system from the predictions of paraxial optics. Aberration leads to blurring of the image produced by an image-forming optical system. It occurs when light from one point of an object after transmission through the system does not converge into (or does not diverge from) a single point. Instrument-makers need to correct optical systems to compensate for aberration.” (6)

Contemporary technology does not yet allow a lens free of all optical aberrations. Good quality lenses, however, balance these out. The quality of lens elements is usually indicated by a number of acronyms following the lens name, for example: ED (Extra dispersion glass), APO (Apochromatic), N (Nanocrystal coating) etc. (7)  Characteristics such as these indicate the ability of the lens to handle better (or correct) chromatic, spherical and / or other optical aberrations such as lens flare, vignetting etc. 

The construction of the lens does not just aim to reduce optical aberrations.  It also determines the way in which the out-of-focus area of the photo is captured. This, in photography, is referred to as bokeh.  The importance of the out-of-focus areas is obvious: a busy or poorly captured background attracts the eye and therefore detracts it from the main subject in addition to being aesthetically unpleasant.  Good quality lenses have built-in controls to manage the way in which the out-of-focus areas are rendered. These lenses are indicated as having good or excellent bokeh.

 

 


7. Lens type and Lens - Sensor combination

Lenses are designed for use on film and / or digital cameras. Further, some lenses work best on DX formats while others work on both DX and FX formats. Make sure to chose a type which is designed for your camera and has the correct mount for it, too.

Though some tele lenses work on both DX and FX formats the results we get when using them with different sensors are different. So far there is nothing new. One would expect the better quality sensor to produce the best results. Well, it is not as easy as that.

The level of resolution and detail you get in an image is proportional to the number of pixels used to create it. It follows that the capacity of the sensor of the camera to record detail affects the quality of the photos taken with long lenses. The question is, is it preferable to attach our longest telephoto lens on a 24.4 Mpixel full frame camera or an APS-C sized 12.4 Mpixel one? It is generally believed that, unless the full frame camera has a lot more Mpixels, the APS-C sized one should be preferred. We have tried our telephoto lenses on a Nikon D3X and a Nikon D2X.

The D3X offers 24.4 Mpixels on a sensor measuring 24x36 mm, thus those millions of pixels are spread over a surface of 864 mm2 and the pixel density is 28.240 pixels / mm2.  On the other hand, the D2x has 12.4 Mipxels spread over a surface of 370 mm2, therefore the overall pixel density is 33.513 pixels / mm2.

It is clear that the D2x offers a greater pixel density (1,18 times more pixels for the same surface). Thus, other things equal (no diffraction, very low ISO settings) the D2x offers a more detailed image for the same image surface. It would take a 29 Mpixel full frame sensor to match this.

That is not the end of it. If you attach the same lens on both cameras, it is evident that the image produced by the D2x is larger than the image of the D3x. Since with DSLRs “what you see is what you get” it is evident that the same bird, sitting at the same distance, will be larger in the frame of an APS-C sensor, i.e. it will occupy a bigger surface on it. How much larger? One and a half times in each direction (horizontally and vertically) or a total of 2.25 time larger in terms of surface.

If we now calculate the greater pixel density for the D2x sensor, we have 2.65 times more diodes recording the image than what we get in the D3X. Therefore, when you view your image on your screen, you will have 2.65 times more pixels forming the subject than you would if you used the D3x instead (with the same lens attached on both cameras).

 
    
 

We tried to analyze the two pictures of the heron (above) taken at the same time using the D2x which had the Nikkor 80-400mm f/4.5-5.6 VR fully extended at 400 mm (which is effectively an 600 mm lens) and the D3x with the 300 mm f/2.8 lens mounted on it, coupled to an 1.7x TC, which is effectively an 510 mm lens. What we have to compare now is the differences between these two combinations. Since we refer to 600 mm for the D2x, the difference in sensor size have been accounted for, therefore the two cameras are now regarded as full frame cameras. Thus, the D3x has a 24.4 Mpixel full frame sensor and the D2x a 29 Mpixel full frame sensor.

What the two sensors see is schematically presented in the diagram. The blue rectangle stands for the 600 mm lens and the red rectangle stands for the 510 mm lens. It is evident that the D2x will record the subject better (assuming it fits in the blue rectangle) since it will record less empty space (gray area in the diagram)). How much less space?

 
 
 

To identify this we need to look at the ratio between those two areas at any distance from the camera. We have a horizontal axis, in which the 510 mm will cover x510mm and the 600 mm will cover x600mm. Consequently, in the y axis, the 510 mm will cover y510mm and the 600 mm will cover y600mm. When we multiply x510mm x y510mm we will get the area covered by the 510 mm lens and the same will be true for the 600mm lens when we multiply x600mm x y600mm.

In order to make some calculations using basic trigonometry we need to get some right triangles, which are easily found if we take half from each dimension for every lens. Starting with the 600mm lens, x600mm/2 is one side of the right triangle in the horizontal axis, d is the distance from the camera and b is half the angle of view for the 600 mm lens on the horizontal axis. The distance does not matter since it is the same for both cameras. The angle of view for the 600 mm lens is 3.44o horizontally and 2.29o vertically. We will use half that values to calculate the x600mm/2, based on the right triangle which is formed there. For the 600 mm lens the horizontal dimension of the recorded area is x600mm. x600mm/2 = d x tan(b) and finally  x600mm/2=0.0300286*d. Therefore the horizontal dimension of the recorded area is two times that or: x600mm = 0.0600573*d. Similarly, working for the vertical axis, the vertical dimension of the recorded area for the 600 mm lens is y600mm=0.03997336*d. Thus, the overall surface recorded by the 600 mm lens is 0.002400692*d2.

Moving on to the 510 mm lens, the angle of view for it is 4.0o horizontally and 2.7o vertically. The horizontal dimension of the recorded area is x510mm. x510mm/2 = d*tan(a) and  x510mm/2=0.034920769*d. Therefore the horizontal dimension of the recorded area is two times that or: x510mm=0.06984153*d. Similarly, working for the vertical axis, the vertical dimension of the recorded area for the 510 mm lens is y510mm=0.04713261*d. Thus, the overall surface recorded by the 510 mm lens is 0.0032918137*d2.

A direct comparison between the two surfaces shows that the 510 mm lens will have to “cover” 1.37 times more surface than the 600 mm lens for an image standing at the same distance from the lens (any distance from the camera, this ratio is constant). Therefore the sensor of the camera with the 510 mm lens can spare 1.37 times less diodes to record the same object, since it needs to cover more surface. In reality, this means that the sensor of the camera with the 510 mm lens can devote only 100 diodes to record a subject when the same sensor with the 600mm lens will devote 137 diodes for the same subject sitting at the same distance from the camera.

Time for some (easy) multiplications: With the 510 mm lens you will get 1 Mpixel devoted to your image when you will get 1.37 Mpixels for the same image using the 600 mm lens. Going further down the road, you will get 3 Mpixels devoted to your beloved subject with the 510 mm lens and 4.1 Mpixels with the 600 mm lens. The difference starts to show.

Just to make it more interesting: If you have a 10 Mpixel sensor, which you can fill completely with your subject (all 10 Mpixels of it) using your 600 mm lens, you will only “use” 7.3 Mpixels of that sensor for the same subject if you use a 510 mm lens.Thus, a mere 90mm difference at the long end of your telephoto lens allows you to save almost 30% of your pixels. Not a bad deal after all.

It all started as a joke, while discussing the difference in image quality between the D3x and the D2x shooting the same subject at the same time. The results were quite better with the D2x which didn’t seem to make much sense (even though a TC was attached on the D3x). When 100% crops of the two photos were compared side by side, it became evident that the D3x lacked detail which the D2x didn’t.

This analysis provided an explanation for this finding. Simply put, the D3x recorded the image using much less pixels than the D2x because of the two factors we analyzed in this section. It has a lower pixel density (1.18 times less) and a lens with a shorter focal length (resulting in 1.37 times less pixels). Overall, the difference is 1.6x in favour of the D2x. For every Mpixel the D3x used to record the image, the D2x used 1.6 Mpixels.

We concluded that it is better to use your long telephoto lens on a camera with a cropped sensor and a high pixel density. To put it simple, all 12 Mpixel DX Nikon cameras (D2x, D300, D90, D5000) outperform the Nikon flagship by a good margin.

8.  Lens weight, construction and design 

This appears to be easier than it is in reality. A good quality, weather protected, sturdy lens is bound to perform better in the field and last longer than a flimsy plastic counterpart. Yet such a lens is a burden to carry, particularly if a photographer enjoys walking around to find appropriate subjects. More often than not the size and weight of a lens determine its usability. Again, it all depends on the type of photography you enjoy, the length of your photo sessions and the conditions you are likely to find yourselves under while shooting. Remember that the important thing is to take good photos, not expensive or exotic gear. The right balance is different for each person depending, amongst others, on physical built, condition, shooting habits, preferred subjects etc. Make sure that your lens will give you good photos rather than shaky hands and a back ache from carrying it.

The design of the lens is equally important. Check that all the controls are easily accessible and that switches between different modes of operation can be made quickly and effortlessly (fiddling with the lens in the field can be very frustrating and the cause many a lost shot). It is not the lens that will take the photos, you will. The lens is just a tool you will have to use correctly to capture what you want. To achieve this you must be comfortable using it and familiar with it.  Ideally camera and lens combination should be an extension of your own body.

Top of the line telephoto lenses, both zoom and primes, are really heavy lenses. The lighter of them will easily surpass the 1.5 Kg mark (which becomes 2.5 Kg with the camera, straps etc.), while the really big teles start at 3.5 kg (see table below, in the Price section). These lenses, in order not destroy the camera mount, must be properly supported – and that adds to the price as well as the flexibility of the photographer.  In order to reduce the weight of the lens some manufacturers have used magnesium alloy for the construction of the body of the lens (the Canon EF 800mm f/5.6 L IS USM is one of these lenses). This results in a relatively lighter lens but a much higher price.

 
    
 

Flexibility is not the name of the game with exotic teles and the more exotic the lens the less flexible it becomes. They are difficult to carry around, they need a special technique to be used correctly, they must be mounted on a tripod or other kind of support; they are not the kind of lens you just drop in your bag and off you go. They are meant for those who need them and know exactly what to do with them.

9. Focusing characteristics

By focusing characteristics we refer collectively to the way in which a lens focuses. Some lenses can focus only manually, others have an autofocus function (usually indicated as AF on the lens). Other characteristics include IF (internal focusing), S = silent (usually indicated as AF – S). Manual focusing is required on certain occasions however a fast autofocus lens is preferable particularly when shooting without the aid of a tripod or other support as both hands are required to keep your camera and lens steady. We find that Internal focusing is better for shooting wildlife; the movement of the barrel of the lens is bound to frighten and drive away your subject, particularly at close distances. For the same reason silent lenses are way preferable to their noisier counterparts.

10. Vibration Reduction (VR)

Also referred to as Image Stabilization (IS) by Canon, vibration reduction  (Nikon) refers to a number of techniques used by camera and lens manufacturers to counteract camera shake while shooting and therefore allow photographers to get sharper images. (8)

VR comes in handy in a number of cases, particularly with long focal lengths (tele lenses):

  • Minimizes or counteracts the movement of the photographer’s body, including shaking hands (all the more so when carrying heavy tele lenses),
  • Allows you to stop down a variable amount of stops (usually 2-4) depending on the vibration reduction system of the lens (for Nikon lenses VR allows you to stop down 2 stops while the company claims that VRII allows you to stop down four stops); (9) this is particularly useful when you need depth of field in relatively low light conditions or
  • Allows you to use your lens in light conditions in which it otherwise would be unusable, i.e. use lower shutter speeds, which is particularly useful with long teles, (10)
  • Allows you to take better photos of moving subjects by panning.

11. Resolution

This refers to the amount and quality of information which a lens is capable of recording. To identify it lenses are formally tested; test results are available on the internet.

It is beyond the scope of this article to discuss or even present such tests; it is of little use to duplicate information already available. The point to remember is this: it is important to make sure that the resolution of the sensor of your camera is similar to this of your lens. If you get a lens which has less resolution than your camera you downgrade your camera (essentially not exploiting its full potential); the photos will only have as much information (quantity and quality – wise) as the lens can capture. If, on the other hand, the resolution of your lens far exceeds this of the sensor of your camera you are most probably throwing good money down the drain; the sensor of your camera will only record at its maximum capacity, ignoring the remaining information which the lens captures. You may be well advised to invest on higher quality lenses, however, if you plan to upgrade your camera.

It should be noted that differences of the type discussed here will, more often than not, not be visible in small resolution prints. However the differences become obvious when cropping or larger prints are required.

12.  Price

Cameras come and go but good lenses stay. In fact, the arsenal of good lenses is what binds a great many photographers to a specific brand name.

A good lens will offer you very high image quality, very high resolution, little or no vignetting, minimal color aberration and flare and no ghost images. A reasonable photography enthusiast will more likely want to be ready for all eventualities. In practice this means a long, fast tele with nano crystal coating, extra low dispersion glass and VRII.  And the price of it is? Get ready for it:

 
Lens Weight Price Lens Weight Price
 
200mm f/2G ED-IF AF-S VR NIKKOR
2900g
€3735
£3065

Canon EF 200mm f/2L IS USM

2520g
€5471
£3700
 
300mm f/2.8 ED-IF AF-S VR NIKKOR
2850g
€4325
£4499

Canon EF 400mm f/5.6L USM

1250g
€1231
£890
 
AF-S 400mm f/2.8G ED VR NIKKOR
4620g
€7932
£6669

Canon EF 600mm f/4 L IS USM Lens

5360g
€7923
£6,072
 
Af-S II 400mm F2.8 If-Ed NIKKOR
4400g
€7051
£5301

Canon EF 800mm f/5.6 L IS USM Lens

4500g
€11215
£9,110
 
500mm f/4D ED-IF AF-S II NIKKOR
3800g
€6712
£8000

Canon EF 1200mm f/5.6L USM

16,500g
€100000
£91917 
 
600mm f/4D ED-IF AF-S II NIKKOR
5900g
€8021
£8179 

Sigma 300-800mm f/5.6 APO EX DG HSM Lens

5880g
€8017
£5970
 
Nikon 200-400 mm f/4G ED-IF AF-S VR Zoom-N
3600g
€6082
£4,949

Sigma 200-500mm f/2.8 EX DG APO IF

15700g
€20500
£17,823
(11)
 

Do you get the drift? These toys are not cheap. Neither are their peripherals, should you ever need to replace them (the hood for the Nikkor 300mm f/2.8 currently costs £260). As most of us have to scrape and save to invest on our hobbies serious thought is required to determine what exactly it is we need and what we can do without. While a lens with nano-crystal coating, extra low dispersion glass, 17 elements and VRII is a great piece of kit, if the price of it is out of reach you will never benefit from it. The VR system alone can add up to £800 on the price of a lens; maybe a lens without it (or generally, with lower specs) is enough for your needs – and well within your budget.

Start by being reasonable: you do not need a 600mm lens to shoot sparrows. It makes more sense to look for a friendlier bird which will come closer to you or improve your technique for approaching your subjects. Long lenses may give you that extra magnification but how do you plan to use it? How often do you go on photographic safaris or trips? Are you prepared to spend a photo session using one lens only or do you prefer the flexibility different lenses (and subjects) offer? How familiar are you with using teles?

Talk to people who have used or are using long teles to find out their limitations. This is easy enough to do even if you do not personally know such a person: register in a reputable photography forum. Consider what impact these limitations will have on you and your photography. While additional focal length comes in handy on certain occasions it is totally useless on others. For example, when you need to approach close to your subject anyway because of barriers in the way (reeds, trees, rocks etc) or when the weather conditions interfere with the shot (haze, heat rising from the earth, wind etc.  The longer the lens the more likely it is that its performance will be affected by these conditions.).

Read reviews; there are plenty available on the internet, some of them by seasoned professionals. If at all possible, try renting or borrowing the lens you intend to buy for the weekend; nothing can tell you more than the actual use of the lens in situ.  (We have checked the price of renting the Canon EF 1200mm f/5.6L USM for a week in the UK out of curiosity: it was around the £2800 mark. One could buy an excellent lens for this amount of cash.)

A word of warning: there are considerably cheaper lenses available for the same focal lengths by third party lens manufacturers. The only thing these lenses have in common with the lenses of leading lens manufacturers is, in fact, the focal length. The differences in terms of construction and the technology used are massive and that is reflected in the price differences – as well as the performance of the lens. When budgeting for a lens remember that you get what you pay for. (12)

Zoom or fixed focal length lens?

There are those who swear by either type of lens and this is true among the authors, too. Most of the pros and cons of each type have been discussed in full length elsewhere. In this article you can also see the image you get using lenses of different focal lengths so you get the impression of the magnification – all shots were taken from the same spot. (13)

To us, the main advantage of top of the line zoom lenses is that they replace a couple of primes thus reducing the weight of gear to be carried around and that they offer flexibility in the composition in situ. The primes offer a bit of extra image quality and are usually a bit faster.

 
   
 

Zoom lenses come in a great variety and are consequently classified as “all around”, “good” and “top of the line”. In general, all around zoom lenses have a focusing range of 6x or more (like the Nikkor 18-200 mm VR lens) and offer a mixed bag as far as the optical quality is concerned. Some focal lengths / aperture combinations work pretty well some may produce mediocre results. Usually they suffer from distortion which may be of a different type at various focal lengths. This is even more so for zoom lenses which cover the wide angle – telephoto range. Lately zoom lenses with a 15x range (Tamron 18-270 mm) have appeared in the market and, although they seem to sell well, the image quality they deliver is, as expected, average. In fact all around zoom lenses are a compromise between convenience, price and image quality. In some cases, when working under perfect conditions (lots of light and the lens used at its optimal aperture and focal length) you may come up with a really nice photo. However, this will be the exception rather than the rule and you can’t expect low budget gear to give you results comparable to lenses which cost 4 or 10 times more.

Good lenses usually offer a 4-5 x zoom range like the Nikkor 70-300 mm VR or the Nikkor 80-400 mm VR lenses. These are usually slower than the top of the line zoom lenses both in focusing as well as the maximum aperture they have (usually f/4.5-5.6). However, under the right light conditions, excellent results can be obtained, which is very rarely the case with the “all around” zoom lenses. Optically they are closer to the top of the line zoom lenses but suffer from their small maximum aperture which, apart from slower shutter speeds results in slower focusing and a lot of hunting. They are very hard to be used to track birds in flight – especially in a cloudy day. However, once they lock on, they can produce comparable results. 

However, this may not always be the case. In the following photo, a “good” zoom lens simply fails to nail the hawk sitting on the electricity pylon, despite the high contrast between the bird and the bright sky.

 
 
 

Finally, there are the top of the line zoom lenses which offer a 2-3x zoom range and are extremely fast. In this category fall the Nikkor 70-200mm  f/2.8 VR, the 80-200mm  f/2.8, the 200-400 mm f/4 and the two monsters made by Sigma namely the 300-800 mm f/5.6 and 200-500mm f/2.8 – the latter requires a minivan to carry it to the shooting location. It should be noted that, although we refer to Nikkor lenses, most SLR camera manufacturers (Canon, Pentax, Olympus, and a limited range by Sony) offer comparable lenses both in quality and money. Independent lens manufacturers offer some great lenses, too, which will save you some money. We have not tried either of the Sigma monsters yet, but we are sure they are very well built and offer excellent image quality.

 


Using Teleconverters

It is a practical joke between bird photo shooters that, regardless of the focal length of your lens, there are still some mm missing at the long end. Wild animals try to keep their distance from all intruders in their natural habitats, especially the ones holding huge black or white telephotos. At some point we all found out the hard way that our pride and glory of a lens was simply not long enough. One solution is to get a longer tele but this, as indicated, may not be a good option for a variety of reasons. A considerably cheaper alternative is to get a teleconverter. No matter which telephoto lens you have, sometimes using a teleconverter is the only way to capture a specific scene adequately.

A teleconverter (or doubler) is a secondary lens which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens (the telephoto lens). For example, a 2× teleconverter enlarges the central 12×18 mm part of an image to the size of 24×36 mm in the standard 35 mm film format. Teleconverters are typically made in 1.4×, 1.7×, 2× and 3× models. (14)

The use of a 2× teleconverter results in doubling the focal length of a lens. A side effect of this is that the intensity of the light reaching the film or the sensor of the camera is decreased by a factor of 4 (the equivalent of doubling the focal ratio) while the resolution is also decreased by a factor of 2.

Teleconverters work similarly to a telephoto group of a proper telephoto lens. A teleconverter consists of a group of lenses which together act as a single diverging lens. The location of a teleconverter is such that the image produced by the objective is located behind the teleconverter at a distance smaller than its focal length. This image is a virtual object of the teleconverter which is then focused further away and thus enlarged. For example when a single negative lens is placed so that the image formed by the objective is located in the midpoint between the lens and its focal point the lens produces the image in its focal point enlarging it two times thus acting as a 2× teleconverter.

When used with somewhat slow lenses teleconverters may reduce the effective aperture to such a degree that the camera's autofocus system will no longer work; depending on the camera system, this may range from f/5.6 to f/8. The camera autofocus system usually delivers good results with lenses up to f/5.6. At maximum apertures smaller than that (f/8 or smaller) the amount of light entering the camera is too little for the autofocus system to detect phase contrast quickly and work.

Dedicated teleconverters only work with a limited number of lenses, usually telephoto lenses made by the same manufacturer. Using a teleconverter with an existing high quality lens is less expensive than acquiring a separate, longer telephoto lens. On the downside, as the teleconverter essentially magnifies the existing image circle as captured by the lens, it also magnifies any aberrations.

The teleconverters produced nowadays can communicate seamlessly with the lens and camera, particularly when they are made by the same manufacturer.  Older models sometimes prevent the camera’s auto exposure and auto-focus modes from operating. It is also important to remember that

  • not all teleconverters work well with all lenses,
  • teleconverters are most useful on fast lenses, or when taking photos in bright light,
  • they generally work better on fixed focal length lenses than zoom lenses and
  • using them with some lenses (such as the Nikkor 80-400mm f/4.5-5.6 VR or the Nikkor 18-200mm f/3.5-5.6 VR) is not recommended

Teleconverters offer a cheap alternative to really long focal length lenses which usually cost a fortune. They are small so they can fit in your pocket, they are light so you do not have to worry about the overall weight of your gear increasing by much. However, they are a sort of “emergency” lenses, in the sense that they are meant to allow you to shoot something which your “real” lens cannot reach – although at an expense. You have to keep in mind that they are essentially a second set of glass elements slotted between - and interfering with - your expensive prime telephoto and the sensor. This means that the resulting image will always be inferior to the one produced by the prime lens alone. The larger the magnification of the teleconverter lens the more the image quality gets downgraded.

It is worth noting that the higher the quality of your lens the less noticeable the adverse effects of using a TC will be in the final product (photo). The so called ‘exotic’ lenses usually outperform the sensor of the camera in terms of resolution. Accordingly the difference in the optical quality (due to the decrease of resolution by the factor of the TC) of the photo will be minimal, if at all noticeable, if a combination of a good quality prime with a good quality 1.4x TCs is used for a shot. When an 1.7x TC is used the image quality gets affected but a top quality prime (or zoom) lens will still give very good – or even excellent -results. With a 2.0x TC things get noticeable worse. Most photographers try to stay within the 1.4-1.7x range to ensure that the image quality is still very high. We have not met anybody using a 3x TC to get their views on the subject but we feel this should only be done if you desperately need the photo even if the image quality is poor.

We need to re-iterate that in photography the final result (i.e. the quality of the photo) is affected by a combination of factors rather than  simply the quality of a lens or a camera. Depending on the quality of the sensor and the way this compares with the resolving power of the lens mounted on the camera the use of a TC will affect the final product (photo) differently. 

In some cases TCs are really the only option available. As indicated, one such case is when the subject is so far away that your longest lens cannot deliver an image of an acceptable size. Another case is when there are more chances of taking a good quality photo using a lighter combination (camera+TC+shorter tele) than a heavier combination (camera+longer tele), particularly when appropriate support is not available.

When using TCs it is important to remember to adjust the exposure of the camera to compensate for the change of the focal length of the lens. Sure enough, the meter of the camera will recognize that the light hitting the sensor has diminished. This, however, is not enough.  As indicated, the minimum shutter speed for handholding a lens is 1/focal length in mm. When a 1.7 TC is attached to a 300 mm lens the lens effectively becomes a 510mm one. Thus, the previously sufficient 1/300 speed is now insufficient; a speed of 1/600 is the minimum required to handhold the lens. Opening the lens up may be an alternative but this is not usually sufficient because the maximum aperture has also been affected by the use of the TC (assuming you have a really fast tele, with a maximum aperture of f/2.8, the use of a 1.7TC will make this f/4.8 (1.7x2.8)). In practical terms, the attachment of the 1.7 TC is equivalent to stopping your lens down by 2.5 f/stops. This makes a massive difference while shooting. Though it is relatively common to be able to get an exposure of 1/300 at f/2.8 even at basic ISO you will need really bright light to get 1/600 at f/4.8.  The solution is to raise your ISO settings sufficiently to get the speed required. While doing this make sure you do not push your camera out of the acceptable ISO limits for it.

Techniques - Strategies

As one would expect, these differ depending on the tele lens in use. A 200 mm weighing 800grams is pretty different to a 600mm weighing 5500grams. There are certain things which are considered vital, however, when using tele lenses. It is up to individual photographers to consider the extent to which these are applicable in their case.

The main issue when using long teles is how to get sharp photos. There are three kinds of movement affecting a photo. The first originates from the camera. The second originates from the photographer (e.g. the trembling hands or simply your heart beat. Finally, the third kind of movement originates from the subject.

1.    Minimizing camera shake

So we found our subject, composed the photo and we are ready to shoot using a 400mm lens. Just as we press the release button the mirror moves up prior to the shutter curtain opening. The vibration caused by this mechanical move is accentuated by our long tele and the result is a photo lacking in sharpness. Using the mirror lock-up feature of the camera can result in improved sharpness. Different ways of using this feature are described by E. J. Peiker in his article “Advanced Long Lens Technique. Defeating the "Camera Shake" Enemy”. (15) 

If you are using support, use your body to stabilize your system - this is a tried and tested technique. Rest your free hand on your lens to keep it steady and push your head against the back of your camera (thus ‘jamming’ it between the lens and your face).  As with all techniques, practice makes perfect.

Using a rubber eye cap is recommended by a number of professionals; this acts as a shock absorber to minimize movements from the photographer’s head.

If at all possible, use the delayed release (timer) function of your camera with or without a remote control. This is only possible when your subject is static or very slowly moving – and again it requires the camera – lens combination to be mounted on a support system (preferably a tripod).

Finally, improve your shutter release technique. This is particularly important if the delayed release is not used. The recommended technique is to roll your finger unto the shutter release button instead of pushing down on it.  (16)

2.    Support

This becomes a critical issue with long teles. Even with good light levels, which means high shutter speeds allowing for a good number of lenses to be hand held, this is rarely feasible. The lens is heavy, the camera – lens combination is front loaded and needs steadying so that your hands will start shaking in less than a minute. Even the best image stabilization / vibration reduction system available cannot cope with hands that tremble.

The solution is to support the lens. This can be done using a tripod, monopod, beanbag or – for lack of the appropriate equipment – any steady surface that can be found around (we have often used a stone, rock or a thick branch of a tree. Even leaning against the trunk of a tree may help on certain occasions).

2a.  Tripods

Tripods are an extremely steady way of supporting your camera – lens combination. When using them make sure that the legs are properly extended and that all the knobs are fully tightened. If you need to leave some slack to ensure flexibility in following a moving subject make sure that the slack does not adversely affect the stability of your system. Professionals recommend trying to pull down on the tripod with your hand to make sure it is securely in place. Only then the lens – camera should be attached on it.

When selecting a tripod make sure it is sturdy enough to carry the weight of your camera + lens combination. Reputable manufacturers state the maximum load a tripod can take – take away 15% of that figure to be on the safe side or consider it as the absolute maximum and go for a bit extra. Alternatively you risk your expensive equipment which may gravitate towards the earth as the tripod loses balance or collapses under the combined weight.

Similarly, when selecting a tripod head, make sure it is easy to handle, sturdy enough to hold your lens without slippage and flexible. This is imperative to ensure effortless composition and accurate execution of the shot.

Adding some weight on the tripod itself greatly increases its stability. Do not extend the legs and the center column unless necessary. The shorter the legs the greater the stability. If you have a choice between hard and soft (but steady) ground, use the soft one, since it will act as a dampener and decrease camera shake.

Set up your tripod in a protected space, if at all possible; use a tree, shelter or even your body to shield your camera and lens from the wind.

Do not leave things dangling from your camera; straps and cables can cause vibration particularly during a windy day.

The advantage of using a tripod can be summed up in two words: sharper images. Depending on the weight and focal length of your tele a tripod may be a must. (17) The downsides of it are equally obvious:

  • Less flexibility in the field,
  • Carrying more weight (a sturdy tripod will add at least 4-5 kilograms to your field kit),
  • Added expense (carbon fiber tripods, which are lighter to carry, together with the appropriate ball heads and peripherals such as plates, grips etc will set you back at least the price of a good lens – think three digit numbers here).

If you plan to set up at a preferred location and wait for a subject to come in range, a good tripod is the ideal solution especially if the subject stays still or moves slowly. On the other hand, if you plan to walk around looking for a subject the combined weight of the tripod and the rest of your equipment will soon exhaust you.

2b.  Monopods

Monopods are a less expensive and more flexible alternative to tripods. However they do not offer anywhere near the support and stability a tripod does – and this can be a serious drawback with long heavy lenses particularly for amateur photographers.

2c.  Beanbags

Beanbags are used over other surfaces (or on the ground) to form a cushion over which the lens and camera are rested. Draped over a car window they form a platform which supports the lens when shooting from inside the car.  Over the years we have spent thousands of hours foraging areas looking for wildlife. We noticed that birds in particular are not afraid of moving cars but will fly away the minute the car stops and surely when a door is opened. We usually work as a pair - one drives very slowly while the other places the camera with the telephoto lens through the window opening (the beanbag comes in very handy to drape over the door part and stabilize the lens) and shoots. (18)

Used like this the beanbags are a good option, much safer and less threatening to wildlife than other methods such as setting a tripod in the car or shooting through the sunroof. (19)

2d.   Window and door mounts

Window and door mounts are also available; these accept a standard tripod head on which to secure your equipment. The issue with these mounts is that you have to drive with them in place or you need time to set up when you see the subject. This is usually a bad idea – by the time you are ready there is no subject to shoot. Driving with them in place is fine during the warm months but try it in cold or wet weather and you will soon start getting second thoughts.

If you are to invest either on a beanbag or on a mount bear in mind that the former is a much more flexible and easy to use tool in a variety of situations.

3.    Movement originating from the subject

The third kind of movement which can affect a photo originates from the subject. There is only one way to counteract this effectively and this is high shutter speed. High shutter speed is considered generally a must when using teles – the longer the tele the more it is required.  Note that even when you use high shutter speeds the use of a tripod may result in a better image.

You can achieve fast shutter speeds by opening your lens up (this is where fast teles come in handy) or increasing the ISO setting of your camera. Other things to consider are:

  • removing any filters that decrease the shutter speed (such as polarizers etc) unless you definitely need them
  • removing teleconverters if the light conditions are not favourable.

Lack of appropriate support in the field may result in limiting the use of a long tele in certain instances. Remember that the point is not to use a particular lens but to take a particular photo. In the following photo, the photographer had to walk inside a lake to shoot a pair of courting grebes. The bottom of the lake was a deep bed of mud, and therefore particularly unstable. Using support was not an option; the camera had to be handheld and she could only rely on the VR for image stabilization. Accordingly, though longer lenses were available, the lens of choice was the Nikkor 70-200mm f/2.8 VR.

4.   Other accessories

Long lenses can be used in a variety of situations: sports and wildlife photography are popular options amongst amateurs and professionals alike. If you plan to use your long lens outdoors you should consider the particularities of your shooting location and get prepared accordingly. Failing to do so may result in big disappointment as you may risk damage to your lens or not being able to use it in its full capacity.

A rain or splash protector is a must if you are shooting outdoors. Big teles in particular are bulky so your photography bag will most likely not be able to accommodate them if the weather gets suddenly wet. There are lots of different types available offering varying amount of resistance to water and dust. Get one that suits your needs and always carry it with you (it will not be much use tidily packed away at home while you are out in a T-shirt caught in a sudden summer shower with your new 300mm f/2.8). Rain protectors are also great by the beach to protect your camera and lens from sand or waves splashes.

You may need to shoot with the rain protector on so chose a type that allows easy access to the controls of the camera and lens while fully protecting both. Finally, choose an appropriate colour: a bright yellow rain protector may just defeat the point if you are trying to keep a low profile under the bushes in order to shoot that water fowl in the nearby stream.

Shooting wildlife may soon become a passion, in which case you may end up knee deep in a stream or lagoon with a considerably muddy bottom. A lot of photos taken at Strophylia Reserve, especially those showing eggs in birds’ nests, were taken with the photographer in the water till his waist. Wellies and waterproof overalls become a necessity; without them we would be simply unable to use the teles with any chance of getting some interesting photos.

If you are out shooting on your own and you enjoy the ‘active’ type of photography (i.e. moving around looking for a subject) you may want to consider a waterproof bag to carry your field kit.  Marshes are great places for wildlife but the ground is unpredictable and often gets flooded; protecting your expensive equipment from damage is of paramount importance. Consider that long teles are bulky and heavy so you cannot maneuver them as easily as shorter lenses; they are better off safely out of the way while you are exploring the ground or stumbling towards a good spot. There are various types of waterproof bags – including floating ones – available in the market. Choose one suitable for your needs but make sure it offers 100% protection for your equipment. Try it at home with something inexpensive but of equal weight to what you want to carry prior to taking it out to the field with you. If a bag is no good be inventive: we have often thought of inflatable kid floats ourselves!

Conclusions

Long lenses (teles) are attractive to a number of photographers; they are a must for certain types of photography. However they are neither cheap nor particularly versatile so they do require thought and planning prior to acquisition – and a lot of practice afterwards.

When choosing a lens try not to be impulsive. Get something which you will use and enjoy time and time again  – and most importantly – something that will allow you to be in control of the photos you take rather than something that will limit your ability to take photos by its many requirements.

Table of abbreviations for Nikon (Nikkor) lenses

This is presented in the images below:

 
      
 

Note: The numbers in parentheses in the table of abbreviations above correspond to the same numbers in the notes below.

 

 


Notes and References

1.   Wikipedia
2.   Marina Parha and George J. Reclos, When EV sounds like ET
3.   How to get Sharp Telephoto Images
4.   “A compound lens (a lens made of multiple glass elements, like basically any camera lens) has two nodal points. The front nodal point is the point in the optical system in which all the rays of light which enter the lens converge. The rear nodal point is the point in the optical system from which all the rays of light leaving the lens seem to radiate. That is, it’s the point on the optical axis from which the emergent ray leaves. The focal length of the lens is measured from the rear nodal point.” Quoted from Photonotes.org
5.   See for instance Ken Rockwell, Lens Sharpness
6.   Definition Wikipedia. See also Cambridge in Colour, Lens Elements and Image Quality. Moving the cursor under the image of the eagle on the right hand side shows various types of optical aberrations. A good article explaining lens optics can also be found in Wikipedia; vignetting (light fall off) is discussed at Toothwalker.org
7.   For example, see the presentation of the Tamron lenses at Tamron.com
8.   In this presentation we discuss only on lens VR systems, not camera image stabilization. It is worth bearing in mind that overall, lens VR systems are considered preferable to their equivalent camera systems. A good article on VR systems with photo illustrations is available at Ken Rockwell’s website.
9.   ‘Stop down’ refers to closing the aperture of a lens thus limiting the amount of light that reaches the camera sensor. If your camera is on f/4 and you go to f/5.6 you are stopping down by one stop. The opposite (going from f/5.6 to f/4) is called ‘opening up’.
10.   For example, imagine that the maximum aperture of your lens is f/2.8 (at f/2.8 your lens is wide open). To shoot a particular scene you need, at f/2.8, a speed of 1/250 at ISO 100. This would require roughly a level of lighting equivalent to 11 EV. You have a 200 mm lens mounted on the camera which, as a rule of thumb, requires at least a speed of 1/200 to be able to produce sharp images when handheld. The table below shows the speed required to shoot the same scene with reduced light (i.e. indoors, in an overcast day, during the evening etc):

 
Aperture

 f/2.8 

  f/2.8

 f/2.8

  f/2.8

 f/2.8

 
 Focal length

 200mm

 200mm

 200mm

 200mm

 200mm

 
ISO

 100

 100

 100

 100

 100

 
 Shutter Speed

 1/250

 1/125

 1/60

 1/30

 1/15

 
 Light  available (EV) 

 11

 10

 9

 8

 7

 
 Vibration  Reduction  required

 No VR, VRI or VRII

 VRI or VRII

 VRI or VRII

 VRII only

 VRII only

It is clear that depending on whether there is a VR system available or not and which VR system it is, the use of a lens is extended. A lens without VR will only operate in situations which fall within the first column – or better (i.e. with improved lighting) while a lens with the VRII will enable you to shoot sharp photos in considerably lower lighting conditions.
11.   Specifications from Nikon Europe and dcviews.com  referenced to Canon Europe. The price value is indicative; we looked at the internet, mainly but not exclusively at Amazon  and these prices are cited as current in September 2009. Prices will vary (in some products we found differences up to £2000) but bear in mind we are citing the cheapest prices found for each product.  Prices in € (Euro) were acquired mainly from Adorama, a couple of lenses from other sources.
12.   George J. Reclos and Frank Panis, Depth of Field and Prime vs Zoom Lenses
13.   This is not to say that third party lens manufacturers only produce inferior lenses or that leading brand lenses are always the best in their category. In fact some of the best lenses are currently available only by them (see the price table above). However, when they come up with a really good lens, the price gap between these lenses and the ones offered by camera manufacturers gets smaller. In most cases, you should expect to get such a lens at 2/3rd the price of the “branded” one.
14.   Wikipedia
15.   E. J. Peiker, "Advanced Long Lens Technique. Defeating the "Camera Shake" Enemy", Nature Photographers
16.   See M. Peterson, Proper Handholding Technique.
17.   E. J. Peiker (ibid) considers a 300 f/2.8 the limit; anything over that he recommends using on a tripod. We would re-iterate that the limit is a personal one and depends on the built and physical condition of the photographer.
18.   During the breeding season this is a must, since the person driving has to be very careful not to drive over a nest. In summer 2009 we used an SUV to explore a dried lagoon with five cameras and four persons in the same car. All four windows were down and cameras were resting on the door frames. In this case we had the advantage that it did not matter which side of the car the bird was since there was always a camera pointing at it.
19.   E. J. Peiker (ibid)
20.   Nikon Links
21.   By Thom.  We highly recommend you read the whole of this article to get the history of Nikon developments as well as compatibility information.
22.   Hardware Zone. You will find here an explanation of the abbreviations used by Canon.
23.   Wikipedia.  A very useful article with a list of Nikon lenses and specifications. See also Ken Rockwell, Nikon Lens Technology.
24.   Wikipedia
25.   Wikipedia
26.   DPReview

Further reading available at:

SLR Gear
By Thom
Ken Rockwell
Dpreview
Nature Photographers

 

Photos by the authors.

 

Acknowledgements: The authors wish to thank Frank Panis for his useful comments on an earlier version of this article.