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120 / 220 film RF's 120 / 220 format rangefinders including Fuji, Koni-Omega, Mamiya Press, Linhof 6x7/6x9 cameras, Mamiya 6/7 among others, but excluding the 120 folders and the Voigtlander 667 cameras that have their own forums.

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Mamiya 7 Distortion & Winding Issues
Old 01-14-2019   #1
bendickey
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Mamiya 7 Distortion & Winding Issues

I'm pretty recent to the Mam 7 lineup, but have been really enjoying it thus far. However, I have noticed a clear bit of fall-off and barrel distortion in many of my compositions. From what I've heard the system is supposed to be very good with both of these things, but most of my images have to be perspective corrected in post and many still contain irritating dark corners. Has anyone else notice/struggled with this? Could there be an issue with my setup, or lens?

At this point I've probably run 30+ rolls through it, and until yesterday have had no problem with the winding mechanism, or loading. I loaded a roll with no indication of an issue or looseness, yet when it came to the last two shots, the winding became stiff, and I heard the dreaded sounds of a roll getting caught. In the end it had come loose to the point, when I took it out it was too loose from the spool and would definitely have let light in had I not stuffed it in black bag I had. Wondering if anyone has had issues with this on the Mam 7 before.

I've attached a couple of images with examples of the fall-off/distortion I'm referring to.

Thanks so much!
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File Type: jpg Win,Die,Lose copy.jpg (53.4 KB, 53 views)
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Old 01-14-2019   #2
Doug
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I see a bit of corner illumination fall-off. A mild case. First thought raises questions about use of a lens hood... If the hood isn't quite wide enough and intrudes a bit into the field of view, that would darken corners. But a bit of corner darkening is a natural optical consequence of lens design, often even a desirable one!

Holding a straight-edge along some assumed-to-be-straight lines in your pics, I cannot see any barrel distortion. Just a few tilted items, perhaps a bit of camera tilt in the first one. Any pincushion or barrel distortion would be most noticeable in straight lines near the frame edges. Off-straight lines nearer the center would not be the fault of the lens, just the nature of the subject.
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Old 01-15-2019   #3
Karlovak
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Hold your camera straight. If needed, use an elevated ground, like small ladder steps.

Load film with the take-up spool slit as close to the edge of the frame as possible, or you might lose the very end of last frame.

What's strange is the corner illumination in the first one, did you up the corners in post?
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Old 01-15-2019   #4
Karlovak
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What I use for my architectural photos, of high-rises etc, is a panorama stitcher like PTGui. Take two shots, one straight, one tilted up leaving 20% overlap and stitch them together.
PTGui does a very good job at retaining detail sharpness and fixing parallax, I don't need to use a panoramic tripod head. Crop for 4x5/6x7 ratio in post.
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Old 01-15-2019   #5
FujiLove
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I can't see any distortion either. The Mamiya 7 lenses are just about the best you can buy for medium format, so I doubt there's much distortion.

Hate to say this, but do you have a shot of a brick wall? :-)
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Old 01-15-2019   #6
ka7197
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Quote:
Originally Posted by bendickey View Post
I've attached a couple of images with examples of the fall-off/distortion I'm referring to.
In these pictures, I don't see the slightest bit of distortion and only a minuscule (and totally non-objectionable) amount of light fall-off in the corners.

A very low degree of light fall-off at full aperture is just normal. To avoid it, stop the lens down by one or two stops (i. e. to f/5.6 or f/8). Stop further down if you need more depth-of-field.

The barrel- or pincushion-shaped distortion of all the Mamiya 7 lenses is so low that your eyes won't notice unless you check straight lines near the frame's edges with a ruler. The distortion of converging lines, however, can become pretty obvious—this is not a fault of the lens but an inevitable consequence of tilting the camera and lens up or down. That's why there's a bubble level built into the accessory viewfinders of the wide-angle lenses.

Regarding the film-winding issue—I'd guess you just screwed up the loading of the film ... slightly. When the film doesn't sit firmly and perfectly straight on the take-up spool from the beginning then it might become more and more askew with every frame until a problem arises at or near the end of the roll. Just make sure to load the next roll very carefully.
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Old 01-15-2019   #7
Papercut
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Count me among the "What barrel distortion?" crowd. Have you had your eyes checked? More seriously, using ramshackle structures to judge distortion is probably not a good idea. (Exposed plywood? Even if it was straight coming out of the mill, a week in the weather would leave it wavier than cooked bacon.) The Mamiya 7 lenses are fantastic, so any bowing or sagging you may be detecting is almost certainly in the structures themselves and not from the lens.
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Old 01-15-2019   #8
kram
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What lens is it. There is naff all distortion with yhe Mamiya 7 lenses. The only fall off I noticed was with the 43mm. All the rest were fine for me with regard to light fall off at the edges.
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Old 01-15-2019   #9
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I just stumbled across some old lens test data, and the distortion diagrams show some small degree of pincushion-shaped distortion for the N 150 mm L and some equally small degree of barrel-shaped distortion for the N 80 mm L ... even though I never noticed any distortion in my photographs so far. The wide-angle lenses are virtually distortion-free, according to those diagrams.
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Old 01-17-2019   #10
bendickey
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Hey everybody! Thank you for the responses! I posted a reply here earlier, but I guess it didn't go through. It's the 65mm lens and for the most part I make an effort to hold the camera level, however I'm sure there are times when I tilt in order to get more subject in the frame. Perhaps I'm just getting stuck on details, but it really does feel as thought there is a convex quality to many of the images. The fall-off is probably not helping this appearance. That being said, perhaps my expectations were too high, but I still see a lot more fall-off than I'm accustomed to.

@FujiLove I think I might have to go out and snag a photo of a brick wall to double check.

@Karlovak I did nothing to the pictures in post except convert to jpeg. Thanks for pointing me to PTGui. Looks very cool!

@Doug No hood unfortunately.
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