Prime vs zoom sharpness

I just got a Sigma 30mm and was comparing picture sharpness to my Canon 15-85.

MTF tests on review sites say 15-85 should be much sharper:

Sigma 30mm MTF @ f4 = 2117
http://www.photozone.d​e …st-report--review?start=1

Canon 15-85 MTF @ 24mm f4 = 2401
http://www.photozone.d​e …canon_1585_3556​is?start=1


But in my actual picture samples the Sigma is tack sharp in the center starting at f2.8.. By f4 its sharper then any other lens I have.

Have other people had the same finding?
or does my 15-85 have a problem?

The 15-85 test you linked to was done on a Canon 50D. The Sigma 30mm was tested on a 350D. Apples to oranges comparison unfortunately and would have a decent impact on measured outcome.

-Tim

my sigma 30 was slightly less sharp @2.8 than my tamron. In the corners tamron is considerably better. Sold the sigma as its use is too specialized for my taste.

tsdevine wrote in post #15154060
The 15-85 test you linked to was done on a Canon 50D. The Sigma 30mm was tested on a 350D. Apples to oranges comparison unfortunately and would have a decent impact on measured outcome.

^^^
You need to compare test results on the same body (frame size, number of pixels). As soon as you change one parameter, the test results should NOT be directly compared!

Does anyone have real world experience from these 2 lenses?

Is the Sigma 30 sharper then the Canon 15-85?

I've no experience of either but I've seen a friends shots from a 550d and 15-85 and they were impressively sharp. I've read some pretty good things about it too