My Experience with SL/SL2 Autofocus

[Luke_Miller]

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Here some things I learned after taking about 5K images with my SL and SL2.

1. Leica SL/SL2 autofocus is different from that of my Nikons. Not talking just about Nikon being PDAF and the SL/SL2 CDAF, but other basic differences.  Most of my early difficulties arose from me not realizing this.

2. I use the back button autofocus technique.  My normal setup is the camera is in AF-C.  For a static subject I focus using the back button, release the back button, recompose and take the shot.  Works great with Nikon, but not with my SL bodies.  The Nikon locks focus when I release the back button in AF-C while the Leica does not. So about two or three out of ten SL/SL2 shots will be slightly out of focus. Presumably because when I released the back button the AF system was in one of its focus hunting cycles and the camera stopped focusing while still slightly out of focus.

3.  However, if I don't release the back button and let the SL/SL2 continue to autofocus while I take the shot all the images are in focus.  

4.  CDAF seems to always find focus. I rarely have an image where nothing is in focus, but, early on, the in-focus region was not always where I wanted it.  This is another difference between the SL/SL2 and my Nikons.  PDAF will almost always achieve focus where the focus point is located, while CDAF is more easily drawn off by something with high contrast adjacent to the focus point.

5.  Putting the SL/SL2 autofocus system into Dynamic (Tracking) mode allows me to see what the camera has elected to focus on.  If it is not on my subject I will refocus and find something on the subject with which AF is happy. I rarely miss focus this way.

6.  To summarize, with the SL and SL2 I am always in AF-C and Dynamic (Tracking) using the joystick to activate autofocus.  I keep autofocus active until the shutter is released with both static and moving subjects.  Since I still shoot with my Nikons, I set them up this way also to maintain commonality.  Works fine with them as well.

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[Virob]

Thank you very much for that. I stick with AFs almost exclusively not having had much luck with AFc, but will give it another try keeping your comments in mind.

[Sandokan]

Speaking about the SL, I also use backfocus with AF-s. The AF square goes green when focus is achieved so I have not seen your issue. I also move the focus point to my subject; not having it in centre then recomposing where with geometry, the point of interest may no longer be inn the focal plane. 

[Luke_Miller]

7 hours ago, Sandokan said:

Speaking about the SL, I also use backfocus with AF-s. The AF square goes green when focus is achieved so I have not seen your issue. I also move the focus point to my subject; not having it in centre then recomposing where with geometry, the point of interest may no longer be inn the focal plane. 

Yes, focus and recompose in AF-S can be a bit risky unless stopped down.  Now that I use AF-C and Dynamic (Tracking) I can gain focus on the subject and compose without worry.  The focus box will automatically remain on the subject while I compose the shot showing me that the focus point is still where I want it.  I can now use wider apertures to separate the subject from the background.

[algrove]

Never an issue by using back button AF while in MF mode which then separates the AF from the exposure.  In this way I control all aspects of my capture while being able to move my composition and recompose which in this case does not change the focus point. Functions just like an M as far as focus and recompose goes.

[Stuart Richardson]

I have used AF-S only for nearly the entire time, including back button focus and cannot recall a single instance where the focus was not correct. I don’t have fast moving subjects, but if your subjects are not moving around rapidly, I would recommend avoiding AFc entirely. It has never been good on any AF Leica I have ever owned (mostly the S and T bodies).