AFs with Continuous Drive Mode: focus change between shots?

[antialiasing]

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Hi everyone, hope you are all doing well.

With Focus Mode set to AFs and Drive Mode set to "Continuous - Medium Speed", the SL2 (latest firmware) tries to change focus in between the continuous shots from a single shutter button press. I thought AFs means focus does not change in between continuous shots that result from the same shutter button press. Are others observing the same thing? In tricky situations, such as amid heavy fog where only a few branches at the edge of the frame can serve as good focus targets, the camera hunts for focus for subsequent (starting with 2nd) shot and does not shoot continuously. I'm really puzzled & would appreciate any input.

Thanks

Harry

SL2 + 24-280

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[sillbeers15]

For Leica SL series cameras continuous focusing takes place in every shot irregardless of AFS or AFC settings so long as the drive speed selected is 'medium' or lower.

If drive speed 'high' setting is selected, AF is locked on first frame for both AFS & AFC settings (check instruction manual).

The difference in AFS & AFC for Leica (only) differs in priority on either AF or triggering the shot (no successful AF garrenty). However in real life, there is little difference in successful AF even when AFS is selected. For successful AF, it is dependable on the AF type selected (single, zone, tracking, face/body,...), lens selected, lighting/contrast available & size of subject that I've experienced.

[NickT]

The solution to your issue is to use Leica's version of "back button" focusing. That is switch to MF then press the joystick to activate autofocus. They type of autofocus AFs or Af-c can be selected on menu page 4 customise control - joystick. Then press the shutter and the camera will not refocus in the way you have described. 

[sillbeers15]

If non continuous AF is what you're looking for switch to MF and use the back button focus method as NickT has described. On the other hand if continuous focus is what you're looking for select either IAF/AFS/AFC and you can still use the back button focus button. Just do not release the back joystick once you've achieved the focus you are looking for and trigger the shutter release button as and when you wish to take the shot. However it will not solve the problem you've described about hunting for focus due to the inappropriate AF focus area. Chances the focus area you've selected is too large compared to your subject therefore the camera AF lands itself on the background or foreground instead of your subject. Try selecting 'single point' to see if it can resolve your problem.

[antialiasing]

Thank you all. The back button discussion recalls this other thread below. And it's very good to know that high speed makes the camera give up on changing focus between frames.

What appears slight off-topic but was for me key to understanding the control rationale is this: it appears that the back-button-centric strategy in Leica's design is a result of the "culture" that half-pressure of shutter button is AF-L PLUS AE-L, as vs. AF-L-only as is the case of Nikon (by default anyway). So the Leica back button, regardless of whether it is set to AE-L or AF-L, acts first and foremost as an indication that you want AE-L and AF-L to be separated.