Well.. This feels like another jane kok/john kok issue... But genuine this time.. Well ts, if u want f1.8 yet more stuff in focus, try a lens below 20mm. If u can find one
by the way,
i have tested a few.
i found that 50mm f1.8 lens when shooting at f1.8, image quality consistently not good..
even that i am using tripod, i am still able to see a little bit of "blur" on image.
f2.0 or 1 stop ahead will give a lot better image.
but TS, this isn't related to your "shooting wide open why is it blur" question right? your previous question was on DoF. is this a new one? please don't confuse others.
How far is your subject? If it is within 2 meter & shooting at f1.8, the DOF is very thin, probably 10cm or less. You may want to check out it here:
Maybe the user assume that image blur is due to hand shake , hence he/she increase the "shuttle" speed. ( forgetting about DOV)