Sharing the video is a better idea anyway…and I can now see what you’re dealing with. I can reproduce the behavior ( 
) on an Intel iMac. Have not tried it on Apple Silicon yet.
I suppose that we see an effect of DPL’s way to handle zoom levels. I consider that way as, er, buggy or not well thought out or not well implemented, short: user unfriendly. Here is what I see in general:
- DPL does not accept all values.
- DPL seems to keep zoom levels “magnetically” until an unspecified threshold is reached, at which the viewer snaps to a new zoom level.
- Adopted zoom levels don’t necessarily correspond to the percentage shown in the box: Manually entering the number shown, e.g. for “fit to viewer” can result in a changed size shown by the viewer.
- Launching a tool that adds a toolbar at the lower edge of the viewer changes the zoom level, if the level that was set before launching the tool is too close to a “magnet” value. When the tool is then closed, the zoom level returns to what was set initially, but not necessarily in all cases.
I see two ways for DxO to fix the issue:
- Get rid of the magnet effect and redraw the image with exactly the zoom level that is set in the box and vice versa. Get rid of the magnet effect and, again, get rid of the magnet effect!
- Replace the zoom level selector by buttons fit, 100%, plus and minus, and make in-between zoom levels unavailable. This could also speed up redrawing, if the levels were set accordingly (e.g. 50% = binning 2x2 source pixels for one screen pixel as well as profiting from Apple’s true vs. shown screen resolution)
Magnetic zoom posts/threads