I got my Sigma 85mm a few days ago, and today I took it out a little bit to start to get acquainted with it. I wanted to compare the performance at the various apertures, so I made the following series of shots of the same subject, all shot within a few minutes of each other. The pictures were taken handheld sitting in my vehicle with my elbows braced against the steering wheel and door frame.
I think that all the focus was pretty accurate on all of the shots, except for the one at f/2.8. It should be sharper than it is, so I think that focus was off just a hair for some reason. I went back later in the day and took the shot again at f/2.8, but lighting was different since the sun was near setting at that point. You can see the second f/2.8 shot at the very bottom of this post.
The pictures were all captured in RAW, with very minor adjustments made during developing using Adobe Camera Raw 7.3. A minor Smart Sharpening was also applied in Photoshop CS6. Click on each of the pictures to view the full size image.
I am very pleased with what I am seeing from this lens so far. I'm happy with the sharpness and contrast at f1.4, and it only gets better as you stop down. I think that this subject with bright afternoon sunlight was a little bit of a torture test for a large aperture lens since there were a lot of high-contrast areas with the white paint job and with the tree branches in the background against the sky. Unsurprisingly, there is some CA in high-contrast areas at the largest apertures, but that is not unexpected and is easily dealt with in Adobe Camera Raw with just a few clicks.
Here is the shot at f1.4 again, and then below that the same shot with CA and vignetting corrected in ACR:
And finally, as mentioned above, here is the revised f/2.8 shot since the focus was slightly off on the first one taken during the series. The lighting is different, but you should be able to see that the lens is very sharp at f/2.8. There was a some magenta in the highlights on the headlight, but most of it was easily removed using the purple "Defringe" slider in ACR.
Last edited by Edgar_in_Indy; 04-14-2013 at 11:58 PM.