Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: chrismuc on January 30, 2019, 05:11:08 am
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The shortest focal length for the Contax 645 system is the 35f3.5 lens which roughly equals the FOV of a 21 mm lens in 135 format.
In order to achieve a wider FOV with this 645 mirror refelx camera, one can consider to adapt 135 PC lenses of shorter focal length with an image circle of at least 67 mm. Unfortunately, the back lens of most 24 or 28 mm PC lenses will intrude too far into the camera body (especially when focussing towards infinity) and therefore interfere with the mirror movement. I examined this issue many years ago when converting a Schneider 28f2.8 PC lens to Contax 645 mount. The excellent and popular Canon EF 24f3.5 TSE II is also not suitable for such a conversion. One reason is the back lens interferes, the other is that the aperture cannot be closed manually.
Recently at Ebay the offer of a Samyang 24f3.5 PC lens, converted to Contax 645 mount popped up. I was not aware that the position of the back lens of the Samyang 24 allowed free movement of the mirror Contax 645, that was positive news. One might expect an image quality of the Canon 24 TSE on a 54x40mm sensor, but the uniqueness of that lens - camera combination seemed worth the investment.
The lens is pretty small on the camera, compared to normal 645 format lenses.
It focusses well to infinity, and the corner sharpness is pretty even at all four corners.
To achieve a good corner sharpness one has to use the lens at f9.5-11, I set it to f11. I hardly ever use lifeview on my IQ180, using the tripod, I simply make a few shots varying a bit the focus, all the time zoomed in to 100% at the IQ. So one can find the best focus quite easily.
The lens shows some light fall off and a bit of color cast. These two effects I compensate by creating and using a CornerFix profile. CA and the rather strong linear distortion are reduced in AdobeCameraRaw.
I had only a few opportunities to test the lens, the quality looks quite usable.
Enclosed a few sample pictures.
Btw., the newly released NSW 23f4 Apo lens also looks very suitable (and the optical quality exceptional) to be used on 645 format mirror reflex cameras with digital backs like Contax 645, Hasselblad H, Pentax 645, Mamiya 645 / PhaseOne XF via Hasselblad V mechanical adapters ... if the back lens has some clearance to the mirror of the camera. I already asked NSW if they tested such applications which would extend their business options beyond the usage as a shift lens on 135 size mirrorless cameras or the GFX.
Enclosed two pics. Sorry, one has a bit heavily HDR look ;-)
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Very cool ...