Responding to a person on DPR who accused the X of having a soft lens, I did some resolution testing.
Setup:
- Camera set up at 6' distance from my usual target, a very busy bookcase.
- Image processing settings: Standard, Super Fine JPEG, 16M, + DNG set.
- ISO locked to 200.
- Shutter set to A mode.
- Focus mode set to Spot.
- Camera on sturdy tripod. Each frame exposed with 2 second delay.
- Series 1: Each frame is allowed to AF on the same target.
- Series 2: Manual focus on target point, focus setting not touched throughout test afterwards.
- Each frame stepped the lens aperture, first from f/1.7 to f/2, then in whole stops to f/16.
Results:
- Examining the JPEGs at center, right edge, and top left corner, ALL frames are acceptably sharp and crisp. The right edge and top left corner improve slightly from f/1.7 to f/4, center is virtually unchanged. A small degraded (presumably diffraction) sets in at f/11.
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- Examining the DNG files, processed at the LR 5.6 defaults (sharpening = 25 on LR's), all frames show distinct need for input sharpening with slightly soft rendering through all apertures. Moving the sharpening to 40 nets nets sharpness equal to the JPEGs at all aperture settings. Moving the sharpening to 50 nets increased sharpness with minimal halo'ing, again all frames.(For example, even at f/1.7, 5 point type locate in the corner of the frame at 6' distance is clearly readable with 2:1 magnification). This implies that the Leica X sensor has a medium strength AA filter, since the same correction produces the same improvement across all apertures. It also demonstrates that focus shift is extremely minimal (via the manual focus tests).
The same test of the X2 in 2012 showed significantly more variation in corner and edge quality from f/2.8 to f/5.6, and also needed additional sharpening of the DNG files, of a similar nature, determining again that the X2 has similar strength AA filter.
When next I have time to do so, I will repeat the same test with the Leica M9 and the Color Skopar 35mm f/2.5 and the Sony A7 fitted with Leica Summicron-R 35mm f/2. (I don't have a Summicron or Summilux 35mm in M mount at my disposal at present.) It will be interesting to see how those two compare.
But be that as it may, I cannot see any evidence to support the statement that
"the lens is soft and only starts to deliver the 'Leica-magic' from f/5.6." As far as my test shows, the Summilux 23mm f/1.7 on the Leica X is a very high quality performer across all f/stops. It's sweet spot is broad, best performance ranging from f/2.8 to f/11 when diffraction starts to intrude on ultimate resolving power.
Beyond the evidence of this resolution test, I was at the annual All Italian Day car and motorcycle show with the Leica X today. I made about 80 exposures at all apertures, using primarily autofocus on "Face Detect/11 frame pattern" mode. Every frame is crisply, clearly focused, and all frames show beautiful sharpness. At the wide open end of the spectrum, defocus bokeh is beautifully progressive and lacks any jangly feeling even wide open.
IMO, this is a stunner of a lens, fully deserving of the name Summilux.
(Unfortunately, pictures will have to wait. I have other commitments this evening and best get to them now. Maybe later if I get done early. )
G