Sigma 8-16mm sharpness tests

Outdoors on my tripod, I thought center sharpness was quite good at all apertures. Corner sharpness was good, and even better at F8 and F11.  Lab tests on various websites indicate that the Sigma 8-16mm lens has excellent sharpness in the center & corners. 

 Center and Corner Tests at 8mm

DSC7909 - At 8mm, F4.5, center, 100% crop

At 8mm, F4.5, center, 100% crop

 

7910 - At 8mm, F5.6, center, 100% crop

At 8mm, F5.6, center, 100% crop

 

DSC7911 - At 8mm, F8, center, 100% crop

At 8mm, F8, center, 100% crop

 

DSC7912 - At 8mm, F11, center, 100% crop

At 8mm, F11, center, 100% crop

 

DSC7917 - At 8mm, F4.5, corner, 100% crop

 At 8mm, F4.5, corner, 100% crop

 

DSC7918 - At 8mm, F5.6 corner, 100% crop

At 8mm, F5.6, corner, 100% crop

 

DSC7919 - At 8mm, F8, corner, 100% crop

At 8mm, F8, corner, 100% crop

 

DSC7920 - At 8mm, F11, corner, 100% crop

At 8mm, F11, corner, 100% crop
 

Center and Corner tests at 16mm

Test photos will be up shortly. The lens was tested at 16mm at F5.6, F8, F11, F16. Center sharpness was good and I could see little difference at different apertures. Corner sharpness was also very good, maybe F8 & F11 were slightly better. Lab tests report very excellent center sharpness, esp. at F5.6, and very good corner sharpness. It's safe to say the lens will not really limit you, only your technique will.

Strange exposure results

In manual mode, at any focal length, shooting the lens wide-open gave the same exact exposure as stopping down 1/3 or 2/3rd's of a stop. Does this mean the lens cheated me out of 2/3rd's of a stop, and was really a F5.6.-F7.1 lens? It would appear so. I replicated this test several times! I'd be curious to see if anyone else saw the same results. It could be I just had a faulty copy.

 Continue to Sigma 8-16mm sample outdoor photos

Comments

I checked out the variation

I checked out the variation of exposure with aperture on mine and did not find the effect you noted. Exposure changed as expected all the way down the aperture range.

I did note however that because it's such a wide lens that I had to be very careful to keep camera position stable, as small movements could cause exposure changes.