ORTOGRAFIA 1. Vocals

Two of the most misused words in photog-raphy are probably "macro" and "micro."

Macrophotography is the art of making large photographs. Photomacrography is the art of photographing small subjects.

Microphotography is the production of very small photographs (e.g., microdots), and photomicroscopy is the photography of objects through the microscope. The term photomicrography is interchangeable with photomicroscopy. In addition, the term Close-up photographygenerally refers to

Macrophotography is the art of making large photographs.

Photomacrography is the art of photographing small subjects.

Microphotography is the production of very small photographs (e.g., microdots), andphotomicroscopy is the photography of objects through the microscope.

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work done between the shortest distance a normal lens will focus and lile size.

This chapter explores the two differ-ent ways that you can get closer to a sub-ject to obtain a larger image: photomicroscopy and photomacrography. In the former, a camera is attached to a micro-scope. The microscope's optics are used to gather the light for the image. In the latter, any one of a number of lenses and accessories, excluding microscopes, are used to obtain the needed image size.

The difference between the two is defined both by range of possible magnification and by the method of obtaining that magnification (Kodak, 1969). In photomicroscopy, the camera is attached to

and uses the microscope optics. Most microscope and camera manufacturers supply adapters that attach your camera to the microscope. Magnification ranges from about 2:1 to 50:1 or more.

Generally, the lighting used in photomicroscopy is limited due to shorter working distances, the nature of the microscope, and the high magnifications.

Magnification is calculated by dividing the size of the image by the size of the subject, and can be expressed as a deci mal (.5x is one-half lile size) or a ratio (1/2 size or 1:2). A magnification of 5 times would be 5:1.

In photomacrography, you can choose from a number of lenses, acces-sories, and techniques to achieve the needed magnification. Magnification ranges from 1:1 to about 50:1 and usable light sources are less restricted than in photomicroscopy.

One major difference, obviously, is that of magnification capabilities.

Microscopes have a definite advantage in that arca, but you pay a price for it. As the magnification increases, the depth-of-field decreases. Depth-of-field is the dis-tance in front of and beyond the point at which the lens is focused that the subject appears to be in focus (Behnke, 1991).

When photographing a mountain scene, the depth-of-field is nearly infinite, but at high magnification it may be a fraction of a millimeter.

Although photomacrography does not provide very high magnification, its advantage is greater depth-of-field. This capability is possible because photographic lenses contain an iris diaphragm to control the amount of light passed on to the film. As the lens is "stopped down,"

and the diaphragm opening becomes s maller, the depth-of-field increases.

Because of this feature, photomacrogra-phy is the preferred method for obtaining magnifications. Some microscopes have iris diaphragms, but they are expensive and hard to obtain.

PHOTO MACROGRAPHIC I EQUIPMENT

MACRO LENSES

Magnification of a subject is increased by extending the lens from the camera. A normal lens typically will take you no closer than 18 inches with a magnifica-tion of 1:5. A macro lens is designed to extend further and attain a 1:2 or 1:1 magnification. The optics in such a lens

Figure 12-1 Supplementary close-up lenses (Courtesy of Photomark)

are also designed for such close-up work.

Because of the decreased depth-of-field with magnification, you are essentially doing flat-field photography. Normal lenses are not designed for that job, but macro lenses are. Macro lenses are gener-ally available in two focal lengths: 50 mm and 100 mm. A 50-mm lens will attain a given magnification with less extension and light loss. The 100-mm lens gives you more working room and better perspec-tive. Macro lenses are also capable of smaller apertures, thus providing greater depth-of-field. A minimum aperture of f22 is standard for macro lenses, while f16 is standard for a normal lens.

Some camera manufacturers supply lenses that go beyond ordinary macro lenses in their ability to deal with higher magnifications and shallower depth-of-field. Such lenses include Zeiss Micro Tessars, Canon Macrophoto lenses, Olympus Zuiko Macros (in focal lengths of 20 mm, 80 mm, and 135 mm), and the

Leica Photar series ranging from 12.5 mm to 120 mm. Focusing must be done by moving the whole camera assembly and/or the specimen because these lens-es are nonfocusing. Such lenslens-es are supe-rior for the high-magnification work nec-essary in micromount photography. A 20-mm macro, for instance, easily obtains a magnification of 14 times on a bellows.

Dan Behnke, well-known micromineral photographer (Plate 21), uses the Olympus Zuiko macro lenses for his work.

CLOSE-UP LENSES

Macro lenses are not inexpensive, but there are alternatives that vary greatly in the quality of image attainable.

Supplementary close-up lenses are one of the options (Fig. 12-1). They work essen-tially like a magnifying glass and screw onto the front of your normal lens like a filter does. Their magnification strength is rated in diopters: + 1 diopters, +2 103

Figure 12-2 Extension tubes for Glose-up photography.

diopters, and so on. They can be pur-chased individually or in sets of three to four, and can be used individually or in combination to attain different magnifi-cations. Generally, the best magnification you can attain using diopters is 4:1. Aside from their limited magnification, their use degrades image quality by the addi-tion of too much glass in front of your lens.

Yoshida Industry Co. Ltd., of Japan, has recently introduced a product that is a great improvement on the old Glose-up lens systems. Their Raynox Model CM-3500 MicroExplorer is a series of three Glose-up lens assemblies that thread into an adapter that snaps into the front of your lens. Instead of being simple single lenses, each assembly consists of from three to four separate lenses of high-quality optical glass. The lenses are not designed for use on the standard 50-mm lens, but on a 200-mm or 300-mm focal-length lens. For greater versatility, a zoom

in the range of 70-210 mm or 100-300 mm works best. Depending on which lens you mount the assemblies on, you can reach magnifications of up to 8x.

Because of the high quality of the optics, the images are far superior to those obtained with normal Glose-up lenses.

EXTENSION TuBES AND BELLOWS

Another option is the use of extension tubes that are inserted between the lens and camera body (Fig. 12-2). They are usually available in sets of three, each of a different length. As with the diopters, they can be used individually or in com-binations. They have the advantage of being relatively inexpensive and add no more glass surfaces to degrade the image.

With a standard set of tubes and your normal lens you can easily reach a 1:1 magnification.

To achieve greater magnification, you can use a bellows, which is an

accor-Figure 12-3 Bellows for greater magnification than can be achieved with extension tubes.

dionfke expandable device attached to a set of rails (Fig. 12-3). The lens is attached on one end and the camera on the other. The front and rear standards are both movable and can be locked in place. Bellows are usually substantially longer than extension tube sets, and so higher magnifications can be achieved.

Between the two extremes of full exten-sion and retraction, the magnification range is continuously adjustable as opposed to the three set lengths of exten-sion tubes.

The best Bellows are those with a double rail system. One set of rails allows for magnification adjustment, while the other focuses by moving the whole cam-era-Bellows-lens assembly.

You can combine Bellows and exten-sion tubes for even greater magnification.

If you are mechanically inclined, much larger extension tubes can be made from such things as plastic pipe or the heavy cardboard tubes on which carpet comes

rolled (see Fig. A-3 in Appendix A). You must be careful to line the inside of the tube with black, nonreflective material such as cotton flocking or flocked paper.

This lining eliminates light scattered by bouncing around in the tube, which can create washed out "hot spots" on the photographs. Also, make sure that the image the lens projects covers the full frame at such an extension. If it doesn't, the corners will be cut off and the photograph "vignetted."