Figure 58 is a photograph of two cans for popular brands of tobacco and a \Vratten color chart. This exposure was made on commercial film, minutes exposure, f32. The red can is here shown black and you have prac tically no values in red, yellow-green and green, but blue-green, blue and violet are light. In other words, it is a color blind film.
Figure 59 is the same set-up made with commercial ortho film, K2 filter, same stop, eight minutes exposure. We are still short on the reds, hut have a good correction in the yellow, yellow-green, blue-green, blue and violet. You will notice from this that this particular film is not sensitive to red to any marked degree, but is very good for set-ups where there are no greens or deep reds. The multiplying factor for commercial ortho film and K2 filter is about fifteen times, that is, behind a K2 filter commercial ortho film requires fifteen times as much exposure as it does with no filter, which is the only drawback I can see to this film.
Figure 60 is the same set-up made with Wratten panchromatic plate, no filter, the same stop, exposure 30 seconds.
As can be seen from the chart, we have a fairly good separation even with no filter. The deep red in the Prince Albert can is still short, but, nevertheless,
shows the advantage of this plate even without a filter, in that it can be used many times for interiors and set-ups in the studio without a filter and yet get fairly good separation without prolonged exposure.
Figure 61 is made on a Wratten plate, K3 filter, same stop, exposure four minutes. This gives what the commercial photographer would call full correc tion.
Figure 62 is made with the "B," the green filter, exposure five minutes, same stop. The Tuxedo can with that exposure is still a little dark, but by a prolonged exposure, it could be made light.
For those who wish to go into this subject deeper, for the theory, I can recommend the following books: "The Photography of Colored Objects," by Dr. C. E. Kenneth Alees. "Color Plates and Filters for Commercial Photography," Eastman Kodak Company.
"Dry Plates and Filters for Trichromatic Work," G. Cramer Dry Plate Co. "The Photographing of Color Contrasts," G. Cramer Dry Plate Co.