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M42 Infinite Focus Failure in Full Spectrum

Started Mar 23, 2018 | Discussions thread
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xpatUSA
xpatUSA Forum Pro • Posts: 23,016
M42 Infinite Focus Failure in Full Spectrum
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I bought a M42 lens for full spectrum/IR work, mainly because of the IR mark at the focusing ring. Here is my first effort with that lens:

SD14 with dust protector removed

The lens was set to infinite focus. Previously, I had focus-bracketed from the hard stop down to the IR mark but focused at the stop was the sharpest.

Lots of RT work in the above, including wavelet processing and deconvolution sharpening. Hard to tell because of the heavy processing, but nevertheless the appearance is one of failure to achieve infinite focus.

According to Wiki, M42 registration distance is 45.46mm, Sigma SA is 44mm, leaving an adapter flange of 1.46mm, theoretically and My Kipon adapter flange measures at 1.38mm.

I'll try the same shot tomorrow with the SD15. Meanwhile, any thoughts from those with more M42 experience than I ... ?

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Ted

 xpatUSA's gear list:xpatUSA's gear list
Panasonic Lumix DMC-LX1 Sigma SD9 Panasonic Lumix DC-G9 Panasonic Leica DG Macro-Elmarit 45mm F2.8 ASPH OIS Sigma 17-50mm F2.8 EX DC OS HSM +11 more
Sigma SD14 Sigma SD15
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