The world is full of beauty - the Grand Canyon, the Alps, the Great Wall, St. Peter's basilica. Not all beauty is found in such grand scale, however. The structure of the smallest feather, jewels, coins and crystalline structures are only a few of the many examples of beauty which can be found in very small scale.
Photography of small objects also has many utilitarian purposes. Fingerprints are a classic subject, but forensic photography extends much further than that. Failure analysis relies heavily on photography, and the ability to picture the tiniest fracture details is essential in this work. Philatelists want to be able to send pictures of their collections to colleagues. Makers of small objects want photographs to advertise their products.
Small subject doesn't necessarily mean large format, of course. Large format equipment provides much greater versatility, however. This is mostly due to long bellows extension, always desirable with small subjects. In addition, you have an enormous lens choice and many film possibilities. Sometimes a large format camera is used as an extra long extension bellows with a 35mm or medium format camera mounted on the back.
How small is small? There is no firm answer, but a range from perhaps six times, down to one twentieth, of the film format size, is the range in which special lenses and techniques are most used. For larger sizes, normal lenses will usually work fine, while for smaller subjects, the use of a photomicroscope will ordinarily provide better results. Sometimes, perhaps for depth of field reasons, obtaining the desired size by photographing in moderate magnification, followed by substantial enlargement, is the most appropriate strategy.
Deciding what focal length lens you need to make images as large, as or larger than, the subject is easy. You need an extension of two focal lengths to get a lifesize picture. After that, every increase of one focal length gives you one whole number of magnification. Example: A four inch lens at 12" extension (three focal lengths) magnifies by two. Estimating coverage is not difficult either. Regardless of the focal length itself, when used at a given extension, a lens will give the same coverage as a lens of the same type with a focal length equal to the extension. Example: You have a 150mm lens you know will cover 4" X 5". At 12" (305mm) extension, you can be sure that it will cover 8" X 10". Coverage is very rarely a problem when working close to the subject.
You can take a picture of a small object with any lens, but for really good results you need a lens made for an appropriate conjugate ratio. This is a fancy way of talking about the ratio between the subject and the image. Normal lenses are optimized for situations where the subject is much bigger than the image, while for small item work the subject may even be much smaller than the image. It should be noted that the ratio is reversible. A lens which is at its best at 6:1 subject/image works equally well at 1:6. It may need to be reverse mounted to work properly, though.
Lenses are either symmetrical, where the back cell is a mirror image of the front cell, near-symmetrical where the two cells are the same in basic layout but subtly differ in detail, or asymmetrical with cells that do not resemble each other at all. The last type is apt to be a Tessar, or a Tessar derivative. Obviously, nothing would be gained by reversing a symmetrical type, while an asymmetrical lens must be reversed to get acceptable results if used at a ratio opposite to that for which it was designed. A problem arises when we are unsure if the lens we have is a near-symmetrical, If we can't find out from the maker, all we can do is to try it out both ways.
Some lenses made for small object work are terribly expensive. The market for these is very small, hence the high prices. Few are available used, and the prices reflect this. Check out "Luminar" at the dealers or on eBay. Fortunately. there are several very acceptable alternatives. The lenses made by Tominon for the Polaroid MP-4 system are readily available used at very modest prices. As a great bonus, they all fit onto (not into, the whole lens assembly goes on the front) Copal Polaroid self-cocking shutters which are ideal for close work and are frequently included with the lens. Most of them have been used only in laboratory environments so it's easy to find one in mint condition. There are six focal lengths. The 135 and 105mm lenses are Tessar types intended for copying work. They are very similar to enlarging lenses which we will consider later. The 75mm lens is a reverse Tessar. It is, therefore, intended for making mages which are larger than the subject, probably optimized for considerable magnification. At 50mm, the next in the series is too short for anything but substantial magnification. To cover 4" X 5" film, it will need to be making images at least in the twice subject size area. With say, 16' extension, it would magnify by seven. It is symmetrical. The 35mm is again a reverse Tessar, although here there is also the opportunity of using the older Rodenstock Eurygon, which appears to be a symmetrical type. This lens was made for the Polaroid MP-3. It may appear with a Prontor shutter which is interchangeable with the Copal. The last of the series is the 17mm, another symmetrical type. This is the least often seen of the lot and the one drawing the highest prices when it does appear. It is also the hardest to use, but it does give the highest magnification for a given bellows draw.
As suggested above, enlarging lenses can be very useful in small object photography. A lens intended to enlarge 35mm negatives will (reversed if necessary) do a fine job in photographing a subject somewhere near 24 X 36mm size on 4" X 5" or 8" X 10" film. You would be using it as intended, only backwards. Enlarging lenses intended for larger formats will work similarly in larger scale. Using an enlarging lens often calls for some ingenuity in mounting it (probably in reverse) to a shutter. Some lens makers have provided reversing adapters. Check with your maker to determine current availability. Otherwise, a step-up ring, or rings, and a tube of epoxy may get you off to a start. Digital cameras have resulted in step-up rings once again being available in small sizes. Check out www.porters.com.
Bausch & Lomb made some "Micro Tessars" and "macro" lenses which typically sell for very much less than Luminars. The construction is reverse Tessar, so they need no reverse adapters. They come with adapters which screw right onto the front of a shutter, usually a No. 4 Alphax. They were made in 72, 48, 32, and 16mm focal lengths. The three smaller sizes have "RMS" or "society" mounting threads, which are those used for microscope objectives. These lenses were made for many years, so some are coated and some are not.
A process apochromat in a short focal length, 50 to 150mm, can be a real find. Several companies made them, but not in large numbers. Some of these are symmetrical types, the "Repro-Claron" for example, and are ideal for 1 to 1 copying. A 135mm needs only 270mm (10.6") bellows extension to copy life size. They are not limited to this application, of course. Most of these are "dialyte" types which are very tolerant of wide variation in conjugate ratios. Small apochromats are often found in shutters, but if not, they are among the rather few lenses which might be worthwhile having professionally mounted in (or on) a shutter. These are physically small and have narrow coverage, so can usually be front-mounted on a moderate size shutter. (See www.skgrimes.com.) Some asymmetrical apochromats are in reversible mounts. You take off a trim ring on the front, exposing threads identical to those on the back. These are not intended for 1 to 1 work, but work well for magnified photographs. As compared to enlarging lenses, the process lenses have quite small maximum apertures, usually somewhere between f8 and f10. This makes them a little harder to use. At higher magnifications, diffraction quickly becomes a limiting factor. The image damage from diffraction depends not on the nominal "f" stop, but the effective aperture which varies with magnification. For example, an f8 75mm lens at 24" extension is working at an effective aperture of f64.
If you are blessed with very deep pockets, or if you make your living photographing small items, there are several specialized lenses well worth consideration. (You might also be lucky on the used market.)
The Rodenstock Macro-Sironar-N would be a great choice for product photography of small subjects. The cells reverse in the shutter, so you can have optimum results with subjects in a range from one-third to three times the size of the image. The chief limitation is that the smallest focal length available is 210mm, so a very long bellows is needed for magnification. It also is found in the 300mm length.
Schneider's Macro-Symmar HM is intended for the same sort of work as the Sironar, but the focal lengths available are shorter (120 and 180mm). Its design is more elaborate, and Schneider suggests a slightly wider subject size range. Schneider provides for higher magnifications with their M-Componon line which comes in 28, 50 and 80mm focal lengths.
If you feel highly experimental, there are some unusual lenses out there which might or might not produce good results in photo work. These were made for use in microfilm readers, optical comparators, measuring microscopes, et cetera. Many are marked with the magnification ratio for which intended. These rarely have iris diaphragms, but this is not always a handicap. The good news is that they are usually very cheap. Aside from eBay, they are usually found at surplus sites such as www.surplusshed.com and www.candhsales.com. Some lenses intended for 35mm cameras work well on large format cameras when the subject is small enough. The older Micro-Nikkors have long been favored for this sort of use, and reverse adapters for them are available, but there are others worth trying and reverse adapters are also available for Minolta, Pentax and Canon lenses, some of them manual focus only. You don't want a telephoto or a wide-angle type, particularly a retrofocus wide-angle. Should a wide angle lens fit onto the thick body of an SLR, it is surely a retrofocus type. If the manufacturer provides a reverse adapter for that particular lens, that suggests that satisfactory results can be expected.
Cine camera lenses are a fine choice for making really big photographs of really small subjects. The "normal" lens for 16mm cameras is a 25mm. One of these, mounted in reverse, permits magnifications in the 20X range if you have a long enough bellows. The relatively large aperture of these lenses reduces the diffraction problem. The front of your lens will be awfully close to your subject, though, so unless you can illuminate through your subject, lighting becomes very difficult. A book on photomicrography, the older the better, will give you some useful hints about lighting. Older books, though, do not cover fiber-optic illumination, which is very helpful when working with tiny subjects.
There are two items required for fiber-optic illumination. The first is a lamp housing which contains a halogen lamp and usually a fan. The other item is a light pipe which plugs into the housing. If the two come from different makers, they probably will not fit together. Sometimes the light is divided into two pipes, and sometimes into a ring. Some pipes are very flexible, while others are enclosed in a cover which is fairly stiff, but can be bent to point the light wherever desired. The flexible variety needs to be held in place by a clamp on a jointed arm. Sometimes a reflector on the front of the pipe is needed to avoid having to bend the pipe too sharply. This can be just a bit of heavy duty aluminum foil. To hold anything on the front of the light pipe, a piece of rubber tube is helpful.
Some years ago, I encountered a learned scientific article which was illustrated using an interesting method of avoiding the difficulty of positioning lights when working with the front of the camera too close to the subject. A 7", f2.5 Aero Ektar was positioned rear down one focal length (infinity focus) away from the subject. A small lens was then used to magnify the aerial image from the Ektar. The illustrations in the article looked to be good quality. Another approach to reducing this problem is a cone shaped extension between the lensboard and a shutter mounted lens, or between a large shutter and a barrel mounted lens. Either of these can be very helpful when working at higher magnifications.
The focal length of normal lenses can be changed by the use of "close-up" or "diopter" auxiliary lenses. The quality of the resulting images depends on how well the main lens and the auxiliary get along with each other. If you have an auxiliary lens, try it, you may like it. In view of the very low cost of many available lenses known to produce good results though, I don't see much benefit in buying an auxiliary to try out.
Ring light units (flash, or otherwise) are often suggested for use in photographing small subjects. They can indeed be useful, but have limitations. When too close to the subject, they illuminate a ring around the subject, not the subject itself.. The lighting is very flat - good for some subjects, bad for others. A piece of foil blocking off part of the ring may be helpful.
Unless you are a real mathematical whiz (I'm a mathematical incompetent) you can use some help in calculating exposure when working within eight focal lengths of the subject. There are several calculating aids available, but the one I like is that found in old (mine is a 1965 edition) Kodak Master Photoguides.
Unfortunately, at very long exposure times you bump up against an additional problem called "reciprocity failure" This means that at extremely low (or high) levels of the light falling on the film, the film doesn't work at the expected ASA number. This varies from one film to another, so either advice from the manufacturer, or testing, is required to determine what results to expect. Color films may also require use of corrective filters.
When near 1:1 subject/image ratio, normal front focusing won't work. All that happens is that the image size changes. Back focusing works to a degree, but the real answer is to focus by moving either the whole camera or the subject. A gadget called a "laboratory jack" is a convenient way of moving the subject. It resembles an automotive scissor jack on a smaller scale, but with an enlarged platform. The new price is high, but they are available on eBay fairly often. They are very strong and can lift an elaborate lighting setup along with the subject. Linhof made a focusing rail to assist in this problem.
Although any large format bellows camera can be used for small subject work, some are much better than others. The two main desirable attributes are long draw and rigidity. At high magnifications, movements are rarely used and most specialized macro cameras don't provide them. Alignment is just as important as in enlarging, and is easier to ensure when base, column and camera are all one assembly. Many microscope makers, such as Nikon, Olympus, Zeiss and Leitz, have produced special-purpose equipment items along these lines. Aside from the Polaroid MP-4, they are apt to be expensive when found.
A few words about shutters. The Polaroid/Copal shutters mentioned earlier are excellent, but only for rather physically small lenses. For larger lenses, the bigger the shutter, the better. A large shutter means less chance of vignetting. You don't need high speeds, in fact you will often be making very long exposures unless using flash. The less I have to get my fingers into the area between the front of the camera and the subject, the happier I am, so a self-cocking type like an Alphax or an Ilex Universal is my choice. You might be able to find one of these with a bad lens in it. This would be good, because the bum lens has two threaded areas which you might be able to use in making adapters. Even if you intend to have a machinist make adapters for you, he will be glad to have the lens as a sample of what threads are needed. A cone shaped adapter would be more expensive, but very desirable. A few such shutters were made for projection applications and have no diaphragm, which eliminates one possible nuisance.
It is easy to shake the camera when making an exposure. Use a cable release, or better yet a rubber bulb. If a cable release, be sure that it is bent when you use it.
Over the years, there have been far too many macro lenses made than can be discussed here. Fortunately, there is an English language website which presents basic data on many of them. Dr. Klaus D. Schmitt is the editor. The site is http://www.macrolens.de. In addition to the basic data, there is a forum and a bibliography.