12 mm f/2 tested at photozone (distortion = so-so borders?)

Started Aug 25, 2011 | Discussions thread
sacundim
Senior MemberPosts: 1,111
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Re: Wide open ..
In reply to zxaar, Aug 26, 2011

zxaar wrote:

sacundim wrote:

"The EF 24mm f/1.4 USM L II produced a roller-coaster ride regarding its resolution characteristic across the tested aperture range. The center performance is perfectly fine but the critical borders/corners aren't overly impressive at f/1.4 - the borders are acceptable whereas the extreme corners are downright soft here. The situation improves slightly at f/2 but you really need to stop down to f/2.8 to get a decent resolution across the image frame. The good news is that the global quality is great between f/4 and f/8 - the center is especially outstanding at f/4."

Wide open for F1.4 lens is at f=1.4 and not F2. You can not compare F1.4 lens's f1.4 performance to F2 lens' f=2 performance.

I've highlighted the part of the quote that answers your concern. Though I will say: I know it's not an exact comparison, but still, it's one of the closest comparisons.

Zeiss ZA Distagon 24mm f/2 SSM (for Sony Alpha full frame):

http://www.photozone.de/sonyalphaff/568-zeiss24f2ff?start=1

"The center resolution is very high straight from f/2 and the border performance is more than acceptable as well. However, the extreme corners are relatively soft at this setting. The image quality is generally very good at f/2.8 with an exceedingly sharp center. The global peak performance is reached around f/5.6 with an exceptionally high quality across the whole image field."

Keyword here is relatively , it does not tell whether it is worse than the 12/2 you are comparing it with. The relative part here is comparison with center. This may still be better than 12/2.

There's an inevitable comparison issue that comes down to sensor size, since the measurements we're looking at are line widths per picture height at MTF-50, and a full frame sensor is 24mm tall while a 4/3" sensor is only 13mm tall. Ignoring sensor issues like pixel density and antialiasing filters, this means that right off the bat you expect full-frame to have like an 85% advantage over 4/3", for lenses with equal optical resolution in line widths per millimeter.

Still, the MTF-50 corner resolution for the 12/2 is about 76% of the center resolution at the same aperture. In the Sony lens, it's about 65%. The Nikon f/1.4's corner are about 61% of the center stopped down to f/2.0, 80% stopped down to f/2.8.

And if we normalize the resolution numbers by sensor height, the 12/2 wins. Granted, this is a bit of an inconsequential comparison, because (a) clearly the FF systems produce higher output resolution than the m4/3 system, (b) we're not normalizing for factors that would affect sensor resolution per mm (pixel density, antialias filter differences). What this suggests, however, is that the 12/2 has better optics than either of these two other lenses—but not better enough to make up for full frame's extra 11mm in frame height.

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