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Pancolart
Joined: 04 Feb 2008 Posts: 3705 Location: Slovenia, EU
Expire: 2013-11-18
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Posted: Thu Dec 16, 2010 12:18 pm Post subject: Painted point in the middle of enlarger lens |
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Pancolart wrote:
This question might sound stupid but i have few lenses most probably for enlarging and they have painted a point in the middle of one glass element inside. Any idea why? _________________ ---------------------------------
The Peculiar Apparatus Of Victorian Steampunk Photography: 100+ Genuine Steampunk Camera Designs https://www.amazon.com/dp/B0B92829NS |
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Sevo
Joined: 22 Aug 2008 Posts: 1189 Location: Frankfurt, Germany
Expire: 2012-12-03
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Posted: Thu Dec 16, 2010 12:32 pm Post subject: |
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Sevo wrote:
I know blocked lenses from dark field applications in microphotography, where the direct beam from light source to film has to be suppressed. Similar techniques may have been used for the technically related point light sources in enlarging. _________________ Sevo |
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Scheimpflug
Joined: 06 Feb 2010 Posts: 1888 Location: New Zealand / USA
Expire: 2011-11-18
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Posted: Thu Dec 16, 2010 12:59 pm Post subject: |
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Scheimpflug wrote:
I've heard of "center filters" being used to darken the center of wide-angle lenses to compensate for the light falloff at the edges, to balance the exposure across the frame. Perhaps this is an internal version of that? _________________ Sigma DP1, Nikon D40 (hers ), Polaroid x530, Pentax P30t, Pentax P50, (P30t/P50 K-A to Nikon F body mount conversion)
Nikon: 18-55/3.5-5.6 "G ED II DX" (F) Soligor: 28/2.8 (FL->F converted), 135/3.5 (F), 3x TC (F, modified) Kalimar: 28-85/3.5 (F)
Vivitar: 70-210/2.8-4.0 Version 3 (F), Tele 500/6.3 Preset (F), 19/3.8 (F) Minolta: 300/5.6 (SR/MC/MD pending F conversion)
Tamron: 28/2.8 (Adaptall) Panagor: 28/2.5 (FD) Aetna: 300/5.6 (F) Osawa: MC 28/2.8 (F)
Vintage Lenses: Dallmeyer: 1940s A.M. 14in 356mm f4 (ULF->M42) 1930s Adon Telephoto Taylor, Taylor & Hobson: 1880s Rapid Rectilinear 8 1/2 x 6 1/2 11.31in f/8 (LF->?)
Parts Lenses: Nikon 35-135/3.5-4.5 (F), Sigma 70-210/4.5 (F), Nikon 50/1.8 Series E (F) |
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Pancolart
Joined: 04 Feb 2008 Posts: 3705 Location: Slovenia, EU
Expire: 2013-11-18
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Posted: Thu Dec 16, 2010 2:20 pm Post subject: |
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Pancolart wrote:
Thank you both for reply. I only cannot imagine how this center block wouldn't have bad impact on the image produced. I'll make tests. _________________ ---------------------------------
The Peculiar Apparatus Of Victorian Steampunk Photography: 100+ Genuine Steampunk Camera Designs https://www.amazon.com/dp/B0B92829NS |
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Sevo
Joined: 22 Aug 2008 Posts: 1189 Location: Frankfurt, Germany
Expire: 2012-12-03
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Posted: Thu Dec 16, 2010 2:36 pm Post subject: |
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Sevo wrote:
There is no rule that says that apertures must be disc-shaped - donut shape apertures occur in mirror lenses as well. _________________ Sevo |
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visualopsins
Joined: 05 Mar 2009 Posts: 11015 Location: California
Expire: 2025-04-11
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Posted: Thu Dec 16, 2010 2:57 pm Post subject: |
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visualopsins wrote:
Catadioptric (mirror) Lenses have center blocked. (Oh!, now I see Sevo has already said that ).
Another interesting (to me) lens is the Zone plate aperture shape. I plan to experiment with these. _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ like attracts like! ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮
Cameras: Sony ILCE-7RM2, Spotmatics II, F, and ESII, Nikon P4
Lenses:
M42 Asahi Optical Co., Takumar 1:4 f=35mm, 1:2 f=58mm (Sonnar), 1:2.4 f=58mm (Heliar), 1:2.2 f=55mm (Gaussian), 1:2.8 f=105mm (Model I), 1:2.8/105 (Model II), 1:5.6/200, Tele-Takumar 1:5.6/200, 1:6.3/300, Macro-Takumar 1:4/50, Auto-Takumar 1:2.3 f=35, 1:1.8 f=55mm, 1:2.2 f=55mm, Super-TAKUMAR 1:3.5/28 (fat), 1:2/35 (Fat), 1:1.4/50 (8-element), Super-Multi-Coated Fisheye-TAKUMAR 1:4/17, Super-Multi-Coated TAKUMAR 1:4.5/20, 1:3.5/24, 1:3.5/28, 1:2/35, 1:3.5/35, 1:1.8/85, 1:1.9/85 1:2.8/105, 1:3.5/135, 1:2.5/135 (II), 1:4/150, 1:4/200, 1:4/300, 1:4.5/500, Super-Multi-Coated Macro-TAKUMAR 1:4/50, 1:4/100, Super-Multi-Coated Bellows-TAKUMAR 1:4/100, SMC TAKUMAR 1:1.4/50, 1:1.8/55
M42 Carl Zeiss Jena Flektogon 2.4/35
Contax Carl Zeiss Vario-Sonnar T* 28-70mm F3.5-4.5
Pentax K-mount SMC PENTAX-A ZOOM 1:3.5 35~105mm, SMC PENTAX ZOOM 1:4 45~125mm
Nikon Micro-NIKKOR-P-C Auto 1:3.5 f=55mm, NIKKOR-P Auto 105mm f/2.5 Pre-AI (Sonnar), Micro-NIKKOR 105mm 1:4 AI, NIKKOR AI-S 35-135mm f/3,5-4,5
Tamron SP 17mm f/3.5 (51B), Tamron SP 17mm f/3.5 (151B), SP 500mm f/8 (55BB), SP 70-210mm f/3.5 (19AH)
Vivitar 100mm 1:2.8 MC 1:1 Macro Telephoto (Kiron)
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greg
Joined: 21 Mar 2009 Posts: 683
Expire: 2012-12-03
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Posted: Thu Dec 16, 2010 3:45 pm Post subject: Zone Plate Comment |
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greg wrote:
Zone Plate Comment
I do hope you have success with them on a camera. I, unfortunately, listened to my eye doctor/surgeon and had zone plate lens replacements installed during cataract surgery (Restor lens). They claimed I would never need glasses again, etc since the were almost infinitely variable. Well, HALF true, I don't need glasses to function normally, the downside is there is no sharp focus at any distance. They are like a soft focus lens. I have to wear jewelers or reading glasses to actually see a sharp image and the DOF is like an f1.0 lens. |
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Pancolart
Joined: 04 Feb 2008 Posts: 3705 Location: Slovenia, EU
Expire: 2013-11-18
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Posted: Fri Dec 17, 2010 2:21 pm Post subject: |
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Pancolart wrote:
Hey Greg that is too bad to hear. You should have had a Vario-Pancolar installed . _________________ ---------------------------------
The Peculiar Apparatus Of Victorian Steampunk Photography: 100+ Genuine Steampunk Camera Designs https://www.amazon.com/dp/B0B92829NS |
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Pancolart
Joined: 04 Feb 2008 Posts: 3705 Location: Slovenia, EU
Expire: 2013-11-18
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Posted: Wed Dec 22, 2010 10:53 am Post subject: |
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Pancolart wrote:
Vario-Tevidon 18-90mm also has such dot. It has reflective surface towards the front. _________________ ---------------------------------
The Peculiar Apparatus Of Victorian Steampunk Photography: 100+ Genuine Steampunk Camera Designs https://www.amazon.com/dp/B0B92829NS |
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Sevo
Joined: 22 Aug 2008 Posts: 1189 Location: Frankfurt, Germany
Expire: 2012-12-03
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Posted: Fri Dec 24, 2010 11:20 am Post subject: |
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Sevo wrote:
On old TV and cine lenses, in-lens mirrors are not that uncommon as provisions for mirror-out finders - on close inspection you'll see that the dot (indeed the mirror surface) is at 45° angle and semi-transparent, while the lens barrel may have a cover at that side that unscrews to expose a finder socket (but they often did not use a different optical group on budget/CCTV lenses, so the mirror often is there while the finder socket is missing). _________________ Sevo |
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