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DrPablo
10-Jul-2006, 19:11
I've been trying to take some cityscapes with my 90mm f/5.6 Super Angulon and my 210mm f/5.6 APO Symmar. I seem to be getting a lot of strange distortion near the edge of the image with both lenses. I took a shot of one of the towers in Boston today and the straight vertical edge took a sharp turn towards the corner (this was with the 90), and something similar happened with the 210. It looks more like a pincushion effect than anything else. I don't have any scans to share.

Is this something that is the product of an intrinsic lens problem? I thought that distortion like this would be exceedingly unlikely with LF lenses.

Paul Fitzgerald
11-Jul-2006, 07:11
Hi there,

Not being funny but was the film installed in the holder correctly? Were either or both of the lenses dropped? They both have really fine reputations.

Just a thought.

DrPablo
11-Jul-2006, 07:17
I'm an LF newbie, so nothing should be taken for granted :)

I picked up a very lightly used kit, including these two lenses, from a studio photographer. He only used the camera and lenses for a few shots and only in the studio. So they've been pretty well cared for (and certainly haven't been dropped while in my custody).

As far as loading the film, I'm not sure how many ways there are to screw up putting a polaroid back in front of the ground glass as long as the emulsion is facing the right way, but if there are other ways to screw it up I'm sure I'll figure it out :)

Perhaps I should be very careful to ensure that the monorail is horizontal and I'm not dealing with perspective distortion that becomes more apparent at the edge of the frame.

Paul Fitzgerald
11-Jul-2006, 07:27
" a polaroid back in front of the ground glass "

Try it with regular holders and film to see if it is a problem with the camera. Sometimes a polaroid back does not press the film into place correctly, gremlins.

Good luck with it, it shouldn't be hard to find the problem.

Capocheny
11-Jul-2006, 13:03
Hi Doc,

And make sure the holder is properly seated in the camera back... you'd be surprised at how often this isn't the case! :)

Welcome to the club!

Cheers

DrPablo
11-Jul-2006, 14:23
Thanks for the feedback!

I'll take a look at some of my chromes when they get developed to see if it's still an issue.

JW Dewdney
11-Jul-2006, 15:39
The word 'distortion' could mean just about anything... take the way it's used in the audio world for instance. If you could better describe what you are seeing - then there's a MUCH higher likelihood that people can answer your question. A posted pic would be the best, though we understand if you have no means of doing so. The other possibility would be to find an image in google images that best resembles the symptoms of what you are seeing. To my mind what you are describing sounds highly improbable with ANY lens (except maybe a funhouse mirror) at best.

DrPablo
12-Jul-2006, 21:05
I don't have a scanner handy, but what I'm describing was a dramatic curve in some of the straight architectural lines, arcing from the center towards the corner and actually changing angle abruptly at one point.

Thankfully I've only seen this in Polaroids, but the transparencies I've gotten from the same shot have been free of this effect -- so it must just have to do with the polaroid holder or the film.

JW Dewdney
17-Jul-2006, 23:16
I don't have a scanner handy, but what I'm describing was a dramatic curve in some of the straight architectural lines, arcing from the center towards the corner and actually changing angle abruptly at one point.

Thankfully I've only seen this in Polaroids, but the transparencies I've gotten from the same shot have been free of this effect -- so it must just have to do with the polaroid holder or the film.

I totally get what's going on I think. SOMEHOW - you managed to push the polaroid too far into the holder and it probably popped out a bit or bent out of shape at the bottom (it WAS the top of the frame you said, wasn't it?). I would HAZARD a guess that you had some difficulty removing that one from the holder.

Michael Graves
18-Jul-2006, 19:27
I had to teach myself about inserting film holders properly into the back before I stopped getting otherwise inexplicable results. I also had to teach myself to pull the dark slide on the side of the film hold facing the lens and not the one facing the ground glass; but that the subject of a totally different thread.

paulr
19-Jul-2006, 11:37
lens distortion shows itself as subtle curvature of straight lines, not crazy bends ... so i'd bet JW is barking up a better tree with the polaroid issue.

Leonard Evens
19-Jul-2006, 13:32
I agree with the others. It is most likely the result of film position. Large format lenses typically have no noticeable distortion of the kind the you describe. If a lens were damaged enough to yield such distortion, it is hard to see how it couldn't have a whole host of other rather obvious problems. The fact that you see it with two lenses of quite different focal lengths supports the conclusion that the film is not flat. Also, since you don't say that you saw this "distortion" on the ground glass, can we presume that it appeared only on the film? If so, that would confirm that the film is the culprit.