Back focus when shooting with pulsed light (R + EF 24-105 via adapter).

[ovdmse]

Hi. The situation of a my friend - Canon R and EF 24-105 via adapter.  When shooting with synchronizers (I tried different models) and pulsed light (shutter speed 1\160), autofocus misses. Focusing on the eyes at the central point. In natural light and with an external flash, there is nothing wrong with focusing.

Which way should we move to fix the problem?

[deebatman316]

We need full names of gear being used. EF 24-105mm is not a complete name. What brand flash are you using. Is it on camera or off camera.

[ovdmse]

Canon EF 24-105mm f/4l is usm
The on-camera flash model doesn't matter, because there's nothing wrong with it. Problems arise precisely when working in a studio with synchronizers and pulsed light.