Only A9, A9m2, and A1 are blackout-free, thanks to his stacked sensor that don't need for mechanical shutter. On all other cameras you need for at least front curtain shutter, ant it introduce a blackout. If you use full electronic shutter on your A7Rv to get out the blackout, you'll meet a lot of issue in most common situation (banding, "jelly" effect, etc)
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