[Leica] Leica lenses on Sony A7

[roark.paul at gmail.com (Paul Roark)]

>... You are by definition losing quality in those corners ...

The a7r does have inward looking micro lenses.  How they compare to the M9
or M (which use different angles on them) will need tests to answer.  On
the electronic side of the lens mount, however, I do not dismiss Sony.

At this point, I don't see enough information in tests to tell whether the
Sony a7r (different than the plain a7) microlenses are better or worse than
Leica's.  For now, I'd call that an open question.

Assuming there microlenses are competitive, this raises the question for me
of whether in-camera correction profiles are necessarily better than doing
it in the computer in post processing.   The corners are always going to be
darker than the center with any lens; vignetting to some degree is normal.
 However, the corners of wide angle lenses can run into the dynamic range
limits of the sensor.  That is, the corners get so much darker that they
are pushed down into unacceptably noisy values.  Making a noisy image
lighter does not cure the problem.

With a CCD, I don't see any theory that supports in-camera correction being
better than post-processing.  Most of the noise if from the sensor site and
connection between the sensor and the processor.  So for signal to noise
ratio, it's mostly game over by the time the data reaches the in-camera
processor.

With a CMOS, there may be an advantage to in-camera processing.  Where CMOS
gets its lower noise advantages with higher ISOs is by amplifying the
signal at the sensor site to reduce the impact of noise that is acquired in
the transmission of the data to the processor.  However, for a CMOS
in-camera profile to have an advantage over post-processing, it would seem
that the camera would need to accomplish the vignetting correction via
increasing the effective ISO at the pixel site via differential
amplification.  That is, the pixels would need to have increasing
amplifications as the pixels get further away from the center.   I doubt
that the cameras are that sophisticated.  I'm guessing all the corrections
are made in the camera's processor after the data is offloaded from the
sensor.  If that is the case, then I doubt in-camera has any advantage over
post processing aside from convenience.

Time and better testing is all that is going to answer our questions.  The
concept of competition in digital bodies that will take our M glass,
however, is inevitable, and I expect it'll be wonderful news for the high
end, light weight market segment.  Needless to say, the concept of mating
the best German optics to the best Japanese electronics intrigues me.

Paul
www.PaulRoark.com