Macro photography. Getting to the limits of any system

Macro photography. Getting to the limits of any system

Written by Marina Parha and George J. Reclos Friday, 29 January 2010 00:00

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Article Index
Macro photography. Getting to the limits of any system
Page 2: Depth of Field
Page 3: Hints and Tips
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Macro photography is close-up photography. The accepted definition of macro is that the size of the image projected on the "film plane" (i.e. film or a digital sensor) is close to, or the same size as, the subject. On 35 mm film, for example, the lens is typically optimised to focus sharply on a small area approaching the size of the film frame. Most 35mm format macro lenses achieve at least 1:2; that is to say, the image on the film is half the size of the object being photographed. Many 35mm macro lenses are 1:1, which means the image on the film is the same size as the object being photographed. Another important distinction is that lenses designed for macro are usually at their sharpest at macro focus distances and are not quite as sharp at other focus distances. (1)

Any small subject, or part of a subject, can be macro photographed. Photographers shoot coins, stamps, toy setups etc. To us, macro photography means wild life: insects, spiders, worms and flowers. This presents some difficulties and requires careful planning and experience to ensure the final result is satisfactory.  Our subjects are often to be found on the ground - which in turn means that an acceptable angle for shooting them requires us to lay on the ground, often in mud or water. Maximum magnification means getting very close to creatures which, by nature, fly or run away if they can. Maximum resolution, detail and sharpness must be acquired at the same time as a considerable depth of field; this, in turn, means a very small aperture but this will allow diffraction to kick in, which reduces resolution and detail. The natural colours of a subject  should be preserved but when you work with such a small aperture at a close distance, light is never enough, so you must use a flash unit. This will result in the colours being "washed out". Raising the ISO settings is an alternative but this will adversely affect the detail and create more "noise".  Bokeh is also an issue; if the subject is to stand out the background should be as least distractive as possible. However this can be an issue given the size of the subject (the same depth of field required to get maximum detail on all the parts of the subject usually captures a lot of the background in detail too, given the small size of the subjects). In short, possible options and alternatives appear to have different downsides.

Macro photography has created a lot of controversy amongst photographers. Some regard it as an art  in itself while others think of it as mere “recording” what already exists, which allows limited, if any, opportunities to the photographer to show their creative side. Capturing an image on a recording medium is what photography is all about; this definition does not allow for the distinction of 'recording' and 'arty ' photos.  In our opinion a correctly framed and exposed subject in macro mode, shot from an appropriate angle, can result in an extremely pleasing photo -  not to mention that it is technically far more demanding than many other types of photography.

Getting close

Getting close to your subject refers to two things. Firstly, approaching the subject physically: as with all wild life there are techniques and strategies one can employ, particularly where moving subjects are concerned. Secondly, it refers to having the kind of equipment which will allow you to focus at a very close distance, thus yielding maximum magnification or, in digital terms, an image of a small subject formed by as many pixels as possible. Fortunately there are many ways to do that; this will be the subject of the presentation that follows.

Start by using a lens specifically designed for close work and with a long barrel for close focusing, called a macro lens. Some manufacturers call it a micro, which might actually be scientifically more accurate but can be confusing since it differs from the established jargon. A macro lens might be optimised to provide its best performance at a magnification of 1:1. Some macro lenses can achieve higher magnification – up to 5:1 macro - enabling photography of the structure of small insect eyes, snowflakes, and other minuscule but detailed objects. However, "standard" (1:1) macro lenses are more common. There are different categories of macro lenses, depending on their focal length:

• the 50–60mm range is typically used for product photography and small objects. This kind of lens usually focuses very close to the subject therefore the working distance is minimal. It can rarely be used in wildlife except to shoot flowers or other, not mobile, subjects.
• the 90–105mm range is the standard focal range used for insects, flowers, small objects. The subject to lens distance is about 10-15 cm which, although not big, is enough to light a subject and still leave it some breathing space.
• the 150–200mm range gives more working distance thus it is typically used for insects and other small animals. The subject to lens distance is between 20 and 40 cm which allows more insects to feel secure and not try to hide from the photographer. Using this range of lenses requires higher shutter speeds to avoid blurring due to hand shaking.
  
• some zoom lenses currently available provide a macro option, but they generally do not allow a 1:1 magnification. (1)
  

Another way to shoot at large magnification is to extend the distance between the lens and the film or sensor by inserting either extension tubes or a continuously adjustable bellows with no optical components between the camera body and the lens. The further the lens is from the film or sensor the closer the focusing distance, the greater the magnification and the darker the image for the same aperture one gets as a result. Tubes of various lengths can be stacked, decreasing lens-to-subject distance and increasing magnification. Bellows or tubes must be removed for normal working at longer distances. They can be used in conjunction with some other techniques (e.g. reversing the lens).

Placing an auxiliary close-up lens in front of the camera's taking lens. Inexpensive screw-in or slip-on attachments provide close focusing at very low cost. The quality is variable, with some two-element versions being excellent while many inexpensive single element lenses have obvious faults such as chromatic aberration and reduced sharpness of the image taken. This method works with cameras that have fixed lenses and is commonly used with bridge cameras. These lenses add diopters to the optical power of the lens, decreasing the minimum focusing distance and allowing the camera to get closer to the subject.

Attaching a telephoto extender between the camera body and the lens. A 1.4×, 1.7x or 2× teleconverter gives a larger image, adding macro capabilities. As with an extension tube, less light will reach the film or sensor and a longer exposure time will be needed. However, the working distance remains the same as without the teleconverter. In contrast to extension tubes, teleconverters add optical elements in the light path thus altering the image quality. The advantage is that you still work from the same distance.

Reversing the lens using a "reversing ring". This special adaptor attaches to the filter thread on the front of a lens and makes it possible to attach the lens in reverse. Excellent quality results up to 4 x life size magnification using fairly cheap, "standard" (not specially designed for macro) lenses can be produced. Special reversing rings are available for cameras with all-electronic communications between the lens and the camera body. These allow all camera functions, including open aperture metering, to be used. When used with extension tubes or bellows a relatively cheap but highly versatile macro system can be assembled.

Reversing a lens of smaller focal length in front of a normally mounted lens using an inexpensive macro coupler, which screws into the filter threads on the front of the two lenses to join them mechanically. This method allows most cameras to maintain the full function of electronic communication with the normally mounted lens for features such as open-aperture metering. The magnification ratio is calculated by dividing the focal length of the normally mounted lens by the focal length of the reversed lens (for example, when an 18 mm lens is reverse mounted on a 300 mm lens the magnification ratio is 16:1). The use of automatic focus is not advisable as the extra weight of the reverse-mounted lens could damage the autofocus mechanism. The working distance is significantly less than the original lens.

Another way of taking close up shots is to use your wide angle lens, provided it can focus really closely (those that do usually indicate that, for example, the Sigma 28mm f1.8 EX DG lens). Technically speaking these are not macro shots as they fall short of the 1:1 ratio. However you can still shoot 1:2 or 1:3 using a wide angle and in the process get some interesting angles, too.

Professional photographers or hobbyists who have been long in the hobby tend to be well equipped for macro photography, if this is an area of interest to them. Their kit usually contains extension tubes, bellows, focusing rack, macro lenses, ring flash etc. This has not always been the case. An article we read recently reminded us of an old trick used by people in the field when money was scarce and photographers had to work with what was available. The trick was to reverse the lens. At the time there was no adaptor to reverse the Nikkor on our D2X (and, naturally, there was no adaptor to reverse the Pentax 50 mm f/ lens on the Nikon). So what we did was to reverse the Pentax lens on the Nikkor lens. The Nikkor has a 52 mm filter thread and the Pentax a 49 mm one so this was not immediately possible. As far as we knew a male/male adaptor with a 49 mm thread on one side and a 52 mm on the other was not available - which was confirmed after making a couple of phone calls. We borrowed an idea from another photographer and used two step up rings a 49-55 and a 52-55 mm. The two rings were brought together and kept in place with an extremely strong cloth adhesive tape (the white collar you see in the picture below). We then glued them together by adding lots of silicon glue on the inside. The silicon glue hardened within minutes and ready we were. We tried it carefully on a table to make sure that the two rings would not fall apart and then decided it was time to take those close up shots of insects which were found dead in the summer and we collected to keep us busy during the cold winter months. All filters were removed from both lenses (they were put back in place once the session was over) and the aperture of the reversed lens was set to its maximum value (1.7). The "primary" lens was set to f/16 to have the maximum depth of field without the extreme loss of quality which occurs at f/22 although any aperture could have been used. After checking all the specimens we had we decided to work with the wings of a cicada which have a combination of transparency and lots of fine detail on them. Following that we also took some photos of a cicada exoskeleton found on a tree during the summer (actually we had four of them since they are too fragile to rely on them lasting long term). We noticed that photos taken using this way were somewhat sharper by comparison to similar photos taken using a bellows and had a better depth of field (although we do not quite know why). The downside is that focusing is really difficult; the way to do it is to move the camera back and forth till your subject comes in focus. Another disadvantage is that this system will only focus on one plane, which means that the lens to subject distance is fixed (about 50 mm). The advantage (apart from the quality of the image) is that you still have full i-TTL flash and all the automations of your camera (except focusing of course, which has to be done manually). In the second session we used the Novoflex focusing rail which made focusing a pleasure. This is a cheap solution (less than 10 Euro) providing 1:1 macro with full automation and i-TTL flash metering, which could be of special interest to those who own old normal lenses sitting somewhere in a closet, collecting dust. To avoid vignetting caused by the interior of the reversed lens it is preferable to use a lens with a larger thread than the primary one as a reversed lens. With the 12 Mpixel camera used, this is not a very serious issue because the final image can be large enough to be impressive but with lower resolution cameras this may be a problem. Some photos we got with this setup can be seen here  while photos of the setup itself can be seen at  Taking Fish Photos.

For those who may think this sounds way too complicated or specialised there is no need to worry. None of the above is necessary to get started. A prosumer camera can do the trick to begin with. Just put it on “macro” mode and may be put an inexpensive close up filter on it, if it accepts one. Those owning an SLR camera, digital or not, can get a set of extension tubes to get started. Photographers who get eventually hooked by this type of photography can build a system over the years.

Lighting in macro photography

There are various ways to light subjects in macro photography. Below is a presentation and discussion of these.

1. Natural sunlight. Many regard this as the best source of light for most types of macro work. Although it is preferable to work with a lot of light, sunlight does come with some drawbacks:

1. When the sun is high in the sky it creates some hard shadows and a very high contrast which may need to be “corrected” with fill in flash,
2. Its colour shifts during the day therefore an accurate reproduction of the colours on the wing of a butterfly or a flower, for instance, is not possible,
3. Sunlight hits the whole scene therefore even subjects located well behind your main subject may be visible in the final photo. In other words, the isolation of your main subject becomes more difficult,
4. The direction of the sunlight is fixed and there is nothing you can do about it. However, you may want to take the picture from a different angle which looks more interesting – sunlight alone may not allow for that,
5. With ISO 100 (for best image quality), f/8 (or f/5.6 at least) and a minimum shutter speed of 1/250 to allow for the lens to be handheld (assuming you use a macro with a focal length in the 150-200 mm range), you need a lot of natural light hitting the subject. Even then, you may wish to take the shot from the shadow side of the insect to show the detail of its wings or the hues created by the sunlight passing through the wings etc. In this case, you are always on the borderline. We tend to bellieve this is only possible in a sunny day – any light level below this requires use of a flash. On the other hand, nothing yields better and more natural looking results than natural light, if 'used' properly in the frame. You can create some really interesting pictures shooting backlit insects and flowers. You will be amazed how many parts of them are in effect semitransparent.

These photos are taken in natural daylight; the flash was not used. In the first photo the light hits the butterfly from the side revealing the texture on the body of the animal as well as the right wing. In the second photo we played with the sun and allowed it to back lit the butterfly thus revealing the transparency of the wings. A fill-in flash would bring more detail in the wing facing the camera but all the magic would be lost.

2. Flash. This is a portable source of excellent light quality, already balanced to daylight. Always the same colour, available at request, it can be directed where you want and can be regulated for intensity. When using a small depth of field  we need to add to the image as much light as possible and this is where the flash comes in. We can use the usual type of flash gun (the one that slots on top of the camera) or a ring flash (it attaches to the front of the lens and lights the subject all around). In addition, there are bars that enable photographers to use two flashes (one on each side of the camera). There are many advantages in using the flash in macro photography:

• the colour reproduction is excellent even though colours may come out a bit washed out if the flash light hits the subject directly,
• it allows the photographer to use a smaller aperture thus providing a greater depth of field,
  
• it results in sharper images as it highlights detail,
• it allows us to shoot subjects in the undergrowth and generally talking, in places where the camera cannot work due to the absence of natural light,
• we can use higher shutter speeds which, amongst others, remove motion blur (really a must considering what even a light breeze, let alone a flying insect, can do to a macro shot).

The small working distance means that even less powerful units are handy. Modern flash units allow for TTL metering and some offer a “balanced” setting which means blending the flash output with the natural light which falls on the subject. If used correctly, some excellent results can be obtained. A useful tip is to use the flash one stop lower than the natural light available; this way the flash output will be “hidden” in the photo. In general, flash light will reveal much more information on the subject because of its extremely short duration which “freezes” the subject. On the downside:

• flash units placed on top of the camera may drop the shadow of the lens on the subject. This is especially true if a long lens is used to work close to the subject,
• the flash light may frighten a subject which may change its position or just fly away,
• on-camera flash may produce reflections on the subject (this is particularly true of insects) which may be distracting or even ruin the photo altogether. In this respect off -camera flash units are much preferable. The use of a ring flash is also highly recommended for this purpose. It produces an even lighting of the subject though sometimes this results in a photo which is too “flat” and part of the texture is lost. Ring flash units usually have a low light output since they are meant to be used at a very close distance; they are specialised for macro work,
• in most cases it will ruin the bokeh of a photograph, allowing your medium to record detail in the background which is undesirable. This is a side-effect which can be only partially counteracted in a number of ways such as keeping the flash off the camera and placing it at the desirable distance from your subject, adjusting manually its intensity,  rotating it in a way which does not hit your subject directly etc, depending on the overall situation.

If the use of flash is desirable, or required, it is worth remembering that third party units are much cheaper than the ones made by the camera manufacturers. They may not communicate automatically with the camera, which means that manual adjustments need to be made prior to shooting each time; this requires an excellent knowledge of the flash unit and the ability to "read" the scene correctly. Useful as automation may be in some instances, we use manual settings quite often in the field. A useful reminder: flash units rely on batteries so it is advisable to carry a spare set of these with you when you are shooting outdoors. A battery pack with fresh batteries always comes in handy if you can spare the money. If you use rechargeable batteries make sure you charge them prior to your session and allow them to cool a bit before using them.

The photos below show a female scorpionfly; they were taken only seconds apart. The first one was shot with a flash in “balanced” mode and the second one using natural light. You can see the difference in the quality of light as well as the impact of the use of flash on the background.

Flash units (also called flash guns) have a guide number (GN). Although most units will automatically indicate which range they will cover for the aperture and ISO settings chosen, it is still imperative that the photographer knows the power of their flash unit and how to make some basic calculations while in the field. Some flash units can be used with high shutter speeds (higher than the synchronisation speed of the flash) by flashing repeatedly, which reduces the power output of the unit considerably. Although the calculations for this kind of flash use are possible, they are quite complex. It is preferable to rely on the indication shown on the flash unit. The table below indicates the maximum range for a flash unit with a guide number of 30 at different aperture and ISO settings; distances have been corrected for any ISO over 100.  A Guide Number of 30 at ISO 100 (in meters) means that the flash unit will be able to light correctly a subject with normal reflective properties and an 18% gray colour placed at a distance of 30 meters at ISO 100 and aperture 1. The guide number may be expressed in feet so the resulting range will be in feet, too. Some flash units can zoom to match the lens attached on the camera, which alters their GN considerably (it increases or decreases proportionally to focal length of the lens). We will disregard this for the time being. We will stick to the use of the GN with a normal lens – or else, a non-zooming flash head. The distance covered by the flash is expressed in meters.