Identifying light leak

[Jiri Vasina]

Hello all,

I'm trying to improve (or get functional) my LF camera - my Ica Ideal 325 to which I built a reduction back to use ANSI standard holders. I have shot several sheers of film, and on almost all (90%) of them there is a light leak as shown on the attached scan.

I can not identify the source of the leak. I tried the bellows and it seems to be light tight. I can neither find the source anywhere else.

Could someone please lead me to the possible source?

Thanks a lot

Jiri

[Scott Davis]

Looks like a film holder issue- either the holder itself has a leak, or the back isn't holding the film holder tight enough in spots.

[Kirk Gittings]

It looks to me, as Scott suggested, that it is a back problem. Either the film holder was not inserted correctly or the back doesn't hold it flat. I say this because the light seems to be intering from the side of the holder casting a shadow from that little loading indentation above the film.

[Jiri Vasina]

OK, thanks for the suggestions. I think it will be because of the back (I constructed it :( ) and the holders would be OK, as the issue is same in several different holders...

So I'll check the back. Maybe even redesign...

Jiri

[Ernest Purdum]

Jiri, Is there a groove in your back to take the ridge on the holder to lock the holder in place?

[al olson]

Usually the camera back has a felt material that presses against the sides of the holder. It appears to me that this is where the light is getting to the film. The problem could be that the material is uneven, or worn, or maybe nonexistent.

You can always use the old flashlight test ... again. Put a holder on the back, remove the lensboard and shine a flashlight inside. You should see some light coming out from around the holder that will identify your problem.

Also remove the darkslide to check if the light trap is leaking. If your holders are old they could all be leaking at the light trap.

[Andrew O'Neill]

If you constructed the reducing back yourself, I would suspect that your holders are not sitting flat.

[Jiri Vasina]

Thank you all for your suggestions. I'll try them on the weekend (weekdays it's just too late in the evening when I come back from work).

Yes, when designing the back I knew there has to be a groove functioning as a light trap. I made several ridges there that fit like two "E"'s one in another. But obviously it is not enough. I think the holder should be held flat against the back, I have rather strong springs holding the filmholder in the back. Also, I painted the whole back in black matte paint (that goes well with the black leather of Ica Ideal).

[Jiri Vasina]

Thanks for the tip using white paper in the holder to check for the leak. It worked. I found a hole through which light could get in (it was my faulty design of the camera-back). I now think I fixed it, but have to develop some film to try it out...

Jiri

[CP Goerz]

As a quick fix try putting a layer of black velvet against the part of the back where the film holder is pressed against when inserted, the T distance isn't affected as the groundglass is moved the same distance away from where the film will finally sit.