Lens flare? Bright corners

[Antti Aalto]

Hi,
I've got a problem with bright corners on negatives and I'd like to find out what's causing it. I'm pretty sure, but not absolutely certain that there should've been no direct sunlight falling on the lens taking any of these pictures, and especially the third one I clearly recall the sun being behind the camera. Here are links to the pictures.
Picture 1 (http://kotisivu.dnainternet.net/turska22/IMG_0955.JPG)
Picture 2 (http://kotisivu.dnainternet.net/turska22/IMG_0957.JPG)
Picture 3 (http://kotisivu.dnainternet.net/turska22/IMG_0952.JPG)
I actually took two nearly identical pictures like the third one, the second with filtration, and both show the same pattern or bright corners, the top right corner being especially bright. Also the whole right edge in #1 and #2 is clearly brighter. I'd like to know whether this is just bad shading or something else. If it should likely be bad shading, the lens has to be real picky.
It's a Schneider-Kreuznach Tele-Xenar 1:5,5 270mm objective with a compur shutter. I checked the lens serial on the manufacturer's website and it's from the '50s and has a red triangle on it, which I was told means coated lenses. With all of the images above, unlike with vignetting, I couldn't see the effect on ground glass, but maybe I just wasn't looking carefully enough. The deal I've got with the very kind guy I purchased two objectives from was that he knew one of the six I chose from had some kind of problem, but he couldn't recall which it was and could it be fixed. So can this lens be fixed and for about how much? The deal went that I'd be able to change the objectives for the others he had, if there were problems. I'd be able to change this for a Tele-Xenar 5,5/360mm for little extra cost.Thanks a bunch for all answers!

[Dan Fromm]

Um, er, ah, a negative with lighter corners than center received less exposure in the corners than in the center. That's vignetting, not flare, the lens doesn't cover the format.

[Antti Aalto]

:) That's why I included the pictures. Forgot to mention they're taken of negatives though. They're denser at the corners, so brighter as in more light passed onto the negative near edges.

[Graham Patterson]

Looks like light leak in the camera. Either a problem with a detachable bellows, or light leak around the lens or lens board. Doesn't look like film holder fogging or fogging in the box.

[paulr]

does this problem only happen with that one lens? it doesn't look like flare to me.

[Bruce Watson]

I'm with Graham. Looks like light leaks around where the bellows attaches to the rear standard.

[Kevin Crisp]

This doesn't look at all like lens flare to me. In some of these it doesn't even look like you were exposing in direct sun. I think Bruce and Graham have given good suggestions for where to look first. Also, if they're right, that would explain why you don't see the issue on the ground glass, especially if you are covering the problem with the dark cloth when composing. Even a very dim leak (which you couldn't see when composing) can expose the film over the time the dark slide is removed. Put a new sheet of film in the camera in the sun with this lens on it, pull the slide so that the film is open to the supposedly dark inside of the camera for a minute or two, DON'T TAKE A PICTURE, develop it and see if you get density. My hunch is you will. That would eliminate lens flair. Try the same thing with a different lens on a different lens board. If it doesn't happen that time, look at lens board fit, possible pin holes, etc. that are peculiar to this lens and board.

[Antti Aalto]

I just checked and I can't see a leak, and yet the leaks should be quite apparent since the negative's in place without a darkslide only so long and gets exposed around the edges like that right? It's a tele objective, and the three pictures above have been shot focuse almost at infinity, which means the bellows are less extended than they are in the position you fold the camera in. The camera's new and I checked it for light leaks when I got it and just now, though with a poorer test setup - nothing. I checked with the lens attached and there's no light coming through at the lensboard that I could see. Could this be due to a film holder put in poorly? I tried with a holder and at least this one didn't leak when viewed through the front standard, so maybe I've just put them in poorly? How likely is that, if you suppose you take some care doing it?
Here're three pictures I've taken with the other objective I've got, a 90mm Angulon. At infinity the bellows are quite compressed, so you wouldn't necessarily see the leak, but these three were taken close to the subject, bellows almost fully extended. You'd suppose if there was a light leak near the rear standard, it would be very evident here, right? The first of these (no.4) has a clearly similar effect with the first three, but on the latter two I would disagree, as the digital camera I took the pictures with has some fall off around the edges too, and if you compare these to the first three, the pattern in the first three is rather particular (especially the top right corner of the negatives).picture 4 (http://kotisivu.dnainternet.net/turska22/IMG_0958.JPG)&nbsp&nbsppicture 5 (http://kotisivu.dnainternet.net/turska22/IMG_0959.JPG)&nbsp&nbsppicture 6 (http://kotisivu.dnainternet.net/turska22/IMG_0960.JPG)
Especially taking the particular pattern of the leaks or whatever they are into account, you'd think this has to do with the particular objective/lensboard, right? The first three pictures were taken with the lens fully stopped down (f/32) if that may count for anything.

[Antti Aalto]

Problem found, thanks for the suggestions, I'm not sure if I would've found it without them.
It's indeed a light leak at the lensboard . I didn't know it would be that elusive; I actually had to let my eyes adapt a while to see that it leaks very slightly basically aroung the whole shutter. The next thing is I need to figure out how to fix it. Generally, can you just mount the lens better on the same lensboard, or does it take a more snug fit lensboard to fix these leaks?

[Donald Hutton]

Check to see that your lens does not have one of those little grub screws for preventing twisting of the shutter on the board. If it does, remove the screw, tighten up the retaining ring and you should be all set.

[Graham Patterson]

I have seen lenses mounted in boards with too large a hole - #0 shutters in #1 holes - but I don't think this applies in your case. If it does, a ring of black paper on the inside of the lensboard might be all you need.

[Antti Aalto]

I checked the other objective as well, and the effect's less pronounced but it leaks too. I guess this is what you get when you buy things from someone who mostly collects them instead of putting them to use. Anyway, are washers generally used to provide better fit? The tele objective hasn't got a washer, it's just plain tightened up with the ring, which I've tightened with pliers as much as is reasonable, and it still leaks. There're no notches nor screws and since it leaks all-round, well, should that indicate the shutter's not bent or the other way around? The 90mm angulon's got a couple of cardboard washers to seal it better, but it leaks too. To repeat, are washers normally used, if yes, then washers of which material? Cardboard, copper, silicone? What other tricks should I try to seal the leaks? That is, if I had them fixed by a professional, what would that person do? Or do they just need new lensboards? I wouldn't be that cheap to have them fixed and I suppose if I can't do it myself with reasonable effort, it'll be worth my while to go talk to the seller and check if he's got objectives that don't have leaks and try to have mine exchanged for those. I recall he had a 90mm Congo he considered better than the one I bought, so I might go for that. Anyway, I'm glad the leak wasn't in the camera, as it's already long since declared and I'd lose quite a bit of money if I had to send it back to Adorama to be repaired.
Thanks!

[Kevin Crisp]

Well, if the hole is just plain bigger than it needs to be that's a problem. I am sure many on the forum have made do with that arrangement, even though it is not ideal. You might cut a washer out of cork, this works quite well since it compresses and lasts a long time, sheets of this are sold at auto parts stores as DIY gasket kits. But yes, they need to be reasonably tight. To seal out light and so you don't get annoyed when the lens starts turning around in the middle of a day out shooting somewhere. Does this lens have a slim ring or a wide flange or something else? The answer to your question is normally washers aren't needed, the hole is just big enough and the lens board isn't too thin so the retaining ring snugs it up light tight. If you are using a flange which should be front mounted with screws to the board, and putting it on the back instead. it may be more prone to leaking.

[jaime arroyo]

I have used a thin felt product sold at hardware stores as drawer linning. It is self adhesive and very thin. It provides a light tight seal and also provides a very good contact surface for the lens to mate to the lens board. This felt comes as a sheet about 10 x 10 inches, cut a strip and form it around the mating surface on the back of the lens. It comes in green and also in dark brown, I use the brown. Good luck.

[Jon Wilson]

I concur with using black felt. I have also found that plastic/rubber plumbing washers slipped over the rear shutter's threading can make for a light 'N tight fit with a flange.

[Brian Ellis]

If the lens board hole is just too big for your shutter the solution is to buy/make a board with the proper size hole (or buy an undrilled board and drill the proper size). "Fixing" the problem with felt or a washer or something of that nature is IMHO a mistake. You'll never know that the washer or the felt moved or deteriorated or something else happened that caused the light leak to return until you start developing your negatives after a week long trip for which you spent thousands of dollars or after getting what you think was the shot of your life and see that none of your negatives are printable. You can make a lens board yourself for only a few dollars, you can buy them on ebay used for just a little more, you can buy them new for $30 or $40 or you can have one custom made by S.K. Grimes for $50 or so if you want to go first class.

[Antti Aalto]

Just an update for no particular reason.
After talking to the seller of the objectives and having him provide a powerful movie projector as a light source we confirmed that the light leaks are caused by a bad front standard on my Tachihara. Both lensboards fit a Linhof Technica IV with no leaks and they seem to fit my camera as well, but the fit is not light tight. Maybe the wood's warped, I don't know. I'll have to sort this out with the camera retailer.
OT:This doesn't go with this topic at all, but since the forum can be searched and it's not worth its own thread I'll post this here. I purchased a Tamrac Expedition 8 backpack (5578). I've still to see if the manufacturer will fix the backpack for me, so I'm not trying to defame them, just informing. Loaded with my LF gear, meaning it could still be much heavier, once adjusted and tightened, the top and front adjustments for the harness will loosen up rapidly and make the 5578 a poor backpack. Rapidly means you need to be pulling the straps tighter every 10-15 minutes and the backpack won't hold its place at your waist either because of this. Otherwise I like the backpack, when it fits it feels good. If you're trying such a pack out, make sure yours won't loosen up when you walk with it loaded. They may've used different materials for different batches of the bags, who knows.