This section is from the "Studio light a magazine of information for the profession 1918" book, by Sara F. T. Price. Also see Amazon: Studio light a magazine of information for the profession 1918.
It is easy for the photographer to follow a rut, to say he is only interested in straight photography and cares nothing about difficult work that occasionally comes to him. "Let the other fellow bother with it," is the easy way out, to be sure, but the photographer' s ability is often measured by the difficult thing he does well, and business turned to him in this way more often than not sticks to him when other work is wanted.
For example, a professor of plant pathology had a number of specimens he wished photographed and the ordinary means failed to produce a satisfactory result. They were green leaves on which appeared reddish brown spots caused by some plant disease. The photographer had used ordinary plates and even ortho-chromatic plates and yellow filters and failed.
But he didn't give it up. He called for help and was quickly advised that a panchromatic plate and green filter would give the desired result, and so it did, as will be seen by our illustration.
The panchromatic plate is specially sensitive to red and green and as the green filter absorbed the red and transmitted the green the red marks on the leaf photographed dark and the green body of the leaf light and full of detail. The result was perfectly satisfactory.
If it had been a red leaf with green markings exactly the same result would have been produced by using a red filter. The red filter absorbs blue and green and transmits red, so that with a plate sensitive to red (panchromatic) and a red filter, red objects photograph light, and blue and green objects dark.
Yellow filters are specially useful but not when it is desired to over correct green or red, that is, make green or red objects photograph lighter than they really are. Yellow light is a combination of green and red and absorbs blue. For this reason yellow filters are especially suitable for cloud rendering. The blue light is absorbed by the filter and as it doesn't reach the plate any blue sky in the picture is rendered much darker than the white clouds.
Yellow filters transmit their own color, so they are useful in photographing furniture. The yellow grain of the wood is rendered as light as it appears to the eye, but the plate used must be one that is sensitive to yellow. Yellow filters give good results on orthochromatic film or plates because they are sensitive to yellow and slightly to green.
A yellow filter and orthochromatic film or plate will not give a correct rendering of red. To photograph red as other than black the emulsion must be red sensitive. Yellow filters are very useful with panchromatic plates. They give the most generally satisfactory rendering of all colors when it is desired to have a number of colors in a single object appear in monochrome as they appear to the eye.
Of course a photographic plate cannot show color contrast, but it can show tone contrast and this the panchromatic plate will do perfectly with a K3 filter. If a light red object is photographed against a dark blue background the red will appear lighter than the blue, while if the blue and red are of the same strength they will photograph as the same shade of grey. A bright red against a dark green will likewise appear a light grey against a dark grey.
But this order can be reversed by using contrast filters and panchromatic plates. A red object against a green background of the same strength can be made lighter than its background if a red filter is used or darker than its background if a green filter is used.
Blue filters are seldom used because all plates are so much more sensitive to blue than to other colors that blue is as much over-corrected by using an ordinary plate without a filter as red is over-corrected by using a panchromatic plate and a red filter.
FROM AN ARTURA IRIS PRINT
By Fred H. Reed Wichita, Kans.
Even panchromatic plates are super-sensitive to blue and require at least a light yellow filter such as the K 1 or K 2 for best general results or the K3 for absolutely correct rendering of all colors.
With these things in mind it is quite simple to secure almost any result within reason by using panchromatic plates and filters. There is nothing difficult about such work and and it is certainly gratifying to succeed where you have previously failed.
Panchromatic plates and filters are very useful in copying stained prints or in reproducing valuable stained negatives.
If a print has an objectionable yellow stain, no trace of the stain will be seen in a negative made through a filter of a yellow slightly darker than the stain. The same is true of a yellow stained negative from which it is impossible to secure a good print. Make a positive through a filter darker in color than the stain in the negative. The G filter, a dark yellow, is generally used for this purpose. If the stain is red, use a red filter - if green, use a green filter.
Our illustrations show a number of interesting comparisons of work on ordinary and panchromatic plates, with notes of the filters used. Try a piece of difficult work for yourself, using an ordinary plate, then a Wratten Panchromatic plate and the proper filter. You will find it so easy to secure good results that you will never be without Wratten Panchromatic Plates and Filters.
There is no lack of food, fighters or photographers in Kansas and, of the latter, Mr. Fred H. Reed of Wichita is one of those who are well known and universally liked. He has an excellent business, makes clean cut, bread and butter portraits that please the people and help to make photography popular.