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ForenSeil
Joined: 15 Apr 2011
Posts: 2726
Location: Kiel, Germany.
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 Posted: Mon Feb 10, 2014 11:57 pm Post subject: Medium Format --> FF/Crop Focal Reducer? |
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ForenSeil wrote:
Hi!
Basically focal reducers are nothing more than loupes.
I've just found an loup from an dirty old slide viewer which magnifies 35mm slide to about 6 cm length.
I tried to use it as an focal reducer (handheld behind a 6x9 lens) - it works but as expected IQ was was not very good, as it was a singlet only which adds a lot abberations.
I wonder if another kind of lens could be used to magnify the sensor / reduce the focal length?
I was thinking about using achromatic doublet from telescopes but cheap ones "only" have 6cm diameter (like http://forum.mflenses.com/meade-astronomical-telescope-291-f900mm-f114-75-on-nex-t54263,highlight,%2Bmeade.html) and I have not idea how to adapt them. Also I guess that they are well corrected for CAs but not perfectly for flatfield, as basic eyepieces generally only have small entrance pupil.
Any more ideas? Do slide viewers exist which have CA+flatflied corrected loupe?
_________________
I'm not a collector, I'm a tester 
My camera: Sony A7+Zeiss Sonnar 55/1.8
Current favourite lenses (I have many more):
A few macro-Tominons, Samyang 12/2.8, Noritsu 50.7/9.5, Rodagon 105/5.6 on bellows, Samyang 135/2, Nikon ED 180/2.8, Leitz Elmar-R 250/4, Celestron C8 2000mm F10
Most wanted: Samyang 24/1.4, Samyang 35/1.4, Nikon 200/2 ED
My Blog: http://picturechemistry.own-blog.com/
(German language)
Last edited by ForenSeil on Tue Feb 18, 2014 12:41 am; edited 1 time in total |
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visualopsins
Joined: 05 Mar 2009
Posts: 11069
Location: California
Expire: 2025-04-11
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| Posted: Wed Feb 12, 2014 1:15 am Post subject: |
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visualopsins wrote:
I have heard of fast f=50mm 35mm camera lens used reversed as a loupe...
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☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ 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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Nordentro
Joined: 24 Jun 2010
Posts: 4713
Location: Lillehammer, Norway
Expire: 2015-01-29
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| Posted: Wed Feb 12, 2014 10:12 am Post subject: |
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Nordentro wrote:
I wish there was a P6 speedbooster/ Lens Turbo 
_________________
Lars | Manuellfokus.no |
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ForenSeil
Joined: 15 Apr 2011
Posts: 2726
Location: Kiel, Germany.
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| Posted: Wed Feb 12, 2014 6:25 pm Post subject: |
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ForenSeil wrote:
| visualopsins wrote: |
| I have heard of fast f=50mm 35mm camera lens used reversed as a loupe... |
Very most of these lenses have small exit pupil so that doesn't make much sense as focal reducer. Even most F1.2 50mm lenses only have a ~40-42mm exit pupil diameter. No not even close to 56x56mm of a P6
Btw. I've tried an 900mm ~F15 (60mm diameter) doublet from an basic cheap telescope. It does work basically but amount of boost is quite small, giving an ~0,9x crop only, as focal length is very long. But most cheap telescopes are 600mm with 60mm diameter and so schould work a little more efficient.
_________________
I'm not a collector, I'm a tester
My camera: Sony A7+Zeiss Sonnar 55/1.8
Current favourite lenses (I have many more):
A few macro-Tominons, Samyang 12/2.8, Noritsu 50.7/9.5, Rodagon 105/5.6 on bellows, Samyang 135/2, Nikon ED 180/2.8, Leitz Elmar-R 250/4, Celestron C8 2000mm F10
Most wanted: Samyang 24/1.4, Samyang 35/1.4, Nikon 200/2 ED
My Blog: http://picturechemistry.own-blog.com/
(German language) |
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CuriousOne
Joined: 31 Dec 2013
Posts: 669
Location: Home
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| Posted: Fri Feb 14, 2014 7:24 am Post subject: |
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CuriousOne wrote:
I also have 150mm/2.8 medium format lens, and getting even 0.5X speed booster would be nice, but have almost no time to take care of that.
Regarding the lens we need, there are several sources, one of them is a projector-like device, but have no idea how this device is called. The device, looks like movie projector, but accepts standard 4x6 photos as input, and projects them onto wall. It has two triplet lens, translucent mirror and other things too. What we need is the bottom triplet lens assembly.
Another source can be an old polaroid instant camera, mounted in reverse, i.e. you project image from your medium format lens to area, where cartridge with film was located, and attach your camera where the lens input is.
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I have nothing to compensate with lens |
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David
Joined: 13 Apr 2011
Posts: 1869
Location: Denver, Colorado
Expire: 2013-01-25
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| Posted: Fri Feb 14, 2014 8:49 am Post subject: |
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David wrote:
Would a reverse-mounted 2X TC work?
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http://www.youtube.com/user/hancockDavidM |
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CuriousOne
Joined: 31 Dec 2013
Posts: 669
Location: Home
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| Posted: Fri Feb 14, 2014 10:23 am Post subject: |
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CuriousOne wrote:
I also had such idea, tried, it does not works but the external (the one that goes in front of the lens) should work.
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I have nothing to compensate with lens |
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ForenSeil
Joined: 15 Apr 2011
Posts: 2726
Location: Kiel, Germany.
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| Posted: Tue Feb 18, 2014 12:46 am Post subject: |
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ForenSeil wrote:
| David wrote: |
| Would a reverse-mounted 2X TC work? |
No, a TC stays a TC when reversed like a loupe stays a loupe when reversed.
The optical block of such a toy might be very good as focal reducer:
Click here to see on Ebay.de
Also maybe some xray or aero surveillance lenses could be used as FR
_________________
I'm not a collector, I'm a tester
My camera: Sony A7+Zeiss Sonnar 55/1.8
Current favourite lenses (I have many more):
A few macro-Tominons, Samyang 12/2.8, Noritsu 50.7/9.5, Rodagon 105/5.6 on bellows, Samyang 135/2, Nikon ED 180/2.8, Leitz Elmar-R 250/4, Celestron C8 2000mm F10
Most wanted: Samyang 24/1.4, Samyang 35/1.4, Nikon 200/2 ED
My Blog: http://picturechemistry.own-blog.com/
(German language) |
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