Sigma 14-24mm 2.8 art uneven sharpness

Started 7 months ago | Discussions thread
OP blåland Regular Member • Posts: 257
Re: Sigma 14-24mm 2.8 art uneven sharpness

MattiD80 wrote:

I see field curvature in most pictures. Has nothing to do with softness of lens. UWA no matter what has to introduce at at least one focal length heavy field curvature. no way around it. The focus plane is not flat. For that reason, using UWA you should always put 'non important' stuff in at bottom of image. As it's likely out of focus. Then the rest will be fine in focus (F8-F9).

Even the 14-24mm or nikon has it, and similarly the 24-70mm F2.8E VR (wich to my opinion has the least field curvature of any 24-70 on the market). You have to learn it, and calculate it in your shots.

The nikon 20mm F1.8 is a gem in this case. Still very wide, very even (just a hint of sharpness dorp and field curvature at F8). Maybe Sigma 20mm F1.4 art is what you want, though according to anotherMike it has worse corner (but better center) as the nikon.

As a warning to people: UWa photography is complex, with lot of possible things going wrong. Learning them, preparing for them, and choosing the right tool (lens) for job is crucial, way more then 35-600mm focal length). Perspective distortion, normal distortion, field curvature, the general more then other focal length sharpness drop to corners, even though Depht of field per F-stop is deeper at UWA, you gain so much extra info in the image, that usually you still are more 'of a problem' then less of a problem for getting everything in focus, Flare is often a issue, bending of well known ofject in unnatural form (like buildings, human faces, etc). This took me quite some time to learn, and as a result I tempered my expectation of what a 14-24mm lens (my nikon Af-S version) can do. It's still an amazing lens. But you gotta work hard to reduce the downsides of UWA. As a result my respect for the 20mm F1.8 rised up very high after my last travel. Most of the downsides listed are a lot less, it's sharper then zooms, super light, more F-stop, and incredible value if you think about it. It should be no brainer of UWA is your sort of thing, sadly Sony doesn't have it yet. At some point, Sony will make a very nice 20mm prime, there is no doubt about that it's a gap in their portfolio, plus one that shouldnt be hard with short flange distance advantage. My advice, buy it the moment it comes out. For now the 16-35mm GM and 12-24mm Sony lenses seem very nice (but ofc they will have their own character in field curvature).

And expecting this at F2.8? Not realistic. Especially not close to the sensor. Field curvature gets worse at lower F-stop and closer to camera. Two ways to solve it (or combine for stronger fix): Further subject from camera (starting below you usually), and Stopping down. There are no other cures. If it's good at f8, you should be ultra happy, that's already a very capable lens then (trust me for UWA zoom, this is an exception not that rule, that F8 is already good corner.)

Did you see the difference between left and right side?
I'm not new to UWA lenses. Had the Canon 10-22mm for many years and it was my favorite lens until I upgraded to fullframe. The new Sigma is of course a lot better.
The photos are only taken at f/2.8 to test if I got a good copy. I would stop down for actual photography.

At f/8 I'd say the right side is about 90% as good as the left. I only wish they were even.
I prefer zooms when it comes to ultra wides. For 24mm and up it's all legacy primes.

 blåland's gear list:blåland's gear list
Sony a7 Canon EF 100mm f/2.8 Macro USM Canon EF 70-300mm f/4-5.6 IS USM Sigma 14-24mm F2.8 DG HSM Art +1 more
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