orthochromatic film?

[Doremus Scudder]

Pardon me if this is an ignorant question: Could a person get an effect similar to using ortho film by using a blue filter with panchromatic film?

The Wratten #44 is a "minus-red" filter. When used with pan film in daylight, it will give you a tonal rendition like an ortho film. A blue filter, like a #47, will give more extreme effects.

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2. There is NO filter which will give you the same film sensitivity and color response as orthochromatic film ,or vice versa. There are many suggestions from workers with little or no experience with ortho film.
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Let's be a bit more specific here.

Ortho film almost certainly has different characteristics than filtered panchromatic film, which make it unique. (I'm sure different ortho films have characteristics slightly different from one another too; it's just that these days, the choices are rather limited...)

That said, one can approximate the spectral sensitivity of orthochromatic film by using red-blocking filters with pan film. The end result, i.e., the exact spectral sensitivity, of the filtered pan film will, of course, depend on the exact filter used and the spectral sensitivity of the film used. Still, the effects obtained by using red-blocking filters on pan film can be gratifying and one doesn't have to carry extra film, just some filters.

And, let's differentiate between older blue-sensitive emulsions and orthochromatic emulsions. The former are the "original" photographic materials, the silver halides alone, which are only sensitive to blue light, not green or red. Later, emulsion formulators learned to add sensitizing dyes to the emulsion to make it sensitive to green as well as blue. These blue-green sensitive emulsions were named orthochromatic. Even later, when components were found to make film sensitive to blue, green and red, thus better approximating the visual spectrum, panchromatic emulsions became common.

So, filtering the red out of the light reaching a panchromatic emulsion gives a similar spectral response as orthochromatic film (Jim, note I'm saying "similar," not exact ). The classic minus red filters are the Wratten #44 and #44A, which were originally used in color separation work. Ansel Adams recommended those filters for approximating the effects of ortho film with panchromatic emulsions. Optical-quality cyan filters will block red and can be used for the same purpose as well. The effects will vary depending on exact spectral characteristics of the filter and film. And, I've had pretty good luck getting an ortho effect on pan film using the 80A and 80B color-conversion filters. They look blue, but pass quite a bit of green and a bit of red (they were originally intended to convert tungsten light into something better approximating daylight when using daylight-balanced films, especially transparency materials, with tungsten lighting, which is much redder).

Using a Wratten #47 filter or similar, that passes only blue light, will give an effect more similar to the old blue-sensitive emulsions, as they don't pass any green light. They are also a useful tool, but will not, strictly-speaking, give the "orthochromatic effect" that other filters that pass green as well as blue do.

An interesting read on the specific application of using filters to obtain an "ortho look" would be to find the thread over at Photrio started by Jarin Blaschke here: He was the cinematographer for the award-winning film "The Lighthouse" and had filters specially made for his cine film (Plus X?). He eventually had filters specially made to suit his needs.

Best,

Doremus