[Brightcolours]

Hello,
 
I just picked up a used Nikkor 28mm 2.8 AI-s. A very nice lens, especially the close focussing distance of 20cm is amazing. 
 
It's commonly described as top-notch and very sharp, according to reviews it should be better than the Sigma 30mm 1.4 EX DC HSM and of course the 18-55mm Canon kit lens.

Which reviews actually test the lens for real? Usually, the 28mm f2.8 Ai-S is just tried on FF and just a subjective opinion is given. It is still a nice lens, but contrast wise it can't keep up. The Sigma usually is downgraded for contrast, but that is when shot wide open. At f5.6 it is performing well, contrast and sharpness wise.
The 28mm f2.8 usually is used on FF, stopped down for landscape stuff. 

I did quick comparisons and was surprised though.
 
https://www.dropbox.com/s/zcqk113jhbhzoq...center.jpg
https://www.dropbox.com/s/ru6b2z7zz81te9...ter-02.png
https://www.dropbox.com/s/14ypgy78prp0vh...corner.jpg
(Canon 600D, f/5.6, 1/96s, ISO400, Adobe Camera Raw 6.3, manually focussed via liveview, 5x magnification and a screen loupe)
 
To my eye the Sigma appears sharper and more contrasty.
Why is that? Possible answers I could think of:
 
A.  It's about good/bad copies
B.  Reviews may be biased in favour of "underdogs", older manual lenses
C.  MTF50 comparisons are not necessarily meaningful
 
 
I bought the lens at a camera shop, rated 'Good', clearly used but only little marks. The focus ring has a tiny bit of play, the glass is all clean.

Try the lens in normal photography situations. It still performs pretty ok. It is not strange that a much newer design like the Sigma, when stopped down to f5.6, shows less field curvature and a bit more contrast. You still can enjoy each lens.

 
 
Best regards,
 
Dan