Puzzling light blocking. Vignetting, lens hood? Please help to identify the source.

[Vic Montaigne]

Hello to everyone!

In a series of shots taken last year all came out just fine except for four consecutive shots, 2 identical exposures for each of 2 images. They show a broad stripe of blocked light (white in the negative, black in the print), 3 of the stripes being pitch-black across the top (of upright image), the first stripe however of similar width, but on the bottom end and not completely black but somehow like horizontally pleated.

I am not absolutely certain I can rule out a developing issue. But I think so, as these four negatives were developed in a batch of six in a MOD54 tank, the other 2 negatives being fine. All four shots were taken with a Schneider SA 5,6/90 and lots of rise (first image and backup 44 mm, second image and backup 46 mm). The lens allows for 47 mm in portrait mode, so that was quite close to the limit. F-stops were 33 2/3 in the first two shots, 22 1/2 in the two following shots.

I cannot swear if I had the Lee Wide Angle Lens Hood mounted, but I think I did so routinely, mounted with a wide angle adapter ring.

So, what possible mistakes would be capable of producing such phenomena?

If it was lens vignetting, caused by exceeding the image circle, shouldn't there be some round corner vignetting instead of a stripe? Also, I tried the same setup at home under well-lit conditions. Checking through the GG corners, I could not find any signs of vignetting at the apertures used. (Without rise no vignetting from f 11, with rise of 44-46 mm no vignetting from f 22.)

Second possibility, would a black stripe be consistent with blockage by the lens hood, wrongly adjusted? While checking the corners the Lee Wide Angle Lens Hood shows up only when fully extended (which I can rule out) or when in oblique position. The latter would have been possible. If I was in a hurry, e.g. because of fast approaching dark rain clouds, I might have inadvertently touched and turned the hood after having checked for vignetting. Or I might have had difficulties in checking due to light conditions.

I would love to pin down the cause. If I have simply exceeded the movement possible with this lens I would consider exchanging it for a SA 90 XL, although this would pose other problems with the TK 45s I used. At the occasion the four shots were the only ones I made with the SA 5,6/90. For all others I used the 72 XL, 110 XL, 150 and 240 lenses. This might be coincidence, but then it might not.

Image circle, lens hood or something else, what can cause broad black stripes?

Thanks,

[djdister]

You really need to post some photos or scans of the problem.

[ic-racer]

Shadows from bellows, lens hoods, filters etc, that can spoil a negative need to be observed on the ground glass at working aperture. Maybe you need a better dark cloth?

[Bob Salomon]

Are you using Riteway holders?

[Vic Montaigne]

Bob, thanks for responding. No Riteway holders are involved, mine are all Fidelity Elite holders. After exposure I pull out the dark sheet completely, turn it to mark exposure and then reinsert it.

(If I may I would like to ask you a question concerning the SA 90 XL mentioned in my post as a possible alternative for the SA 5,6/90. It is from one of your posts that I learned that the SA 90 XL will not pass the opening of the TK 45s' front standard. Will the version with removable rear flange pass? According to Schneider specs the diamater is 86 mm with flange, 78 mm without. I measured some 83 mm for the TK opening. So it should be a tight fit but possible. Would you know for sure from experience if it will fit with the rear flange removed?)

[Bob Salomon]

Bob, thanks for responding. No Riteway holders are involved, mine are all Fidelity Elite holders. After exposure I pull out the dark sheet completely, turn it to mark exposure and then reinsert it.

(If I may I would like to ask you a question concerning the SA 90 XL mentioned in my post as a possible alternative for the SA 5,6/90. It is from one of your posts that I learned that the SA 90 XL will not pass the opening of the TK 45s' front standard. Will the version with removable rear flange pass? According to Schneider specs the diamater is 86 mm with flange, 78 mm without. I measured some 83 mm for the TK opening. So it should be a tight fit but possible. Would you know for sure from experience if it will fit with the rear flange removed?)

Yes, that version will work. It is the reason why Schneider had to redesign the rear group.

Many of the later holders made by Fidelity/Lisco did not seat properly in the Linhof back and would feel like they were fully seated when, in fact, they were about ½ an inch from seating fully. This created a strip like you are describing. After a dozen or so insertation and removals this problem disappeared.
It could also be eliminated by lightly running a file over the sharp ridges in the light trap area of the holder. Could this be your problem? It was pretty common when Fidelity was still in business making holders but has not been very common over the past decade or so. It was so bad at one point that I had to visit their offices in CA to see what was going on and how to solve it. Apparently their older molds for the holders were worn out and they re-tooled without checking Linhof's specs. But since they were part of the group that owned Cambodia maybe they didn't worry about brands with tighter specs.

[Vic Montaigne]

Thank you for this valuable hint. I take it that the "light trap area of the holder" is the area at the bottom end when inserted. Please correct me, if I got you wrong. I have just identified and inspected the two holders in question and could not find anything that caught the eye. One of the holders has been used before without problems.

However, you are right in that it IS a very tight fit. In general I tend to use force cautiously, accordingly I find it quite conceivable that at some point I happened to stop short of complete insertion without noticing. The fit is really tight and the spring of the back very strong. Be assured, from now on I will take special care to thoroughly insert the holders. Thanks again for reporting the story!

Case solved I hope. However, should anyone be aware of other possible causes for a broad black strip on top (bottom in camera) please let me know.

[Bob Salomon]

Thank you for this valuable hint. I take it that the "light trap area of the holder" is the area at the bottom end when inserted. Please correct me, if I got you wrong. I have just identified and inspected the two holders in question and could not find anything that caught the eye. One of the holders has been used before without problems.

However, you are right in that it IS a very tight fit. In general I tend to use force cautiously, accordingly I find it quite conceivable that at some point I happened to stop short of complete insertion without noticing. The fit is really tight and the spring of the back very strong. Be assured, from now on I will take special care to thoroughly insert the holders. Thanks again for reporting the story!

Case solved I hope. However, should anyone be aware of other possible causes for a broad black strip on top (bottom in camera) please let me know.

Just rub those sharp edges of the holders with a file or sandpaper to round the edges off a bit and that will solve the problem.

[Michael W]

What camera?

[Vic Montaigne]

@Bob

Just rub those sharp edges of the holders with a file or sandpaper to round the edges off a bit and that will solve the problem.

I will check the whole bunch and smoothen the edges where appropriate. Thanks for pointing out.

@Michael W

What camera?

As mentioned before the shots were taken with a Linhof Technikardan 45s (abbr. TK 45s).


EDIT of my post #5: I of course do not pull the dark slide after exposure but before. Otherwise images would show even more light blocking...