Need help analyzing light leak

[stevenjo]

Hi guys,

I've been shooting with my Tachihara 4x5 and noticed some serious light leak in some photos.

I'm a newbie and I started 4x5 under the assumption that the dark cloth need not be attached most of the time. I could be very wrong.

So here's a sample photo no.1
Sheltered building but a lot of sunset light coming in.

No. 2
Model under shade but super bright sunlight at the back


No. 3
No bright light at all. Post sunset in a sheltered building
Looks completely fine to me.


I'm under the impression that there are light leaks at the film back - holder insertion point.

All photos are taken without dark cloth.
I tried putting a light source through the bellows but no leak.
When it is directed towards the film back - holder area, there are super faint light leaking. It's really a snug fit and the camera is in pristine condition.

Would love to hear what you guys think.

 

[Newt_on_Swings]

Maybe check the springs on the back, they need to hold the film holders tight to the back. Also another area where light can leak in is where the rear of the bellows meets the rear standard/back and clips in. My wista has such a problem and I have where I need to shield the back a bit. I'm looking for a perm fix too. Also maybe check your film holders, sometimes the felt gets old, and if you take the whole dark slide out there may be leaks too.

 

[adelorenzo]

My guess would also be problems between the back and the holder. Also if your camera has a removable back check that as well, I have had leaks in that area before.

Good article here:

http://www.largeformatphotography.info/leaks.html

 

[stevenjo]

leak

My guess would also be problems between the back and the holder. Also if your camera has a removable back check that as well, I have had leaks in that area before.

Good article here:

http://www.largeformatphotography.info/leaks.html

Thanks, what did you do to fix the leak?

 

[shutterfinger]

I tried putting a light source through the bellows but no leak.
When it is directed towards the film back - holder area, there are super faint light leaking.

Well you know where the leak is but not the cause.
1. The focus panel should put 5 to 15 pounds of pressure against the film holder when the film holder is in place on the back of the camera.
2. Check the grove in the back that the inner ridge of the film holder fits into. Remove any debris especially dust accumulated in the corners. Verify that the film holder sits flush to the back at the insertion end of the back.
3. Check the end of the film holder/focus panel opening for debris especially the corners. Verify that the film holder seats fully into the opening and sits flat against the the camera back when installed on the camera.
4. Check the velvet around the film plane opening, replace if worn. Felt can be used but heavy weight velvet is better in this area.
A 1/8 inch wide velvet strip can be put along the bellows frame to back or front standard to ensure light tightness. If felt is used it will need to be 1/16 inch thick and 1/8-3/32 wide.

To remove the focus panel on a spring back hold the spring down next to the spring to back retaining screw(s), remove the screw, then release the spring slowly. Lift the focus panel from the back once the screws have been removed.

 

[Light Guru]

The big light leak is in the bottom right of both images therefore you should check the top left of the back of the camera. See if it is holding the film holder tight.

 

[stevenjo]

Dark slide

As a matter of course, I've always pulled a little fold of the dark cloth back over the camera back as fast as possible after slipping out the slide. Especially important with the vertical usage of the film back, where the gaping darkslide slot points up at the sky. I can't imagine not doing this. That darkslide can spend quite a bit of time out of its holder when you are set for exposure and waiting for a lull in the breeze for leaves and grass to hold still.

Thanks, I think dark cloth is a must too now.

 

[Doremus Scudder]

I'm betting that there is nothing wrong with your camera at all and that you are simply pulling the back away from the camera when you are removing/inserting the darkslide. It's a common mistake and has exactly the look of you light-struck images.

I always pinch the back against the camera body between the thumb and fingers of my left hand when pulling/inserting the darkslide to prevent this.

If this is not your problem, start looking for a light leak between camera back and body at the upper left. Make sure the holder is seating properly and that there are no obstructions holding the back open.

I don't think it is you holders, since the first image you post has a clear black border around it. If it were the light trap, this would not be there. Do, however, check the light traps on your holders by shining a flashlight through them from both sides in a darkened room. Holders can sometimes be repaired, or light traps can be rejuvenated by simply soaking in soapy water for a while, rinsing and then drying thoroughly.

Leaky holders can still be used if you leave your darkcloth in place when the darkslide is pulled, raising it just enough to remove/insert. Many do this as a matter of course (me too when there is a lot of bright sunlight or I have to leave the darkslide out for longer periods).

Be careful replacing velvet/felt if you feel you need to. Replace only, don't add anything (many cameras are designed to work without it) and be sure not to add more thickness than originally intended or you can end up with worse problems including focus shifts.

Best of luck,

Doremus

 

[John Koehrer]

Like several have mentioned, check that the holder is correctly inserted and tight against the camera back. The darkcloth won't hurt but if you don't like to use one, just put a flap of opaque fabric (width of camera X 100mm) over the top of the GG frame & holder & flip it over the area when you put the holder in. You can try the flap idea by taping the fabric in place.

 

[pgomena]

You did try the flashlight trick, but do it again with a film holder in place. If you see light leaking out around the top edge of the film holder, you'll know if it's a problem.

If you have old film holders, particularly if they are wooden, they could be warped. This is not common, but leaving a plastic film holder in a hot car on a sunny day can do very bad things.