Sony A7 Thin Filter Legacy Lens Upgrade by Kolari Vision
FROM KOLARI VISION WEBSITE about their Conversion for better performance with Leica M mount glass..
INTRODUCING OUR NEW THIN-FILTER CONVERSION
As one of first full frame mirrorless camera, the Sony A7-series (A7, A7r, A7s, A7II, A7RII) holds a lot of promise for users of legacy 35mm lens, thanks to it’s short flange distance and wide range of adapters available. Unfortunately, these cameras have less than optimal performance on many classic lenses owing to the extra glass of the lowpass/IR filter that is attached directly to front of the sensor. When these lenses were originally designed for film cameras, there was nothing between the lens and the film, so adding an element to the optical path causes degradation of the image, particularly toward the edges/corners. Our friend Roger at LensRentals wrote some excellent articles explaining the science behind this that you can find here. The Sony A7 series is particularly problematic since it uses a very thick sensor filter which makes many otherwise excellent lenses unusable at the corners by ‘smearing’ the image – something (unlike vignetting or color shift) that cannot be corrected later.
Michael Demeyer, a photographer in San Francisco, approached us and suggested using our experience in IR modifications, where we replace these sensor filters, to improve the A7-series performance on Leica and other rangefinder lenses by replacing the filter in these cameras with a thinner version. He loaned us a Leica M-mount Voigtlander 21mm Color-Skopar F4.0 lens, widely known as problem because of it’s very short exit pupil distance, to use for development.
We are pleased to announce that, after 4 months of development work, we are able to offer this service – a thin filter replacement for the Sony A7-series that significantly improves corner sharpness of legacy lenses (especially wide-angle rangefinder lenses) compared to the stock cameras. Using the same techniques proven in our successful IR modifications, we install a much thinner filter (of Schott optical glass) and then recalibrate the focus on the camera to compensate for the thinner glass. With continuing developments, we are now installing an even thinner corrosion resistant version of this filter that is durable even in humid regions.
We are also now finally able to support the A7II and A7R II for conversion. We wanted to be sure that our conversion was able to maintain proper IBIS stabilization features and wanted to have it tested independently to eliminate any bias. Jim Kasson has done some extensive quantification on the level of shake reduction the A7II can reach, and he agreed to test our A7 II mod. He went above and beyond and developed a system to accurately shake the camera, and his conclusion was “It’s clear that, in this case, the IBIS operation is in no way impaired by the Kolari modification.”