Digital Contax T and Minox 35
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| These two lenses made the A7 more compact and good for street snap shooting. |
Compact film cameras are so fascinating. Started from Rollei 35 to the latest or the last generation of compact film camera Ricoh GR series, the images that they produced are so amazingly good when comparing to SLR lenses. The size of them is so small and just like a pack of playing cards. Take a look on Minolta TC-1, one motor does all the winding/rewinding/lens extension functions. They are not only the cameras but a master piece like Swiss watches. Nikon 28Ti and 35Ti have the retro watch dial and look really classic. I collected a lot before but they were all sold except few. The only compact cameras that I still have are Contax T and Minox.
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| Taken by Contax T 38mm f/8 on A7 . You can download this image and check the resolution of the centre/corners. |
Contax T is the first compact camera from Contax which was designed by Porsche, having the titanium top case with sapphire shutter release button. The Sonar 38mm f/2.8 lens is so good and it was still used in T2.
Minox 35 is a good performer without RF focusing mechanism. Having a very simple design doesn't mean the images it produced are not good. The basic Minotar's (the original lens used on Minox 35 series) design hasn't been changed for years. (Minoxar is multi-coated and Minotar is single-coated. Minox AF is a different lens ).
On film, Contax T Sonnar 38mm is good even wide opened, soft at corner and here is the MTF of this lens. The MTF graph shows the drop in resolution near to the corner (18mm).
However, it reaches its excellence at f/8. Since it is a Sonnar type lens, the whole lens will be moved in and out when focusing. The lens distance between film plate and the lens is not that critical. But need to readjust the focus after it was implanted onto a camera cap of Sony A7.
On Sony A7, the image corner is not that great. It may be due to the thick filter stack in front of the imager and causing the image smashing. I may try to replace the filter stack one day. But at f/8, the lens is really good.
** Contax T lens on newer Sony A7RII got better corner performance even at f/2.8. (2018_09_10)
** Contax T lens on newer Sony A7RII got better corner performance even at f/2.8. (2018_09_10)
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| Contax T 38mm |
Minotar shows the same corner softness. Implanting Minotar needs more measurements and the distance between the lens and film plane must be accurate due to the fact that it is Tessar-type structure. Any deviation will cause the loss of resolution.
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| Minotar 35mm |
Personally, I love the Contax T 38mm having a rich colour reproduction and a very high centre resolution even at f/2.8. Distortion is low comparing with Minotar.
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| Set the aperture at f/8 and focus at 4m, now you have the free focus camera. Contax T 38mm |
Comments
Yes you can do it but you need to remove the lens from the Minox first. It is not that hard if you decided not going back to use the camera again. You will find there is a set of spring and electromagnet behind the lens. Just remove them and find a way to keep the shutter wide open. Please note that you are not necessary to touch the lens itself and you should keep the focus setting un-touched so you can plant the lens to a plastic camera cap (you can get the cap from ebay)with a correct lens-to-CCD distance at infinity.
Indeed, I refined my conversion by using metal filter cap (also from ebay) and lens reversal adapter for E-mount (I use 52mm filter cap and reversal adapter). Minox Lens is not bad if you are using A7rII.
Leo
Very nice article. Im in the process of trying the same conversion with a contax t lens to leica LTM. Do you, by chance, still have the measurements for the focal plane distance? Or could you tell me how you figured out how far the lens needs to be from the filmplane?