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Nesster
Joined: 24 Apr 2008
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Location: NJ, USA
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 Posted: Wed Oct 15, 2008 12:30 am Post subject: Folding camera lens collimation?! |
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Nesster wrote:
Can anyone explain or link me to some place that explains the geometry of a triplet lens? What I'm after is this: what do I adjust to collimate (set the infinity focus) correctly?
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Last edited by Nesster on Wed Oct 15, 2008 1:15 pm; edited 1 time in total |
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Nesster
Joined: 24 Apr 2008
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| Posted: Wed Oct 15, 2008 1:15 pm Post subject: |
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Nesster wrote:
I should clarify: This is for a folding camera with front cell focus. I can't seem to get the front element back enough to get good infinity focus. I'm wondering about the two other elements, which direction to move them... for example, if I move the middle element out a tiny bit, will that help?
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Xpres
Joined: 11 Dec 2007
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| Posted: Wed Oct 15, 2008 1:54 pm Post subject: |
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Xpres wrote:
Was it working before you took it apart? And how are you checking infinity - ground glass & lupe?
Whenever I've put one of these back together I've never had to move the rear element from where it was - yet - but my feeling is it would need to be closer to the film plane. Is it a bellows camera or fixed?
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Nesster
Joined: 24 Apr 2008
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| Posted: Wed Oct 15, 2008 2:02 pm Post subject: |
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Nesster wrote:
Thanks, it's a Bessa I bellows, and never did get infinity but rather a couple of hundred yards. I arbitrarily unscrewed and re-screwed the front element, and 'checked' with film 
I'm going to setup a proper testing rig, but want to collect a bit of knowledge beyond the front element before I do so.
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peterqd
Joined: 28 Feb 2007
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| Posted: Wed Oct 15, 2008 2:28 pm Post subject: |
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peterqd wrote:
Could it be that the whole lens (and the front of the bellows) are being taken too far from the film when you open the camera? I don't think I'd want to adapt the lens before checking this aspect.
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Nesster
Joined: 24 Apr 2008
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| Posted: Wed Oct 15, 2008 2:41 pm Post subject: |
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Nesster wrote:
Good point, though everything seems in order there.
Apparently there are more than 1 starting points for the front element threading, I figure I'll try the different starting points to see which if any screw in the furthest.
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Sevo
Joined: 22 Aug 2008
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| Posted: Wed Oct 15, 2008 2:54 pm Post subject: |
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Sevo wrote:
The hinge and the supports are ok and not bent? And you are positive that you view the image in the right plane and have a infinite target?
Front cell focusing is not mutually exclusive with unit focusing - front cell "focusing" reduces the focal length.
I use a known good camera and lens (Nikon F2 with 55/3.5 and loupe finder) set to infinity as the collimation viewing instrument, and a developed piece of film with test pattern placed in the film plane as the test target. |
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Nesster
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| Posted: Wed Oct 15, 2008 3:06 pm Post subject: |
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Nesster wrote:
| Sevo wrote: |
I use a known good camera and lens (Nikon F2 with 55/3.5 and loupe finder) set to infinity as the collimation viewing instrument, and a developed piece of film with test pattern placed in the film plane as the test target. |
Oh cool, this is the opposite direction from Rick Oleson's http://members.tripod.com/rick_oleson/index-123.html "bringin infinity indoors" article... I like!
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Nesster
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| Posted: Wed Oct 15, 2008 3:17 pm Post subject: |
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Nesster wrote:
In looking at past photos, I'm thinking of the possibility that the film bends enough at 6x9 to mess with the focus... it seems that the photos with the 4.5x6 mask in are sharper.
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Nesster
Joined: 24 Apr 2008
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| Posted: Sat Oct 18, 2008 10:07 pm Post subject: |
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Nesster wrote:
| Sevo wrote: |
I use a known good camera and lens (Nikon F2 with 55/3.5 and loupe finder) set to infinity as the collimation viewing instrument, and a developed piece of film with test pattern placed in the film plane as the test target. |
This was brilliant, as I was all set to do it the other direction 
Worked a treat on three cameras - the Bessa was the best to fix, the other two are of the very cheap lens variety with a red 'flag' infinity stop with the external protrusions. But I got to clean those lenses etc - I was converting my Certo Super Sport Dolly back to a lens from its stint as a pinhole camera.
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Jesito
Joined: 24 Aug 2007
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| Posted: Sun Oct 19, 2008 3:35 am Post subject: |
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Jesito wrote:
There are a few collimator building articles on the net:
http://www.geocities.com/leafshooter/collimator.htm
http://www.kyphoto.com/classics/collimator.html
Jes.
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Xpres
Joined: 11 Dec 2007
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| Posted: Sun Oct 19, 2008 10:22 am Post subject: |
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Xpres wrote:
Good articles Jes - bookmarked, thanks.
For folders I've always used the ground glass and lupe method which I find very easy and effective. I haven't explored the other techniques - perhaps I will. 
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Nesster
Joined: 24 Apr 2008
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| Posted: Mon Oct 27, 2008 10:55 am Post subject: |
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Nesster wrote:
Thank you again - the SLR method works great, it is a great joy to have the Bessa I work the way it was intended to...
large: http://farm4.static.flickr.com/3211/2973403463_d9ee6a6034_o.jpg
large: http://farm4.static.flickr.com/3240/2973403729_b0923fd00b_o.jpg
large: http://farm4.static.flickr.com/3193/2973403985_5da90482dc_o.jpg
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