Inconsistent AF performance with Z6/Z7 - using external flashes

[olyflyer]

Here another example with AF eye detection confirmed and actual focus is somewhere on the ear. The model was static. I am not having any conclusions here. I am just trying to understand what (settings, operator mistakes, anything...) to change or to improve to make it better. I can send the full picture on priv if you want.

Ok. There are several things which can go wrong.

1. You move.

2. Subject moves.

3. You push the release too early.

4. You push the release too late.

5. You twist the focus ring accidentally.

None of that has with flash to do.

Disable the focus ring and enable focus priority. This will not give you 100% hit rate but probably will improve a lot. All of the above except 5 can happen even with focus priority, but will help you out.

... another question is... You did not do any focus tuning, did you? If you did then that might also cause a problem. Regardless what, the very low hit rate you get with TWO cameras indicates user error. I'm 99.99% sure that it's not camera or lens error and has nothing to do with flash.

focus tuning is for DSLR's IMHO. ML has focus detection on the sensor. What is sharp on the sensor is sharp on the picture.

Yes. I know that, but many people believe otherwise, and some don't know better. Focus tuning can however cause a problem.

In DSLR's the focus detection is remote from the sensor, the different route may create focus error. And light metering error using (linear) polarizers.

P.S. looking at the picture, and understanding flash is involved, can the light have been too dim (prior to the flash) to perform AF?

 

[olyflyer]

Ok. There are several things which can go wrong.

1. You move.

2. Subject moves.

Obvious reasons and theoretically can happen, but I am sensitive to be frozen and even holding my breath I believe, so not very probable. Just for testing purposes I'll try how AF-C changes the keepers ratio...

"Holding breath" is in my opinion not a good idea at all. If critical and I expect small movements then I release the shutter just after I out haled while my chest is relaxing just before inhaling. In between I allow the camera to move up and down on the target, and my micro movement is automatically downwards when I shoot. "Stale frozen" doesn't exists, if you try to be rigid then you tremble. Of course, there can be other techniques also, but mine worked fine for me the last 50-ish years.

3. You push the release too early.

4. You push the release too late.

What do you really mean by too early or too late? I believe I push as soon as the focus is confirmed with AF-S, so with a static model it is a right moment. Too early would be corrected by focus priority - right?

Yes, "too early" should be corrected by focus priority, which I don't know if you had it set, but "too late" would not. I mean by "too late" if you wait for the green confirmation and happen to push the button after that then it might lock the focus and the release will be a bit too late, when you or the subject has moved.

5. You twist the focus ring accidentally.

I am convinced I do not even keep my left hand on the lens (usually primes) but on the body.

I learned to keep one hand around the lens. It gives me best stability.

Also I've just checked the ring needs to be turned pretty a lot to initiate manual focus. It is also visualized in the EVF with a focus slider so I would have notice. Nevertheless just in case I turned f2 from M/A to off.

Actually, in my experience, you only need to turn VERY little to throw out the focus, and also the arrows are not that sensitive, and definitely not 100% accurate.

None of that has with flash to do.

I understand there seems to be no correlation. With enough ambient light the AF should work the same way with or without flash. But please notice than in FW 3.40 release notes Nikon claims:

Improved face/eye detection performance and the visibility of subjects in pictures taken using an optional flash unit.

...but that is true. At least true for everyone else except you, but I think your problem is not face or eye detect but focusing in general.

Disable the focus ring and enable focus priority.

It is on focus prio already

OK, good to know, but did you disable the focus ring?

This will not give you 100% hit rate but probably will improve a lot. All of the above except 5 can happen even with focus priority, but will help you out.

... another question is... You did not do any focus tuning, did you?

AF fine tune is OFF.

If you did then that might also cause a problem. Regardless what, the very low hit rate you get with TWO cameras indicates user error.

I cannot figure out what changed my keepers ratio so badly since summer? My first guess was some FW 3.40 bug and that is why I rolled out back to 3.31 and compared results.

I'm 99.99% sure that it's not camera or lens error and has nothing to do with flash.

Lens were changed as well. Will keep trying...

I am out of ideas and you seem to be convinced it is the gear. I think you should send in your cameras to Nikon. That's what I would do if I would be convinced that I do nothing wrong.

Another thing... maybe it would be a good idea to start over and do a rest to factory defaults.

Btw... How did you roll back? AFAIK that's not supported by Nikon.