I am a long-time orig A7R user, shooting with a few GM lenses (24/1.4, 35/1.4, 50/1.4, and 135/1.8). I recently picked up the A7RIII mainly for the IBIS and improved AF, but honestly, the experience so far has been a bit underwhelming — especially considering the added weight. It has the latest firmware 3.10
IBIS: With the original A7R, my usual practice is to shoot around 1/(2×FL) shutter speed and getting pretty consistent results in decent light. With the A7RIII and its claimed 5 stops of IBIS, I expected to comfortably shoot around 2/FL or even 3/FL. But in real-world use (with both the 50 and 135mm), anything slower than 1/FL is unusable. That’s about one stop of improvement at best, or may be 2 stop if error on my part but nowhere close to the advertised 5 stops. Maybe I’m doing something wrong, but the difference feels marginal.
I have been shooting for years without IBIS and have a pretty steady hand, so I don’t think this is a technique issue.
Have you tried to shoot your A7RIII in EFSC or even full electronic shutter mode to see if there is a difference in handheld shooting with critically long exposure times, compared to shooting with full mechanical shutter?
If not, I would recommend to try that. Why that?
I developped a preference for EFSC for handheld shots based on the shooting experience with my A7IV, which in full mech shutter mode has a shutter shock impulse I consider rather noticable. That impulse may have an impact on handheld shots, so unless I shoot something that would benefit from full mech shutter like a fast lens wide open, I shoot it in EFSC as default shutter mode.
Besides, my A7C2 only has EFSC anyway and its shutter sound and impulse I consider significantly softer.
Cheers,
Ralf