Studio Tests (APS-C)
The Sigma 35mm F1.4 DG HSM performs extremely well on APS-C in the studio, matching or surpassing any other lens in its class (although the differences aren't necessarily huge). Sharpness is impressive even at maximum aperture, and just gets better on stopping down. Distortion, CA and vignetting are all very low too.
|Sharpness||Central sharpness is impressively high even at F1.4, and there's relatively little drop-off towards the corners too. Things only improve on stopping down, with truly excellent cross-frame sharpness from F2.8 to F8. Diffraction starts to degrade the image at smaller apertures, but F16 is still eminently usable if you need the extra depth of field.|
|Chromatic Aberration||Lateral chromatic aberration is exceptionally low. There's a tiny amount of red/cyan fringing towards the edge of the frame, but you'll have to look very closely to see it.|
|Vignetting||Vignetting is negligible, as usual for a full frame lens used on APS-C.|
|Distortion||Distortion is extremely low, with just a little barrel-type visible if you look closely.|
We'd never really consider a 35mm F1.4 to be the ideal candidate for close-up work, and the Sigma is no different to any other. Its measured maximum magnification using manual focus is 0.21x, fractionally higher than specified but still pretty typical for its class. Note though that SLRs won't generally autofocus quite this closely.
Image quality is rather impressive. At F1.4 central sharpness is very decent, but a little longitudinal chromatic aberration is visible and the corners are slightly soft. But this all cleans up quickly on stopping down, with the centre of the frame becoming extremely sharp at F2.8. By F5.6 our flat test chart is critically sharp right across the frame, with practically no chromatic aberration and just a little barrel distortion.
Specific image quality issues
As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests. Here we're looking at issues specific to APS-C users; for a fuller picture, be sure to read the next page too.
Lateral Chromatic Aberration
The 35mm F1.4's CA profile means that colour fringing towards the corners of the frame is slightly more visible on APS-C cameras, compared to full frame. But even so, it's far from problematic, and can be corrected in post-processing where necessary. Nikon SLRs will also compensate for this in their JPEG processing, but other brands won't. The example below shows what to expect - there's a little red/cyan fringing along high contrast edges, but it's not really objectionable even in the extreme corners.
|Canon EOS 650D, F8||100% crop, bottom left corner|