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rguinter
11-Jan-2010, 18:54
Greetings everyone:

I've recently began shooting infrared in 4x5. I've read some other posts where I was warned about infrared light leakage at various points in the process that can damage the negatives. So I've been as careful as possible to try and avoid this.

But I am continuing to see a thumb-size area of infrared bleed-through at the corner corresponding to the upper right of the film holder.

So obviously the light leakage is through the top of the slot for the darkside.

Makes sense with the sun above.

Just wondering if anyone has some thoughts about ways to deal with this. I was thinking perhaps to cover this area with aluminum foil while the exposure is being made or perhaps covering the back standard with my dark cloth. But my exposures are in the 30-sec to 2-min range and in the breeze these things would probably add to camera shake.

So others thoughts and suggestions would be greatly appreciated. Best regards,

Bob G.

vinny
11-Jan-2010, 19:26
I have several holders that do this. In the proper light, pull the slide, open the flap and line up the corner of the holder you think leaks with your eye and the light source. Chances are, you'll see a small hole. Don't use that holder.

vinny
11-Jan-2010, 19:27
I have several holders that do this. In the proper light, pull the slide, open the flap and line up the corner of the holder you think leaks with your eye and the light source. Chances are, you'll see a small hole. It's not easy to see though. Don't use that holder.

JRFrench
11-Jan-2010, 19:41
I pulled apart a film holder the other day, and the light seal in the darkslide was a strip of thin brass with felt glued to it, Im fairly sure this brass didn't go all the way across the slot, with gaps at the end where the felt did the work. Perhaps a gap like this is the one causing your IR leaks. Perhaps you could make a little swinging plate out of brass or similar that swung over the dark slide slot when the slide was removed? It could be a very simple strip with bent ends, attached by two very small screws. A model store would have suitable brass strip. This would be easier if your holders were wooden.

rguinter
11-Jan-2010, 20:10
I have several holders that do this. In the proper light, pull the slide, open the flap and line up the corner of the holder you think leaks with your eye and the light source. Chances are, you'll see a small hole. It's not easy to see though. Don't use that holder.

Thanks for the tip Vinny. I've been using my best Fidelity holders for the infrared but perhaps they are not the most light-tight at that corner. I'll check it out using your method. Bob G.

Nathan Potter
11-Jan-2010, 20:12
My thought - if your thumb is warm it is emitting IR radiation which could go through the darkslide and fog your film? :D :D

Nate Potter, Austin TX.

rguinter
12-Jan-2010, 03:52
My thought - if your thumb is warm it is emitting IR radiation which could go through the darkslide and fog your film? :D :D

Nate Potter, Austin TX.

Nate:

At first I thought it might be an actual thumb print while I was handling the film but I dismissed this thought right away. My technique for loading and unloading film causes me to touch the film at the edges but not at that spot.

I just used the thumb-size as a description of how large the bleed-through damage seems to be. Bob G.

Wallace_Billingham
12-Jan-2010, 07:40
Something as simple as black masking or gaffers tape will block the IR light. I would remove the darkslide with one hand and use the other to shade the spot where the light leak is, then put a piece of tape of the spot, make the shot and reverse the process

rguinter
12-Jan-2010, 11:13
Something as simple as black masking or gaffers tape will block the IR light. I would remove the darkslide with one hand and use the other to shade the spot where the light leak is, then put a piece of tape of the spot, make the shot and reverse the process

Wallace:

Sounds like a plan and thanks for the tip. I should've thought of that right away. Similar to my idea of aluminum foil but it would probably stick better in the breeze.

Now to find my old roll of black gaffer's tape. Haven't had much need for it in a number of years since (semi-) retiring my old Oribit rail camera that has been in the closet since getting my Tachihara.

Cheers,

Bob G.

rguinter
17-Jan-2010, 11:54
Another possible solution... I'll call it the hat-trick. I went out yesterday with my infrared film and alas I forgot to take the gaffer tape with me as I was advised above. I just knew I was going to do that. So instead I clipped my black cap to the carry handle of my Tachihara with a clothespin which I had in my parts bag. I let the cap drape over the slot of the film holder after pulling the darkslide. Film not yet developed but I sense this technique holds some promise. Bob G.

michael sage
17-Jan-2010, 14:52
I use to see this a lot until I kept my focusing cloth over the holder during exposure. They disappeared when I started doing that.