Sony A7R IV: Confusing Stop-Down Behavior, Camera Chooses Arbitrary/Unspecified Aperture for Viewing/Focusing
With lenses having manual aperture control such as Zeiss Loxia and the Voigtlander 65mm f/2 Macro APO-Lanthar, everything is straightforward—the manually-set aperture is the aperture in use for viewing and focusing.
Previous Sony mirrorless cameras stopped down the lens to the shooting aperture at all times. While undesirable for many purposes (including creating autofocus errors), this was at least predictable. It’s possible that Sony might change the behavior of previous cameras with a firmware update, so “previous” should be taken as “in previous years”.
In the Sony A7R IV, the aperture behavior for viewing and focusing has changed, whether magnified or not. In my review of the Sony A7R IV:
This new behavior really causes me headaches when doing focus stacking. Nor does Sony document it, leaving open the questions of whether it is relative to lens speed and/or influenced by scene brightness or shooting mode and/or brand of lens and/or firmware of lens and camera.