Originally posted by Blue Even if he meant f1.2 and f1.4, its still a have a stop. There are f1 lenses out there, but Pentax doesn't make them nor can I afford to even mention their name.
I figure he meant 1.7, got the decimal in there and everything.
I also think he's right, it's irrelevant. Instead of an A50/1.4 wide open, you could get away with shooting an A50/1.7 wide open and a half-stop underexposed and bumping exposure up in PP, unless you were at a really high ISO and noise got out of control, or had subject movement. At low ISO, the A50/1.7 might actually take a better image. It's well-known for better sharpness, contrast and flatter field than the f1.4 lenses. The larger DOF covers focus errors too. It's pretty easy to lose that half-stop paper superiority of the A50/1.4 in ordinary shots.