As unbiased as can be please? Help needed.

Started 3 months ago | Discussions thread
XeroJay Senior Member • Posts: 2,123
Re: As unbiased as can be please? Help needed.

Jeff2013 wrote:

Imho, DSLR - even the mighty D850 cannot keep up with mirrorless when it comes to using fast primes wide open. The AF just isn't as consistent or accurate until about f2.8, at which point you're into zoom territory anyway. The Samyang lenses have been discussed as problematic AF many times before though, so I would consider offloading it.

If you're going to be stopping down though, past f4 ish, then DSLR is generally going to perform better than most mirrorless. The A7III is not great with small aperture shooting.

I completely agree with this analysis.

I was first in line when D800E's were introduced and shot these and D810's for about six years. I mostly shoot fast primes, so I think I spent a short lifetime constantly calibrating these lenses to the several bodies that I would shoot. Worse, focus varied between shots at f1.4 (camera on a tripod shooting a LensCal target). I invited other photographers from my camera clubs with D810's to test with this setup and they all had the same problem, to varying degrees. I sent my D810's in to Nikon for repair and they were returned with the comment that they were within factory spec.

To make matters worse, I would need to estimate the distance to subject that I would be shooting at any engagement and calibrate for that distance.... which could change.

Shooting A7RIII's and an A9 completely solved the focus accuracy problem. I think the D850 is an incredible beast of a camera, and I salivate over the specifications, but for the way I shoot, it would likely be far too frustrating and I simply do not want to waste another minute of my life calibrating lenses to camera bodies.

As a note, I realize that the D850 has an internal calibration facility, but I understand that, in practice, it is not as useful as it sounds and it still does not compensate for the shot-to-shot variation, likely caused by the variation in mirror return position.

I think the main problem with DSLRs and fast primes stems from the simple fact that the AF system is actually limited to f2.8 on even the best DSLRs. It's a little known fact, but that AF optical path is simply not taking any phase detect sensitivity beyond 2.8, no matter what lens you have on. It only makes sense that things get further-off the more you open up past 2.8. you can be shooting at f1.4, but your AF system is only at 2.8.

It's one of those things that seems so simple and straightforward that it should be common knowledge in the technical photographic community, but it seems like such an obscured technical tidbit that I don't think most folks are even aware of it.

Mirrorless, on the other hand, is able to use the maximum aperture for AF. This is bound to work better with primes, and it also equals the playing field with low light AF between DSLR and mirrorless. I had heard so many folks claim that the A7III low light AF is poor, only to learn that they're using f4 lenses. I use only fast primes, so I've found the A7III low light AF to be even better than my DSLRs.

 XeroJay's gear list:XeroJay's gear list
Canon EOS M6 Sony a7 III Canon EF 100mm F2.8L Macro IS USM Canon EF-M 22mm f/2 STM Sigma 50mm F1.4 DG HSM | A +4 more
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