AFS-S issue - Returning my XT5

Mustafa K wrote:

Erik Baumgartner wrote:

I know it will be in focus with a full-press (at least with all the other Fuji cameras), as the shutter actuation happens at the very moment of focus acquisition precisely where the AF box is positioned - so that's what I usually do. Try it, it's reliable even with moving subjects.

Erik you propose to press shutter button fully (without half pressing the shutter button to wait for the AF green mark) in order to get more precise AF. I assume either lens OIS or IBIS should be active for this.

No, not if your shutter speed is adequate for the situation. IBIS OIS won't hurt, but I only have one lens with OIS (the 50-140) and have not trouble getting properly focused images with all my IBISless and OISless stuff.

Is this decision based only on your experience or do you have any explanation for doing this way?

A full-press will get you an exposure that occurs as close to the moment of focus acquisition as possible and, assuming the AF box was in the right place, perfect focus every time - without the delay and slightly missed focus you will often get with a half-press (often worse with BBF).

Now, if you and your subject remain perfectly still this shouldn't make any difference, but people tend to move, even if they think they aren't. If one person is photographing another person it's twice as bad, especially when working with with a very shallow DOF. AF-S with a half-press and shoot doesn't work with with motion going on, but a full-press does (and usually better than AF-C, in my experience).

When you aren't working with any significant motion and a very shallow DOF a half-press and shoot should work just fine - and it usually does for me and, I think, most people, but there seems to an issue with the locked AF position dropping out (sometimes by a lot) somewhere between the half-press and shutter actuation (or even as the exposure is actually happening - nothing in focus). I don't know why this happens (and it's not OK that it does happen), but it seems to be somewhat lens dependent, and possibly user dependent as well (some of the same people seem to have the same issues with different cameras). Whatever the issue is, AF-S with a full-press is easy and works well consistently, so if anyone is having focusing problems it might be worth a try. it's what I do most of the time.

Using X-S10 and XF 60 mm f/2.4 (macro lens without OIS) out of curiosity I did hand-held several quick tests changing following parameters, while IBIS was active (IS2 mode) and AF-S mode is set:

Mech. shutter (MS), f/2.8, full and half press

Electronic shutter (ES), f/2.8, full and half press

MS, f/8.0, full and half press

ES, f/8.0, full and half press.

Apart from some minor stochastic deviations I could not observe any advantage of full or half pressing for the AF performance.

If what you're doing is working for you then there isn't really a reason to change anything, but if you are, or do in the future, the AF-S and a full-press technique is well worth being familiar with. When all else fails, it tends to get the job done.

This is my aging X-T20 and quirky slowpoke original 56mm f/1.2 wide open near minimum focus distance, with this stupid flower anything but still in the wind. AF-C didn't work consistently (at all, actually), but AF-S and a full-press worked perfectly and repeatedly...

Same goes for speeding Volvos. (60 mph or so)..