Performance of a9 focusing stopped down in AF-C in low light?

Started 3 months ago | Discussions thread
XeroJay Senior Member • Posts: 2,339
Re: Performance of a9 focusing stopped down in AF-C in low light?

vett93 wrote:

XeroJay wrote:

Sentenza wrote:

vett93 wrote:

Sentenza wrote:

aSevenArr wrote:

The A9 has excellent low light performance, it’s one of the reasons that I love the camera.

Even when using narrow apertures?

It depends on how low light and how narrow aperture. I have found that I had to widen the aperture at times so that the AF can work reliably in low light.

By any chance, do you remember approx. the light level and the aperture at which it struggled, and then the aperture at which it could focus reliably?

Both A9 and A9II can AF down to -3 EV. Sony may need to up the tech. According to Canon's website, their EOS R can go down to -6 EV.

The EOS R -6EV rating is indeed impressive, albeit that's at F1.2, vs. A9/A9II -3EV at F2.

I wanted to move to Canon RF, because they have great glass, and because the RF bodies always focus wide open (huge selling point IMO compared to Sony E mount), but then I realized that I don't want to carry around an 85mm prime that weighs 2.6 pounds (no matter how optically outstanding it may be). And we probably won't see an RF 85 1.4 before several years (the 85 1.8 will come before the 1.4, and I want faster than 1.8).

The A9 doesn't do this. Sony should implement it as an option. Though I normally shoot wide open with fast primes, so not really an issue for me personally.

AF with aperture wide open and then stopping down to the actual aperture for exposure may create focus shift issues for a lot of lenses. Not a solution in my opinion.

I got rid of my one and only DSLR, a Canon 7Dii, for this reason. I paired it with a Canon 100-400L V2 zoom. I sent the whole thing to Canon for calibration. They did a good job and it was sharp at 400mm F/5.6. But then I stopped down to F/8 and the image was less sharp.

That's why I said "implement is as an option".

 XeroJay's gear list:XeroJay's gear list
Canon EOS M6 Sony a9 Sony a7 III Canon EF 100mm F2.8L Macro IS USM Canon EF-M 22mm f/2 STM +7 more
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