This section is from the "Studio light a magazine of information for the profession 1923" book, by Sara F. T. Price. Also see Amazon: Studio light a magazine of information for the profession 1923.
The "snap" or "pep" in a negative may be due only to its contrast, in which case quality may be lacking, or it may be due to a combination of contrast and gradation in which case quality is combined with brilliance or "pep."
The point we want to bring out is that the "pep" you require in a brilliant portrait negative is not regulated by the contrast of the material on which the negative is made. In fact a material having considerable contrast can not produce a quality negative.
Just here we will explain what we mean by quality and the difference between quality and contrast, as these two terms have very definite applications to sensitive, negative-making materials.
We will suppose that you have an object to photograph having forty distinct tones ranging from white to dead black and you use a film or plate having so steep a scale of contrast that it can only register twenty of these tones. You can at once see that the material has twice as much contrast as it should have to correctly reproduce the object photographed.
On the other hand we will suppose that you use a material, such as Portrait Film, having a scale of contrast not nearly so steep but much longer. You have two decided advantages. The shortest correct exposure will register all of the forty tones. Give double the exposure and you will still have the forty tones in correct relation to one another but all having slightly more density. Give three or four times the first exposure and you will still have correct contrast between the tones, the negative having merely climbed higher on the ladder of density.
The negative having normal exposure or the one having four times normal exposure will each give a perfect print, the increase in density only increasing the exposure necessary to make a print. Reduce the dense negative and it will be identical with the one having normal exposure.
This long contrast or gradation scale which permits of the reproduction of an exceptionally long scale of tones and which also permits of great latitude in exposure without altering the contrast of the subject is what we term quality.
One of the fine things about the remarkable quality of Portrait Film is that you can produce practically any result you wish. You must not make the mistake, however, of expecting it to falsify results. If you are accustomed to making a lighting considerably lower in key than you wanted your negative, because you knew the material would increase the contrast, you must raise the key of light for Portrait Film.
PORTRAIT FILM NEGATIVE, VITAVA PRINT
By D. D. Spellman Detroit, Mich.
Put "pep" in your lighting and you will get "pep" in the film negative. And just here is another film advantage. It is almost impossible to make a lighting in a key that is too high for Portrait Film to record. You can let the sunlight fall directly on the subject and still get detail in highlights and shadows.
Loss of highlight detail is often directly due to halation. No matter how small or how large the highlight there should be some detail, and this detail in highlights is almost invariably destroyed or at least greatly degraded by the halation produced by the glass plate. The light passes through the emulsion and is reflected from the back of the glass, the spread of the halation depending upon the thickness of the glass.
For this reason the man who uses glass plates holds his highlights down and depends upon the contrast of the plate to give him "pep" at a loss of quality.
Film is so thin that there is no chance for the light to spread, hence, the absence of halation in film negatives.
Don't be afraid to put "pep" in your lightings, use Portrait Film and you will get all of the brilliance of your lightings plus real portrait quality that can be reproduced in your prints.