"Fogged" 4x5 as ND filter?

[poco]

So I've got some old techpan in 4x5 and I was thinking of exposing a few sheets to uniform light, developing to different densities and holding the result in front of my taking lens as different grades of neutral density filters. Is this a totally hare-brained idea? I regularly shoot through Ilford multicontrast filters as replacements for yellow and red filters and am satisfied with the results, so I don't see why shooting through the fine grained techpan shouldn't work. Or...?

[Louie Powell]

I guess I would need to be convinced that the fogging would be truly uniform before I would be willing to use fogged Techpan as an ND filter.

But I would not be at all hesitant to fix out the undeveloped film, wash and dry it, and then use it for dye-dodging negatives.

[poco]

Thanks, Louie.

I think if I throw a long lens onto the camera to guard against fall-off and shoot unfocused onto a piece of mat board, uniformity should be adequate. Then it's just a matter of even processing.

I'll give it a shot, anyway.

[Mark Sampson]

Tech Pan is discontinued, and being slow, should be good well past the expiration date. It might be easier just to find some Wratten ND gels on ebay and make pictures with the film.

[Helen Bach]

Here is what Kodak say in the Photographic Filters Handbook:

“Photographic film, uniformly exposed and processed, makes a good and relatively inexpensive attenuator for visible and infrared use. Because scattering is rather high, you cannot use this type of attenuator in an image-forming beam.”

Best,
Helen

[poco]

"“Photographic film, uniformly exposed and processed, makes a good and relatively inexpensive attenuator for visible and infrared use. Because scattering is rather high, you cannot use this type of attenuator in an image-forming beam.”

"cannot?"

Hmmm... sounds like a challenge to me.

Gonna try it with a couple sheets anyway and see what I get.

[C. D. Keth]

It works. I made a set of vignetters to fit a 4x5 mattebox on a film camera this way.

[Helen Bach]

"cannot?"

Hmmm... sounds like a challenge to me.

Yep, sounds like it to me as well.

Chris,

Was there any degradation in the darkened parts of the frame with your vignetter, or didn't it matter?

Thanks,
Helen

[roteague]

ND filters are cheap. Why go through this effort?

[poco]

Robert,

"Cheap" is relative to one's means. Besides, worst case is I'll learn something or other by trying it.