Color photography is not limited to live or solid subjects. You may occasionally be called upon to copy colored illustrations or even paintings.
A Faithful reproduction of an original picture or document is called “Copying” by photographic means. The original can be any printed matter. Drawings, handwritten document or continuous-tone originals like paintings, photographs, charts, engravings etc. This type of photography is not creative but it is purely technical in application. It does pose certain problems related to lighting, optics and processing.
When the original is too large or too delicate, we have to produce a photographic print or a slide that can be used instead of original. But the obvious reason is to make a large number of reproductions for distribution purposes. The problems involved are two-fold, covering on the one hand the technique of close-up photography, and on the other the question of correct color reproduction.
Invariably the approach is simply to have the original matter evenly illuminated, have the camera mounted perfectly square to the original, find the suitable exposure and process the film. Certain specialized subjects like old document, delicate manuscripts and rare paintings have to be handled with utmost care.
The subject must be kept flat, at right angles to the optical axis of the lens and parallel to the plane of the film. It is also possible to mount the camera on an enlarger and keep the original matter flat on the base-board of the enlarger. Today, most copying work is done by 35 mm cameras but for larger reproductions, roll-film cameras become essential. For really very large reproductions, even 4X5 inches cameras are employed.
The majority of cameras focus down to 3 or 4 feet, but no closer. This limit is inadequate except for copying large originals. To go nearer we therefore need some sort of close-up equipment.
With most amateur cameras the only way of getting closer to the subject is to use supplementary lenses. These are available in various focal lengths, and are usually marked in diopters. This is a reciprocal of the focal length in meters.
The lenses fit in front of the normal camera lens by means of suitable mounts, similar to filter mounts. With the camera lens set to infinity, the focal length of the supplementary lens also indicates the distance at which the subject will be sharp. Most supplementary lenses include focusing tables for the purpose.
These supplementary lenses are of course equally suitable for cameras which have no focusing movement, including box cameras.
With certain cameras, distance gauges are available which define the correct subject distance and the field of view covered. These are usually metal frames which are fixed to the camera and project in front of it, with the plane of the frame at the correct distance.
You can even make such a distance gauge at home. Set up the camera on a tripod pointing vertically downwards, open the back, and insert a piece of ground glass in the film plane. Place a large newspaper on the floor and lower the camera or raise it until the image of the printing is really sharp. Then note the extent of the field taken in and construct a frame of the same size or slightly smaller. Finally make a suitable connection by which to fit the frame in front of the camera at the right distance.
The ideal camera for copying is of course a double extension plate camera with a ground glass screen. This focuses over a continuous range from infinity right down to same size reproduction. The image is always visible on the screen and can be checked there for sharpness and for position. Such a camera is rather slower to use, but that hardly matters when you are copying. Color plates are of course not available, but you can use sheet film in suitable sheet film holders.
An almost equally efficient system consists of a single lens reflex camera with interchangeable lens, used in conjunction with extension tubes. The only drawback there is that the tubes cover one or two fixed ranges of subject distances instead of a continuous range. The image is however still visible on the focusing screen and can be checked there for maximum sharpness. With one or two cameras a bellows unit is available to take the place of the extension tubes; this provides a more continuous range of extension.
Certain miniature cameras include a reflex housing in their system of accessories; this fits in front of the camera in place of the lens and converts it into a single lens reflex camera. It can then be used with extension tubes or a bellows unit in the same way as already described.
For more ambitious work extensive copying outfits are available for selected cameras. These however are more specialized in their applications and are intended more for large scale and commercial establishments.
At this close range accurate focusing is essential; an error of a fraction of an inch will mean blurred pictures. If you can check the point of sharpest focus visually (i.e. on a ground glass screen, or with a supplementary rangefinder or similar optical means) adjust the focus setting in either direction from what appears to be the sharpest point. By gradually reducing the adjustments you will be able to bracket the range of correct settings and find the best one in the middle. With the ground glass screen especially it is often a little difficult to decide exactly when the image is sharpest; it may appear sharpest at a different point when you approach it from one direction than it would be when approached from the other. The method of bracketing therefore divides the possible error into half and places the theoretical point of sharp definition in the middle.
For copying, stop down the lens to the aperture of its optimum definition. This is not necessarily a very small stop, but tends to be about 1 to 3 stops below its maximum aperture.
The reason for this is not the need for depth of field we are after all photographing a flat subject and with reasonable care there should be no focusing error but to find a point at which lens defects and aberrations are at their minimum. The optimum aperture for copying may well be a half to one stop smaller than for normal photography; for the majority of lenses are computed to give their best performance at greater distances rather than with close ups.
Do not however stop down beyond the optimum setting for the definition may deteriorate. With better class lenses you can usually find out from a manufacturer what the best stop to use is. Alternatively make a few test exposures with the distance set correctly, and compare the shots for definition (e.g. our newspaper original) after development.
As in black-and-white copying, great care and accuracy are required in positioning the camera.
In the first place the camera must be properly centered over the subject so that the lens axis meets the intersection of the two diagonals of the original (which is usually rectangular).
Secondly the film plane must be absolutely parallel to the subject.
For single documents make sure that the image of the original covers the negative area fully, especially with 35 mm film. You cannot trim a 35 mm transparency!
If you are copying a complete book (e.g. art reproductions) on 35 mm film, it may be more economical to photograph two book pages on each frame.
According to the size of the original, two to six lamps will be needed.
You can use any artificial light source, but diffused light is best in practice. Photofloods, flash bulbs and electronic flash are thus preferable to spotlights.
Direct them at the subject at an angle of at least 45 degrees to the lens axis and at such a distance that the illumination is evenly distributed over the whole subject area.
To avoid undesirable reflections from shiny or semi-matt surfaces, carefully examine the area to be copied from the position of the camera lens, and see whether any of the lights are shining into the lens.
When using any form of flash, get an assistant to point a pocket torch towards the subject to be copied, at the same angle as each of the lights, while observing the effect.
Excellent copying is possible with a single flash gun. Yon simply fire flash bulbs in turn from each position where you would place a lamp for even illumination. Of course this can only be done in a dimly lit room, and is in fact open flash photography, with the shutter opened on the time exposure setting.
Special care is needed when copying shiny-surfaced originals. Here you have to observe the subject directly from all angles; the usual method of looking along the lens axis only is not sufficient.
When examining the image on a focusing screen, again do not only look along the lens axis; also inspect the corners of the ground glass where the oblique rays strike it.
In order to standardize working conditions and facilitate the setting-up of equipment, it is a good idea to mark out the positions of the copying easel and the lamps on the studio or workroom floor.
The most important aspect of copying is to ensure uniform lighting over the whole surface of the illustration, painting, tapestry etc., to be photographed. Check this by means of an exposure meter.
The best method of measuring the light distribution is to use a piece of white card (e.g. the back of a sheet of photographic paper), or better still get a test card with one side white and the other neutral grey.
Hold the white card over each corner of the document in turn, and then over the centre, measuring the light reflected in each position with an optical photometer or reflected light meter. Keep the meter at the same distance from the card each time, and make certain that it does not cast a shadow on the card.
With a reflected light meter, measure the intensity of the light reflected by the white card in each position.
Incident light meters are well suited for checking and adjusting the evenness of illumination, as the incident light is unaffected either by the different colors in the subject or by any reflections from shiny surfaces such as a protective glass covering.
The various types of meter are handled in the usual way when it comes to measuring the exposure.
Take reflected light readings from the subject itself, or from a grey card in the same position. Alternatively, use a white card at the subject position and divide the exposure obtained by 5, as the average subject reflects only 20 per cent of the incident light.
The grey card is a useful cross-check on the overall brightness of the original; if it appears brighter to the eye than the subject, open the lens aperture by a quarter to half a stop; if darker, stop down by the same amount.
As most copying work is done in close-up, you have to allow for the extra lens-to-film distance, which reduces the effective lens aperture, when calculating the exposure.
In black-and-white photography, you rarely have to allow for that fact, except at very close range, as the latitude of the film covers minor variations. With the limited exposure latitude of color material, however, an exposure correction factor is necessary as soon as the subject is within a distance equal to ten times the focal length of the lens in use.
With the standard 2-inch lens fitted to most miniature cameras, there is therefore no need to increase the exposure for objects beyond about 2 feet, but longer focus lenses (either telephotos on miniatures or standard lenses on larger cameras) are more critical.
Additional exposure may be given either by opening the lens aperture wider or keeping the shutter open longer.
Polarized light can help to increase the brilliance of the colors, eliminate reflections, especially when copying oil paintings, and to improve texture definition of objects photographed in close-up. For this purpose you need fairly large polarizing filters placed in front of the lamps.
The position of the lamps in relation to the camera may be varied at will. A corresponding polarizing filter is also placed over the camera lens.
This combination can suppress reflections even if you are pointing the camera squarely at the plane of the painting to be copied.
Such a filter combination requires one-and-a-half to two stops more exposure.
It is almost impossible to obtain an absolutely correct color rendering when copying a painting or colored illustration. The reason for this is that the spectral characteristics of the pigments of the original hardly ever match those of most current color films, and a certain amount of color distortion is inevitable.
However, to achieve the best compromise make sure that the lighting accurately matches the film. Thus use Photofloods with type A film, clear flash bulbs with type F film, or blue bulbs with daylight film. Avoid daylight itself which is too variable. Electronic flash and clear bulbs by themselves, too, may not be sufficiently accurate in their color match to the film.
Close-up photography is of course not limited to copying pictures, but covers a far larger field of small and tiny subjects. You can record the varied shapes, colors and tones of plant and animal life with a wealth of detail normally invisible to the naked eye. You will in fact find yourself in a completely new world.
Strictly speaking macro-photography implies life size or larger images of small objects. It is however commonly taken to include smaller scales of reproduction too, and from the point of view of photographic technique anything larger than one-quarter life size qualifies for macro-photography.
The camera equipment is basically the same as for copying, but in view of the very close distances the simpler focusing methods are less suitable. Thus ordinary supplementary lenses are no longer adequate unless they are combined with precision distance gauges or close-up rangefinders. On the other hand a reflex camera with extension tubes or a miniature camera with a reflex housing is ideal for this purpose.
When focusing ultra close-ups, it becomes increasingly difficult to find the ideal point of sharpness on a ground glass screen. In such a case it is therefore better to move the whole camera forwards and backwards from the subject rather than adjust the lens. The transition from sharp to unsharp then becomes very much more sudden.
Unlike originals for copying, close-up subjects have a certain depth and therefore need a small lens aperture to provide sufficient depth of field. Even so, when you are taking something life-size, the depth of field with a medium aperture may be no more than a quarter inch.
With a copying gauge, position the camera in such a way that the centre of the subject is in the plane of the gauge.
For all close-up work of this type a firm support, preferably a table tripod or stand, is highly desirable. While hand held shots are possible at instantaneous shutter speeds, there is a risk that you may move out of focus accidentally.
For live subjects choose a shutter speed of 1/25 second or faster. With motionless objects and a firm support time exposures are quite feasible. Remember, however, that seemingly static subjects may move; thus plants out of doors tend to sway about in the wind unless you put suitable screens round them.
As in copying you have to increase the exposure for these ultra close-ups to compensate for the increased lens-to-film distance.
Plants and animals such as insects, lizards, and so on, are suitable for this type of work, provided they can be made to keep in one place. With more active creatures you may have to use either chloroformed or dead specimens (e.g. butterflies) which may be positioned on suitable flowers and the like.
You will often need independent lighting or at least supplementary illumination. Electronic flash is ideal because it matches daylight in color quality and permits short exposure times. Photoflood and similar lamps are less suitable; the heat given out by the lamp at such close range may easily cause plants to wilt and may even kill the insects. The most useful arrangement is a single flash unit directed on a main area of the subject, with white card reflectors to brighten up shadow areas.