Quote Originally Posted by vinvin View Post
Hi all,
I'm reusing this thread to ask about testing lens at the shops. I'm planning to get the Sigma 18-50mm F2.8 HSM lens. So to test for sharpness, we can test at f8 to f11(since F16 will be too dark?). At this fstop, there should be uniform sharpness across the image right?

If I put to F2.8, I should check for sharpness at the focusing point as see if I like the bokeh?

I'm not a yim cheem person but just want to eliminate glaring problems when I test.

Quote Originally Posted by vinvin View Post
To add to the above. Should I test with A priority or M? For fast lens, I want to be able to use a reasonable handheld shutter speed(1/60 and above) with F2.8 under low light right to avoid a blurry image as much as possible?
why do people care so much about bokeh, i have no idea, other than the donut bokeh you might get from mirror lenses.. personally i can't see a difference - people only talk about bokeh when they have nothing else to talk about.

i would also test at f/2.8 for focusing problems, but that's jsut me.

do not test the lens handheld. if not test for what? put on the counter, aim it at something with edges (e.g. lens boxes with wordings).. for all you know you are causing shake and therefore sharpness problems.