Darkslide Modification for Film Testing

Tobywan · Sep 8, 2014

I got the idea the other day to take some extra darkslides that fit my film holders and modify them so when I test film, I won't use a whole sheet.
Took 2 darkslides and cut 1-5/8" 2-1/8" openings, one on the left side top, the other on the right side top. This way I can get 4 tests on1 sheet of film. After cutting the openings, I slightly beveled them and sanded everything with 600 grit to make sure nothing caught on the light seals. The slides inserted in the holder OK but when I tried to remove them, they caught on the seal. I was able to slide a piece of film in between the slide and the seal to remove them.
Has anyone else tried this or how do you get more than 1 exposure on a piece of film?

MattKing · Sep 8, 2014

I believe you need two different darkslides that are each "flippable" in order to get four tests on one sheet.

If you have two openings in the same dark slide, how are you going to expose through one opening, without exposing through the other?

Tobywan · Sep 8, 2014

Sorry, I should have explained better. 1 opening on each darkslide.

Old-N-Feeble · Sep 8, 2014

You could try making the vertical edges of the holes slightly rounded (wider toward the center) such that the light seal isn't fighting against a flat edge. Even then you'll probably wear out the seals much faster than using regular slides. However, that may not matter since you'll be saving quite a bit of money on film tests so sacrificing a film holder is probably worth it. Anyway, the rounded trailing edges should mostly eliminate the sticking issue.

Sorry for the lousy drawing...

wildbill · Sep 8, 2014

or you could just pull the slide out 1/4 of the way, make an exposure, pull another 1/4, make an exposure, pull another 1/4, make an exposure, etc. You just have to do a little math, no cutting your slides.

ChuckP · Sep 9, 2014

I use 3 dark slides each with an approx 1" hole drilled in it. The holes are offset so they don't overlap. Flipping the slides you get 6 exposures per sheet. Various types of this method are pretty common and I'm sure I found out about mine from a magazine article or book. Problem I can see is does your lens cover a sheet of your film uniformly. If not changing the position of each test on the sheet may not be accurate. I did get a bunch of ND filters cheap so I started using them to vary exposure rather than changing f-stop or shutter speed. But I suppose you don't need to be that accurate. Especially now with VC papers. How you point your meter is probably more important.

E. von Hoegh · Sep 9, 2014

Tobywan said:
I got the idea the other day to take some extra darkslides that fit my film holders and modify them so when I test film, I won't use a whole sheet.
Took 2 darkslides and cut 1-5/8" 2-1/8" openings, one on the left side top, the other on the right side top. This way I can get 4 tests on1 sheet of film. After cutting the openings, I slightly beveled them and sanded everything with 600 grit to make sure nothing caught on the light seals. The slides inserted in the holder OK but when I tried to remove them, they caught on the seal. I was able to slide a piece of film in between the slide and the seal to remove them.
Has anyone else tried this or how do you get more than 1 exposure on a piece of film?

I have a Deardorff V8, which takes splitter boards. You can make 2x 5x8, 2x 4x10, or 4x 4x5. I f your camera won't take boards, you could make thin cardboard masks perhaps.

Jim Noel · Sep 9, 2014

ChuckP said:
I use 3 dark slides each with an approx 1" hole drilled in it. The holes are offset so they don't overlap. Flipping the slides you get 6 exposures per sheet. Various types of this method are pretty common and I'm sure I found out about mine from a magazine article or book. Problem I can see is does your lens cover a sheet of your film uniformly. If not changing the position of each test on the sheet may not be accurate. I did get a bunch of ND filters cheap so I started using them to vary exposure rather than changing f-stop or shutter speed. But I suppose you don't need to be that accurate. Especially now with VC papers. How you point your meter is probably more important.

This is the method I have used successfully for 20+ years.

Maris · Sep 9, 2014

wildbill said:
or you could just pull the slide out 1/4 of the way, make an exposure, pull another 1/4, make an exposure, pull another 1/4, make an exposure, etc. You just have to do a little math, no cutting your slides.

Absolutely! I've calibrated cardboard rulers that indicate the amount of darkslide pulled so I can lay 5 or 10 stepped exposures on a single piece of film. The math uses exposure units in the sequence 1,1,2,4,8,.... By cutting the film into four strips and developing each strip for a different time I can get 10 exposures at 4 different dev times. That's a lot of information from a single piece of film!

peter k. · Sep 9, 2014

Well different folks different strokes... I do nothing with the film holder or the dark slides.. just with the film.

I've done this constant number of times, all you have to do is cut as many as you want to try. Cut a 4x5 in half. That gives you two. You also cut an old, exposed, 4x5 in half, as a filler. Filler goes in first, with scotch tape over both ends. this clarifies the test sample when getting ready to develop, as it has no tape on it, and also keeps the unexposed test, from being pushed over or jammed unto the old exposed filler.

Once for a lens test, I centered the 1/2 (4x5) sheet in the center, with fill on both ends.
Very simple ...

RalphLambrecht · Sep 9, 2014

Tobywan said:
I got the idea the other day to take some extra darkslides that fit my film holders and modify them so when I test film, I won't use a whole sheet.
Took 2 darkslides and cut 1-5/8" 2-1/8" openings, one on the left side top, the other on the right side top. This way I can get 4 tests on1 sheet of film. After cutting the openings, I slightly beveled them and sanded everything with 600 grit to make sure nothing caught on the light seals. The slides inserted in the holder OK but when I tried to remove them, they caught on the seal. I was able to slide a piece of film in between the slide and the seal to remove them.
Has anyone else tried this or how do you get more than 1 exposure on a piece of film?

Yes, I did it by sandwiching the film with a Stouffer step tsblet and exposed the film under the enlargerfor unsh.I used a LF lens with a shutter as the enlarger lens;needsan adapter to hold the LF lens but works well.

shutterfinger · Sep 10, 2014

A 1941 Kodak Commercial View, I had, has black glass sliders like E von describes for his Deardorff. They had a leaf spring on one side holding them tight in the frame slots. They fit in slots just in front of the film plane on the lens side of the back.
A mask that fits into the film opening in front of the film plane opening so that it does not affect the film holder or ground glass position should be easy to make and switch about.
If your camera has a fixed, spring back then a fask that fits onto the film holder in front of the darkslide should easy to make and use also.

peter k. · Sep 10, 2014

...A mask that fits into the film opening in front of the film plane opening so that it does not affect the film holder or ground glass position should be easy to make and switch about.

Ah like on a speed... on the ground glass, and the method of attaching the mask?

shutterfinger · Sep 11, 2014

Engineering fee $$$$.
How about pressure fit that just fits into the opening from thin, rigid material painted flat black.

peter k. · Sep 11, 2014

Engineering fee $$$$.

Oh ... Love it...

How about pressure fit that just fits into the opening from thin, rigid material painted flat black.

This would make the result an inside jest, for on a Speed, (I have no other LF to compare with) it would be an engineering feat, as I see it, so the mask wouldn't spring into the interior bellows area with the movement and flexing of of the film holder in and out, let alone of the dark slide itself. :munch:
Next... ?
Perhaps both our concepts are wrong... an can't help it I'm rolling on the floor with laughter...
Love these old large formats and the creativity you can get into...

Neil Poulsen · Sep 13, 2014

At the suggestion of Stu Levy, a Pacific N.W. photographer, I built a target that has 12, 2.5" openings. (3 rows of 4.) Each one has its own set of 3" filters. By illuminating it from behind, I can achieve 12 different test exposures on a single sheet of film. Of course, light behind the target goes through two translucent (blurry) sheets to even it out.

I experimented by using filters for 12 different stops. Didn't work; the lowest zones are too affected by ambient light. But, Zones 3, 6, 7, 8, 9, 10 work out just fine. (Using only 6 of the 12 test exposures.) Next time, I can add half zones. Note that I pivot on Zone 8, so, N+2 is 6 expanded to an 8, and N-2 is 10 contracted to an 8.

Darkslide Modification for Film Testing

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