The day before yesterday, Lloyd Chambers published an alert about NEX-7 color shifts that vary with aperture. You can read it here Yesterday, he published an extensive set of photographs showing the effect for many M-mount lenses. To see the report, you’ll have to subscribe to his Digital Advanced Photography report. I recommend that you do that.
I have confirmed the effect. The changes from the baseline, f/8, results take place mostly at wide apertures, and in general show a strengthening of the “purple corner” effect. This is not simply an artifact of his or my test methods, which are different from Chambers’. You can see it in the real world.
Here’s a picture of a frosty meadow made with the NEX-7 and the 35mm f/2 M-mount Zeiss Biogon at f/2:
Here’s the same scene at f/8
Both images are uncorrected.
Next: measurements.
I’m rather alarmed that even a fairly wide lens (35mm f/2 M-mount Zeiss Biogon) displays this effect. All the earlier reports seemed to be with much wider lenses, like the 21mm CV.
Is there an inherent flaw in the design of the NEX7?
I’m guessing that the NEX5n is relatively unaffected by this.
If I’m primarily a JPEG shooter and want to go as wide as, say, 17mm (35mm equivalent), without having to stop down to f8, should I completely rule out the NEX range?
I’ve not seen this sort of thing reported for m43 even on lenses like the 7-14mm Panny. Or do the Lumix’es fix it all in firmware?
A few points:
1) The equivalent lens of a 35mm lens on a full-frame 35mm camera is 23 or 24mm, not 17mm. The multiplier for the NEX-7 is one and a half.
2) I’ve tested the NEX-5, and it’s not nearly as bad for corner color errors. I’ve read that the NEX-5n is more like the NEX-5 than the NEX-7 for corner color flaws.
3) JPEG or RAW, the results look similar for corner color errors.
4) This problem seems to be related to the NEX-7 sensor and its treatment of incident angles greatly different than orthogonal, but both the Leica M8 and M9 have it to some degree.
5) The M9 does some firmware fixes, but they’re not totally successful. Other cameras may do the same. The NEX-7 may tweak things in firmware. See the next comment.
6) If you want a 35mm equivalent and don’t want to mess with correcting corner errors, the Carl Zeiss 24mm f/1.8 is a good bet. Whether because of Sony firmware magic sauce or its inherent design, it has little in the way of corner errors.
Jim