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Nico
Tinkerer
Username: Nico
Post Number: 36
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 04, 2010 - 09:52 am: | 
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Hi everyone
I've recently repaired a Canon Demi S that really was cancer, having so many problems to fight with, but after many days and hours of efforts I managed to make it work amazingly well.
What I've noticed here, while printing some negatives from a test roll, is that the frames have very pronounced rounded edges, and out of focus either. I was wondering about the cause of this problem but wanted to comment it before with you guys, to see if any of you had that symptom too on any camera. I think it could be a weak pressure plate but I haven't any way to prove it.
Anyway, I'll upload too samples images bellow so you can judge.
They are ugly photos but as I said its only a test roll (some scratches too :D )
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Jpartsch
Tinkerer
Username: Jpartsch
Post Number: 13
Registered: 12-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 01:58 pm: |
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It looks like you may have installed one of the lens elements backwards. A weak pressure plate can usually be easily solved by a little gentle bending to get it to sit a little further above the back door of the camera. I hope this helps. |
Nico
Tinkerer
Username: Nico
Post Number: 37
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 05:48 pm: |
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Thanks J, I'll try doing the bending when I get back home. But, really? It could be possible to assembly the whole lens with one putted backwards? How can you tell that?
Oh and I forgot to say that another problem with the negatives is the separation between them, which is very irregular and, in some cases, can make one frame go over another. But I assume that is another symptom regarding some malfunction of the film advance mech.
Also, I want to clarify that the Newton's rings that appears in the upper section of the second image are caused by the enlarger, not the camera. Just in case...
Best regards! |
Greyscale
Tinkerer
Username: Greyscale
Post Number: 21
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 07:07 pm: |
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Nico, I have followed your adventures with the Demi over the past several months, and I would like to say congratulations on getting the camera back in working order. Considering the shape the lens was in, I think that your "ugly test photos" are actually quite remarkable. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1113
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 07:27 pm: |
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I would suspect the film not lying flat in the focal plane. A misassembled lens would make the image bad (probably vastly worse than these) but it should not affect the shape of the edges of the frame. Also, while it is easy to get the center element of a triplet in backwards, a complex lens like the one on the Demi S is less likely to allow this sort of thing to happen and still get it back together. |
Nico
Tinkerer
Username: Nico
Post Number: 38
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 09:37 pm: |
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Thanks Greyscale! You are right, considering the shape of the lens, even I was absolutely surprised and obviously very pleased and happy.
All that work wasn't for nothing and now I'm amazed with the practicality and quality of this little camera that allows me to be much more free on my photographic work. I didn't post the result on the other threads so I will. Here is another photo taken with it. http://www.flickr.com/photos/_nomen_nescio/5117759039/
This time "more intentional" with an orange 34mm filter I've found :D
Rick, I thought the same, it is a very idiot-proof lens assembly. I think you are right about the film and focal plane, tomorrow I'll try that hint Jpartsch mentioned above. |
Greyscale
Tinkerer
Username: Greyscale
Post Number: 22
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 05, 2010 - 10:23 pm: |
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That's a nice shot, Nico. But I think that Rick and the others are right about the film not lying flat.It also looks like you are getting horizontal scratches on the negative? It may be that the pressure plate is to tight against the top of the film (bottom of the image), causing a bind (and the scratches) at the top, and allowing the bottom to flex or skew, causing the distortion in the image. |
