There is another branch of handwriting photography—the detection of erasure in, for instance, a check or a The procedure on a job of this kind is to make a direct enlargement of the place where the erasure is sus pected, including enough of the surrounding paper to use it as a comparison.
It might be well to mention, before going any further, that there is con siderable difference between a direct enlargement and an enlargement from a negative. In making a direct enlargement, the texture of the paper, the shading, in fact, every minute detail, is enlarged correspondingly, while, if a negative same size or a reduction negative is made, the texture, for instance, is lost to a more or less degree, according to the reduction, and you cannot enlarge something you have not got on the negative.
If a chemical has been used to eradicate the original handwriting, the substituted wording can generally be detected by the difference in the shades of ink used when enlarged directly.
This is where a moving picture lens, of a focus of say two inches, comes in very handy, for you will have bellows enough on an ordinary studio camera to make an eight, ten or twenty times enlargement direct.
The photographing of finger prints is sometimes rather disagreeable, as you will be called upon to photograph them in almost inaccessible places. Finger prints on light surfaces are more readily photographed by dusting on a little finely powdered lamp-black or graphite and then carefully blowing off the surplus powder. If on a black surface, it means they will have to be whitened. One way to do this is to dust on a little powdered calomel. This will bleach them out fairly white, and with a rather contrasty plate good results can generally be obtained.
Most railroads, street car and other public utilities corporations, which are liable to a lawsuit in case of an accident, have numerous photographs made of the scene of an accident directly after it occurs, so that they can reconstruct the place and put things back to normal, and when the time comes for a suit, they will have an accurate record of the conditions at the time of the accident. This photography is generally done under the supervision of a claim agent and usually simply means following his instructions and the making of good clear photographs. All plates should be numbered and accurate account kept
of the distance from point photographed to the camera, time of day, etc. This is really profitable work, for it is quickly done and they do not care what you charge if they can rely on you and have confidence in your getting results, but they certainly do not want to bother with a fellow who is the least bit hesitant about his results, as oftentimes photographs cannot be remade.
There is considerable litigation connected with conditions of metals, such as used in bridges, boilers, engines, etc., which have gone bad. This is as a rule in the sphere of the metallurgist and he will be the proper man to direct the making of the photographs. It is usually a case of direct enlargement up to thirty and forty diameters and in special cases 250 to 500 diameters enlargement, although this latter is a high tnagnification and is, of course, done on a photo-micrographic outfit.
Then, there is the photographing of old documents, such as records of inventions, old deeds, and the like. This is always better done on a panchro matic or yellow sensitive plate with a G filter of the Wratten series, and by the use of this combination, you can gct the paper to photograph nearly pure white, thus darkening up the ink enough to make it photograph black, which is about all there is to a job of that kind.
The type of lens to use on legal work is important. It should always be an anastigmat—the more free from astigmatism the better. Some photog raphers, who make a specialty of legal work, have their lens tested by the Bureau of Standards, at Washington, D. C., which, I believe, charges only a nominal fee for the work and tells the true condition of the lens.
The kind of plate to use will be governed by the work and conditions, but generally speaking, a slow plate, such as the Hammer Slow, Seed 23 and Cramer Slow, is to be preferred to the more speedy makes. As mentioned herein, Panchromatic plates will be found very satisfactory for copies, but the general rule of it is to use as slow a plate as the job will stand, as results will be far more hrilliant and clear.