Best practices for testing light leaks in new film holder - 12x20

I got a new (to me) 12x20 holder for my Folmer Schwing 12x20. It is not a Folmer Schwing film holder. I shaved down the ridge on one side to test it out.

I need to isolate some other issues with the camera to fully test the light-tightness of the holder. I am curious what best practices are with testing a new-to-you film holder.

I have some 10x12 xray film. I was thinking of loading some up and just letting the holders sit out in the sun for a bit. Then developing them to look for any leaks. This film is cheap so not a big deal. just time spent.

Thoughts?

If you have photo paper, you could use that.

Another potential leak area is the light trap when slide is out of holder...

Take a small bright flashlight and holder in dark room, pull slide out, and shine light from inside holder while you look at slot where slide enters... Move light around and look carefully if you see and faint ridges of light in slot, esp the corners (that tend to wear most)...

Steve K

I suggest buy X-Ray while we can


14x36 in. Full Length Fuji X-Ray Film - Green HR-U is being dumped by ZZ Medical who sell FRESH film, unlike eBay

Cut it down and test with it, ASA 40-80

then shoot some too

The main place a holder will leak is at the area where the dark slide is inserted. The brass spring stock may be deformed or the black fabric is missing. This is easy is find by removing the dark slide and looking into the area where the dark slide goes if you see light there is a problem. This is repairable.

Other areas of leakage would be the side rails are warped. This can be found by looking along the length of the side rail or using a straight flat metal 12 inch carpenter square rule set on the face and look to see if it lays flat with no gaps. If there is a gap the holder will leak light if you do not keep the focusing cloth over the back of the camera. This is not repairable. This is one of the most common problem with older holder that were not stored right.

Many years ago acquired an 14x17 camera with 2 holders. The holders proved to be light tight by loading them with sheets of graphic arts film and leaving them in the sun for a few hours. When I started to use the camera though, I got all kinds of light leaks on the film. Amazingly the back was not warped, as this was my first thought. I finally realized that the 4 metal back tensioners suffered from serious metal fatigue, and I had to replace them. They held the film holder in place, but not tight enough when removing or replacing the dark slides.

Thanks for all the replies. I will try these out.

Regarding X-ray film: When will it go away? I assume this is due to the change over to digital?