Can a filter on panchromatic B&W film mimic orthochromatic film tonality?
Asked 7/30/2019
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Orthochromatic film is sensitive mainly to blue and green light and largely insensitive to red, which is why reds can render much darker than they do on panchromatic film. Can this look be approximated by using a filter on modern panchromatic black-and-white film? Would a blue filter work, or would a cyan/blue-green filter be closer since ortho film also responds to green? I'm interested specifically in tonal rendition, not necessarily matching grain or other film characteristics.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
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You can simulate the spectral response with filters. To cut red, use a cyan or blue-green filter. To select for blue or green, use a blue or green filter. If you can find the response curve of the films you're interested in, you can look for corresponding filters. Otherwise, you should shoot some test rolls to compare filters against.
You can see density curves for Kodak filters. Some recommend trying a Wratten 44A filter. (Light blue-green. Minus-red filter.)
For comparison, here's the curve of the Kodak 38A filter. (Blue. Absorbs red, some UV, and green light.)
You cannot use filters to emulate other aspects of the film, such as fine grain with high contrast. Since filters cut light, you may see increased grain. You could try pushing to increase contrast (at the cost of increased grain) or pulling to decrease grain (at the cost of decreased contrast).
Originally by user75526. Source · Licensed CC BY-SA 4.0
user75526
6y ago
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Yes—partly. The main tonal difference of orthochromatic film is its low sensitivity to red, so putting a red-blocking filter on panchromatic film can approximate that aspect.
A blue filter will suppress reds, but it also cuts much of the green and yellow light, so it may not match ortho film as well as a cyan or blue-green filter. A cyan filter is often the closer match because ortho film is sensitive to blue and green, not just blue.
If you can find spectral response curves for the ortho film you want to imitate, compare them with transmission curves for filters and choose accordingly. Some photographers suggest trying blue-green/minus-red filters such as a Wratten 44A; a stronger blue filter like an 38A would remove more green as well.
What filters cannot replicate are other film traits such as grain, contrast curve, and overall “look.” Because filters reduce exposure, they may also increase apparent grain if you compensate by pushing or underexposing. So: yes, you can get closer in tonal response, but not perfectly duplicate ortho film in every respect. Testing a few filters is the practical way to judge the result.
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