JVan_02 wrote:
@Juha Kannisto@ I got a question: have you taken the 35mm out in low lighting situations and tried PDAF? Asking for two reasons. The first is that I'm curious how the α7C handles the lens in low lighting. Every -EV AF rating is rated at f2 or brighter, but it seems like Sigma designed this new 35 in the same way they did with their new 85: leaning heavily into the vignette & distortion in an effort to maintain high quality in other parameters while keeping the size down. Wondering if the vignette is heavy enough to affect the -EV AF rating with PDAF.
Secondly, from samples I've been seeing, looks like there's some uncorrected SA in the 35 (slight glow at near MFD). Is there any point in bad lighting where the lens performs notably worse as you get closer?
If these look too involved to test: don't . Just wondering if I went from my 40 to this Sigma if I'd have to deal with lesser versions of the same problems. Thanks in advance if you do!
I have shot with it in some low light situations outdoors with city / shop lights illuminating the scene, and I've not run into any noticeable focusing problems, but I've not especially tested PDAF in those conditions. Usually those scenes have a lot of contrast between the lit and dark areas so it's not really challenging for the focusing system. I'm currently keeping my A7C in AF-A mode so the focusing is a mix of AF-S and AF-C. I've been mostly shooting static scenes and not trying to track any action, so AF-S gets used quite often, but when I prefer to select the focusing area I use touch tracking, which becomes AF-C based real time tracking. Overall I think the focusing speed might be a bit slower compared to best performing Sony lenses but not really noticeably so. I'm largely an MF shooter and before getting these I-series lenses I've been shooting my A7C almost exclusively with MF lenses so can't really compare the focusing speed on A7C to other lenses in detail at the moment. I don't feel like there's any problem though.
About the distortion on the 35/2 DG DN, this Japanese review had some interesting info about it:
According to the review, the distortion changes from slight barrel at infinity to medium pincushion near MFD. Unusual for a prime lens to have such different distortion characteristics depending on focusing distance. This might be a bit tricky to correct manually, and I think with this kind of scenario the lens distortion correction data in EXIF that C1 Pro also utilizes with "Manufacturer Profile" correction setting will be very useful. Vignetting is also covered on the same review page. I've noticed it to be relatively strong wide open but it's not so noticeable when stopped down a bit.
They had very positive findings in most areas, including resolution at infinity, AF and so on, but resolution at near MFD was one area where they had a bit mixed results (e.g. good at center but less good at peripheral areas).
For me the focus acquisition has been fine even in low light and close to MFD but whether the end result comes out perfect (e.g. whether the focused point was in perfect focus in the resulting photos) would require a lot of comparison testing which I haven't done. When using AF at close focus distances and shooting something like small flowers it's often difficult to get the AF focus point right where I want it in those focusing modes that I use (e.g. wide area AF-A first and then touch initiated real time tracking when the camera didn't decide to focus exactly where I wanted). Real time tracking has a rather large focusing box and then it's hard to say where exactly the focus gets placed in a small object like some flower or plant. When I feel like I need more precision in close-up shooting of small objects, I typically switch to MF and use magnification to be able to control the focus very accurately. It could be possible to shoot with different AF modes to make sure to get more AF precision but I prefer to just switch to MF in those situations. That makes it more difficult to evaluate AF performance near MFD though...
Dec 26, 2020 at 08:09 AM
Previous versions of Juha Kannisto's message #15445496 « Pre-order: Sigma 24mm f/3.5, 35mm f/2 and 65mm f/2 DG DN lenses »
. Just wondering if I went from my 40 to this Sigma if I'd have to deal with lesser versions of the same problems. Thanks in advance if you do!