Originally Posted by peachpuff
My s8 and s9 did it, so it seems like its normal.
Just received my S10+ today, so I have the same confusion as OP since it's my first Samsung phone. Does the diaphragm change even for switching from photo to video? This seems quite unnecessary given no change in light condition and can eventually cause wear and tear.
The only time it didn't change was when I switched from Slow Motion to Super Slow-Mo.