Making pre-filtered B/W film

DaveTheWalker · Nov 16, 2017

Hello,

A thought occurred to me whilst driving this morning. Various B/W films have different sensitivities to coloured light (orthochromatic, panchromatic, etc..), but all are sensitive to blue light (as it's the higher-energy photons at that end of the spectrum).

When taking photographs, it is common to add a yellow or orange filter over the lens to reduce some of this blue-sensitivity and improve the pictorial qualities of the film for landscapes etc..

I wondered if it might be possible to include this yellow filter on the film itself, as a top coating layer? I'm sure the Lomo crowd would go nuts for various films pre-filtered with yellow, orange or red coatings.

Anyway - just a thought... does anybody know if it would be possible/easy?

Dave

Anon Ymous · Nov 16, 2017

TMax 400 has reduced blue sensitivity compared to a typical bw film.

BrianVS · Nov 16, 2017

What you are describing is color negative film with just one dye layer- so it is certainly possible to do. When printing the negative- the yellow dye-layer will also affect exposure and contrast on the paper. That might be an issue.

It also limits filter selection by film type, rather than using a filter over the lens. I keep a series of filters in the bag- y44/y48/y52/o56/r60. Plus... they make the camera look way more cool. (not really- they are warming filters)

Svenedin · Nov 16, 2017

So are you suggesting some kind of coating over the emulsion that behaves like a yellow filter over the lens? If this is possible then the film would no longer be general purpose. At least with over the lens filters there is a lot of flexibility in the filters used.

dE fENDER · Nov 16, 2017

There were some sensitizers with such effect - reduced blue sensitivity:
Pinortol I - mix of the pinachrom sensitizing dye with yellow filtering dye - acrydine yellow (or sometimes another yellow dye).
Pinortol II - mix of the pinacyanol sensitizing dye with the same yellow filtering dye.
So if you can coat one layer emulsion - you can try to experiments with such sensitizers (pinacyanol is quite available).

BrianShaw · Nov 16, 2017

One question I always ask (sometimes of myself) when encountering perfectly rationale questions like this: Why didn't they do something like this in the past. There is a long history of film photography in which this either wasn't enough of an issue, or for some other reason not worth doing.

In terms of ideas for the future... fun to think about but not sure I'd be happy paying more (assumption on my part) for film when all I'd personally get out of it is a redundant filter or two.

But theoretically, I can imagine B&W film being offered with a number of SKUs: B&W-T (traditional bias); B&W-8 (natural bias); B&W-21 (moderate contrast bias); B&W-25 (heavy contrast bias); B&W-11 (Forest and garden bias).

dwross · Nov 16, 2017

Once upon a time (and today, if you make your own emulsions) "screened" plates were common. A yellow dye (almost always tartrazine) was added directly to the emulsion. It knocked back the relative blue sensitivity of orthochromatic plates. It also severely reduced the speed of already slow plates. When panchromatic emulsions came along, and filters got better and cheaper, screened plates fell out of fashion. As mentioned above, modern panchromatic films are much better balanced for sensitivity. Having a few filters in your pack can give you all the exposure flexibility you could ask for.

DaveTheWalker · Nov 16, 2017

Thanks for the comments so far. I agree that it wouldn't necessarily be terribly "general purpose", nor appealing to those with a variety of filters, but I just thought it may impart a certain "look" to a film, that would appeal to the sort of people who buy those funny special films: Dead Link Removed as well as those who just like trying new things and don't already have a set of filters.

On top of all that, it might just be fun

Buoyed by the comments by dwross, I may experiment with "staining" a 35mm roll in tartrazine, which seems very easy to get hold of, and inexpensive. If I try it, I'll be sure to report back how it goes! Actually, I may start off with 5x4 sheet film, so I can test it on a per-shot basis.

I'm not expecting it to have wide appeal - it just piqued my interest as a possible experiment.

AgX · Nov 16, 2017

DaveTheWalker said:
When taking photographs, it is common to add a yellow or orange filter over the lens to reduce some of this blue-sensitivity and improve the pictorial qualities of the film for landscapes etc.

It rather was common when green and red sensitivity was not optimal and speed for quite some some part was based on that blue sensitivity. Back then a yellowe filter was a standard accessory.
Today films have much more equalized spectral sensitivity, though there still are variations. But adding such niche film as you describe would likely be not feasable economically to the manufacturers. I assume most users would rather prefer a more universal film and rather would add a yellow filter when necessary.
However, there still is a market for orthochromatic films, although that effect can be achieved with panchromatic films and the use of a filter too.

thio · Nov 16, 2017

It was/is a common practice - additions of the filter dyes ito to the emulsion layers (both for BW and color films). It was invented by Lumiere Bros. in the 1900-1910s!

DaveTheWalker · Nov 16, 2017

thio said:
It was/is a common practice - additions of the filter dyes ito to the emulsion layers (both for BW and color films). It was invented by Lumiere Bros. in the 1900-1910s!

It wouldn't be the first time I "invented" something that was already over 100 years old

darkroommike · Nov 16, 2017

At one time you could buy blue sensitive, orthochromatic (maybe a couple of different types?), at least three kinds or panchromatic film and IR. The problem all of these share is that they only "see" one way. Let's say you buy a roll of "yellow filter" film and decide half way through the roll that you now need "blue filter" film. What do you do? If I shoot with glass filters on my lens I can merely unscrew one filter and screw on another.

tedr1 · Nov 16, 2017

Perhaps what the "Lomography" enthusiasts need is not filtered film but cameras that accept accessories. This is re-inventing the wheel, it has been done with 35mm and 120 cameras. These cameras are now sold for peanuts. Perhaps what "Lomographers" need is an ability to learn about photographic equipment?

voceumana · Nov 16, 2017

Originally films were only sensitive to blue light, then dyes were added to make them sensitive to other colors. Having a top filter coating is certainly possible.

Polaroid introduced a 35mm color slide film for instant processing; the film was a black and white film, but the base had colored lines running the full length of the film, finely spaced. Exposure was made through the base, so the lines acted as filters and the film area adjacent to the line was exposed only by red, green, or blue light. The lines acted as filters when projecting, so the color image was reformed on the screen. If you got close to the screen you could see the individual lines.

Sirius Glass · Nov 16, 2017

Your time would be better spent developing a filter that improves the composition as the photograph is taken, even moving objects to better positions. I would buy one of those filter for each of my many lenses.

Making pre-filtered B/W film

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