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alex ph
Joined: 16 Mar 2013 Posts: 1674
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Posted: Sun Jan 28, 2018 3:41 pm Post subject: Quite an unusual Minolta lens |
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alex ph wrote:
Out of curiosity I've got a couple of Minolta lenses which were part of a microfilm printer.
From outside they look almost like any projection lens, but with a dented ring around.
And when you look inside... there is a prism which is put over the front lens.
The lenses are x29 and x33. They only focus very close macro mode and have a very short distance to sensor. I could make "freelens" shots fitting the lens directly to the mount ring of my Nex-5N.
The bokeh is smooth but it seems to me I never arrive to get the appropriate pin sharpnes which any reproduction lens should have.
And as you see, the lens gives a mirror inverted Alice in Wonderland image thanks to the prism.
Maybe you have an experience with such lenses nad got better results than I could have? I presume, the alignment of the lens to the sensor should be much stricter, and the quick result I've got is compromised with quite an approximate orientation to the sensor.
As for the lens itself, I tried to count bulb reflexions. As seen, all elements are coated. But I am confused, is it 3 or 5 reflexions? I mean those two fader ones are just ghosts, the ones from cemented elements or "normal" ones from another two elements?
I ask myself what if I unscrew the prism, aside the mirror effect disappear, could I have a better distance to focus and easier way to get the sharpness?
Overall, a cute item, isn't it? |
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visualopsins
Joined: 05 Mar 2009 Posts: 10983 Location: California
Expire: 2025-04-11
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Posted: Sun Jan 28, 2018 8:56 pm Post subject: |
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visualopsins wrote:
I think unless somebody else knows you will try removing it and show us! _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ 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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alex ph
Joined: 16 Mar 2013 Posts: 1674
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Posted: Mon Jan 29, 2018 3:00 am Post subject: |
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alex ph wrote:
You are right! I will wait some time if the expert knowledge comes from the forum members. If not, will set myself to disassemblying.
Meanwhile I thought over the mode the lens was used initially and figured out that I might wrongly oriented it for the first test shots. I put it with the "mount" side to the camera mount and stretched the prism towards the object. But then I said: maybe in printing microfilms that should be the contrary, the prism side towards the film, and the lens side is projecting the image. Maybe?
So I turned the lens bottom up and here are results, mostly from the 33x which seems to be sensibly brigther, by the way, than the 29x. Like one or two stops.
#1
So, the image comes much closer now, like in real macro. These are not crops but full images resized. And I have no way to get a wider angle. That makes me ask how the heck they were used in microfilm printig, with such close focusing distance from the both sides.
#2
The images also become better focused (if I may say it like that), at least in a very tiny zone. But the issue remains the same, I don't arrive to have a shot which seems a "normal" one, with a selected sharpness point. All the shots give an impression of my hands shaking hard or, at best, of a special OOF effect.
#3
So, I take another attempt and shift from keyboard buttons to a more conventional object which is a piece of coin. This one is with 33x and the next is with 29x.
#4
Is not that strange? Well, the keyboard button #2 even pleases me quite a bit (its top left corner), as it has an aspect being made of moving sunlight spots. But there must be another way to use this lenses to print A4 paper sheets from microfilms, right?
The next shot is just to give you a proof of normality. I took a normal Hexanon, put a 100mm projector lens on its front lens and that gives a kind of macro. As you see, even handheld it is finely handled.
#5
Hmm... |
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kds315*
Joined: 12 Mar 2008 Posts: 16641 Location: Weinheim, Germany
Expire: 2021-03-09
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Posted: Mon Jan 29, 2018 6:54 am Post subject: |
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kds315* wrote:
These are lenses from a microfiche reader with x29 and x33 being the magnification factors
(29x, 33x). The built in prisim is to erect the image. Not really that useful those lenses these
days. _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
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alex ph
Joined: 16 Mar 2013 Posts: 1674
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Posted: Tue Jan 30, 2018 3:09 am Post subject: |
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alex ph wrote:
I easily unscrewed the lens "hood".
Just to discover that the screws fixing the prism plate to the barrel are glued.
So I have to find a solvent and a stronger (longer) screwdriver than my tiny watch ones. The further disassembly is delayed.
What is interesting, the prism is tall. It seems to arrive up to the front lens.
Looking from outside I had an idea that the prism was short, with a large air space between it and the lens. |
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alex ph
Joined: 16 Mar 2013 Posts: 1674
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Posted: Thu Feb 15, 2018 3:39 am Post subject: |
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alex ph wrote:
I dismantled the prism. Finally, that was not difficult at all, the screws only seemed to be glued. Here is the lens:
#1
And here is the prism pulled out.
#2
What result that gives? A nice macro-lens. Without the prism the lens is in focus at several centimetres, with quite a pleasant OOF rendering.
#3
The colours are natural (no post-processing).
#4
And shots are sharp (a 100%-crop, unprocessed).
#5
Here is a demonstration of the sharpness it gives.
#6
A 100%-crop of the previous, unprecessed. Please note the paper texture in focus.
#7
The same subject, with the lens reversed.
#8
Another type of surface, straight view, unprocessed.
#9
The same, with the reversed lens, unprocessed.
#10
Not bad at all. What would you say about it, if taken as a dedicated macro-lens? |
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Lightshow
Joined: 04 Nov 2011 Posts: 3666 Location: Calgary
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Posted: Thu Feb 15, 2018 5:01 am Post subject: |
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Lightshow wrote:
The results look much more usable. _________________ A Manual Focus Junky...
One photographers junk lens is an artists favorite tool.
My lens list
http://www.flickr.com/photos/lightshow-photography/ |
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