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DanielT74
Joined: 01 Apr 2011 Posts: 204
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Posted: Wed Jun 20, 2012 3:08 pm Post subject: Vignetting on some C-mounts as you stop down |
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DanielT74 wrote:
Apologies in advance if this is a stupid question, folks.
I have a couple of lovely C-mounts as you probably know which almost cover the APS-sensor wide open with only a touch of vignetting but vignette more as I stop them down.
I have heard people adapting the Schneider 50/0.95 to Leica M8 which is a larger sensor, which got me thinking that perhaps it is the mount opening (which is of course very small in the c-mounts) that gets in the way and whether a change of mount will remove that problem.
I am currently using them on a NEX-5n but if I ever start selling pics I will upgrade to a Leica M14 or whatever it will be in 12 years!
Any insights will be greatly appreciated!!! |
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Nordentro
Joined: 24 Jun 2010 Posts: 4710 Location: Lillehammer, Norway
Expire: 2015-01-29
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Posted: Wed Jun 20, 2012 3:56 pm Post subject: |
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Nordentro wrote:
General rule is that longer c mounts covers a greater area of the sensor A 50mm may cover both ff and aps-c, but a 25mm will have heavy vignetting on ff and less on aps-c... _________________ Lars | Lens collection | Manuellfokus.no |
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danfromm
Joined: 04 Sep 2011 Posts: 576
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Posted: Wed Jun 20, 2012 8:19 pm Post subject: Re: Vignetting on some C-mounts as you stop down |
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danfromm wrote:
DanielT74 wrote: |
I have a couple of lovely C-mounts as you probably know which almost cover the APS-sensor wide open with only a touch of vignetting but vignette more as I stop them down. |
Interesting. Stopping down reduces, doesn't increase, mechanical vignetting. |
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std
Joined: 09 Feb 2010 Posts: 1827 Location: Bulgaria
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Posted: Thu Jun 21, 2012 6:29 am Post subject: Re: Vignetting on some C-mounts as you stop down |
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std wrote:
danfromm wrote: |
Interesting. Stopping down reduces, doesn't increase, mechanical vignetting. |
It depends - it reduces the vignetting till some point ( let say 'f8' ) and after that it starts to increase again. _________________ Stefan
My lens list:
SLR MD: Rokkor 1,7/50 Exakta: Kilfitt-Makro-Kilar E 3.5/4cm; CZJ 2/50 Pancolar;M42: CZJ 2.8/50 Tessar; Mir-1B 2.8/37; Jupiter-9 2/85 T-mount: Tamron 5.9/200; Tamron 6.9/300; Tamron 7.5/400 C-mount: Cosmicar 1.8/50 Y/S: Sun 3.5/38-90, Sun 4/70-210 RF Contax RF: Jupiter-8 2/50; Contax G:CZ 2,8/21 Biogon T; CZ 2,8/28 Biogon T; CZ 2/35 Planar T; CZ 2/45 Planar T; CZ 2,8/90 Sonnar T |
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Orio
Joined: 24 Feb 2007 Posts: 29545 Location: West Emilia
Expire: 2012-12-04
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Posted: Thu Jun 21, 2012 7:56 am Post subject: Re: Vignetting on some C-mounts as you stop down |
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Orio wrote:
DanielT74 wrote: |
I have a couple of lovely C-mounts as you probably know which almost cover the APS-sensor wide open with only a touch of vignetting but vignette more as I stop them down. |
The vignetting is always there
the only difference is that by stopping down it becomes more visible. _________________ Orio, Administrator
T*
NE CEDE MALIS AUDENTIOR ITO
Ferrania film is reborn! http://www.filmferrania.it/
Support the Ornano film chemicals company and help them survive!
http://forum.mflenses.com/ornano-chemical-products-t55525.html |
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DanielT74
Joined: 01 Apr 2011 Posts: 204
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Posted: Thu Jun 21, 2012 10:28 am Post subject: Re: Vignetting on some C-mounts as you stop down |
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DanielT74 wrote:
Orio wrote: |
DanielT74 wrote: |
I have a couple of lovely C-mounts as you probably know which almost cover the APS-sensor wide open with only a touch of vignetting but vignette more as I stop them down. |
The vignetting is always there
the only difference is that by stopping down it becomes more visible. |
This is a very enigmatic statement. I am not familiar with invisible, or less visible vignetting.
The fact with these two lenses is that wide open, vignetting is very slight, on the Schneider just the very extreme bits of the corners are black and a touch of gentle vignetting leading to them. On the Switar gentle vignetting but no black. As you stop down vignetting progressively increases on both lenses. |
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Orio
Joined: 24 Feb 2007 Posts: 29545 Location: West Emilia
Expire: 2012-12-04
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Posted: Thu Jun 21, 2012 2:50 pm Post subject: Re: Vignetting on some C-mounts as you stop down |
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Orio wrote:
DanielT74 wrote: |
This is a very enigmatic statement. I am not familiar with invisible, or less visible vignetting.
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Take a very fast lens, mount it on SLR, set it wide open, and put a finger in front of the lens, almost in contact.
Than look through the veiwfinder: can you see the finger? No. At the most you can see a blurring, and some fall of light.
Now stop the lens down to f/8 or f/11 and look again: now you can see the finger, at least a discernible shadow of it.
There are two origins of vignetting:
1- Optical origin: the glass causes a light fall-off at the edge of the image. This type of vignetting improves stopping down,
because the outer part of glass is progressively excluded from the contribution to the image.
2- Mechanical origin: a mechanical factor, like an object that obstructs the view, or an image circle that is not large enough to cover the frame (your case).
This type of vignetting gets worse stopping down, because the circle of confusion is reduced and the edges of the mechanical problem
(in your case, the edges of the image circle) become more visible (while wide open they are blurred). _________________ Orio, Administrator
T*
NE CEDE MALIS AUDENTIOR ITO
Ferrania film is reborn! http://www.filmferrania.it/
Support the Ornano film chemicals company and help them survive!
http://forum.mflenses.com/ornano-chemical-products-t55525.html |
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IAZA
Joined: 16 Apr 2010 Posts: 2587 Location: Indonesia
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Posted: Thu Jun 21, 2012 11:20 pm Post subject: |
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IAZA wrote:
Wollensak velostigmat 25/1,9 has opposite thing. Vignette reduced if stopped down _________________ nex5, Olympus EPM1, yashica half 14, Canon eos 650 want to see samples of mine? please click My lenses
and My gallery
~Suat~ |
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DanielT74
Joined: 01 Apr 2011 Posts: 204
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Posted: Sat Jun 23, 2012 5:50 am Post subject: Re: Vignetting on some C-mounts as you stop down |
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DanielT74 wrote:
Orio wrote: |
DanielT74 wrote: |
This is a very enigmatic statement. I am not familiar with invisible, or less visible vignetting.
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Take a very fast lens, mount it on SLR, set it wide open, and put a finger in front of the lens, almost in contact.
Than look through the veiwfinder: can you see the finger? No. At the most you can see a blurring, and some fall of light.
Now stop the lens down to f/8 or f/11 and look again: now you can see the finger, at least a discernible shadow of it.
There are two origins of vignetting:
1- Optical origin: the glass causes a light fall-off at the edge of the image. This type of vignetting improves stopping down,
because the outer part of glass is progressively excluded from the contribution to the image.
2- Mechanical origin: a mechanical factor, like an object that obstructs the view, or an image circle that is not large enough to cover the frame (your case).
This type of vignetting gets worse stopping down, because the circle of confusion is reduced and the edges of the mechanical problem
(in your case, the edges of the image circle) become more visible (while wide open they are blurred). |
This makes more sense, Orio, but I tested the Schneider again last night and it is reasonable in the corners wide open and sharp by f1.4, whereas by f8 those corners are black.
So I am still a bit confused... |
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glasslover
Joined: 17 May 2011 Posts: 143 Location: San Francisco Bay Area, CA, USA
Expire: 2013-10-19
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Posted: Sun Sep 02, 2012 10:14 am Post subject: Re: Vignetting on some C-mounts as you stop down |
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glasslover wrote:
Hi!
DanielT74 wrote: |
I have a couple of lovely C-mounts as you probably know which almost cover the APS-sensor wide open with only a touch of vignetting but vignette more as I stop them down.
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Unlike others, I don't have an explanation for the phenomenon, but I see it the same as you in some of my C-mount lenses. In fact, I just uploaded a series of photos to this website that show it quite clearly. See below for more information:
http://forum.mflenses.com/viewtopic.php?t=52439&sid=d2adbf8839d346d11bc6cb53e78cacc1
Is this similar to what you see?
Cheers! _________________ --Glasslover
I have a panasonic gh2 and olympus om-d e-m5 (both m43) and use mf lenses of many types |
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