PHOTOGRAPHY OF COLORED OBJECTS For a great deal of the modern commercial, technical and scientific photography, color sensitive plates and filters are practically a necessity—in fact, it might be said that they are a necessity. While it is true, old time photographers got really remarkable results without plates sensitive to red and the deeper greens, the modern photographer will get far better results much more quickly.
It is a known fact that all dry plates are sensitive to red to a more or less degree and by giving a prolonged exposure, sometimes running into days, it was possible to get a sort of negative and, by skillful printing, dodging, staining, etc., a fairly nice print was obtained. But, all that for the past. Today, the commercial operator gets negatives with any desired correction or separation, gets them quickly, and he has the satisfaction of knowing they will be right and of knowing it in advance of his exposure.
If you are doing work for photo-engravers, lithographers, commercial artists, etc., you will oftentimes have what are known as separation negatives to make, that is, where one or more colors are completely eliminated, but the most of the work will be correction, which is rendering the colors in proper tone in monochrome.
There have been so many very good articles and books written on this subject, and it has been the topic of so many demonstrations and so much dis cussion, that it is not in the sphere of this limited article to go into the theory of it. I will discuss it from the practical side and try to overcome some of the little difficulties that are met with from time to time.
\Vhile there are several very good panchromatic plates on the market, the \Vratten .and the Cramer Spectrum are probably the leaders, and it has been the experience of the writer that, though others might be very good for some purposes, they are not the all-around plates that the two just mentioned are, and it never pays to use anything but the best.
The \Vratten is a backed plate and gives most excellent results under any and all conditions. The one drawback to panchromatic plates, however, is that the manufacturers have been unable, up to the present time, to make them absolutely uniform in speed for all filters. For this reason, with every box of
Wratten plates, there is an exposure card (See Figure 57), and as the exposure figures change with different emulsions, before making any exposure, especially with reds, it is Nell to consult the card accompanying the plates for that particu lar emulsion being used. I find that many operators pay absolutely no attention to these cards. That part is important if you are going to "bring home the bacon" and eliminate waste.
When to use a panchromatic plate and filters will be governed by the result it is desired to obtain. They should be used for studio work such as pianos and furniture finished in red, merchandise set-ups for catalogue work containing reds or deep greens and for photo-engraving color work.
When photographs are to be hand colored, panchromatic plates are more of a necessity than ever to give the proper color correction.
Outside of the studio you will need them on all cases where a correct color rendering is wanted, and many times a light yellow filter will be used with a yellow sensitive film or plate to eliminate the blue haze—especially is this true in mountain scenery and seascapes, snow work and in making pictures from high buildings and what are commonly called birdseye views.
There is a tendency among some workers to overdo outside correction, that is, to use too deep a filter. While it possibly is right to correct your blue sky down to a gray, nevertheless, there are very few customers who really like a dark sky, even if it. has clouds in it, and we must remember that we are not selling the sky as yet.
The kind of filter to use and its position either before the lens or in back of it, or in between, is somewhat of an important matter. You should always use the filters made for the plates being used, that is, do not use Cramer filters on \Vratten plates, and vice versa, and expect to get real results. I have worked in studios that used home-made filters and they seemed to work all right, but I have never felt really safe as I would with regular filters.