I recently acquired both a Sigma 30mm F1.4 and a Pentax A 50mm F1.7. I've been taking test shots to help me understand exposure, and I'm noticing that when in Av mode at a given sensitivity and aperture, my K-x is choosing faster shutter speeds for the 50mm than for the 30mm lens. The light in my house is not at all good today, so everything's underexposed regardless. But I'm wondering if anyone can explain to me why this is happening. Does it have to do with focal length?
Here's some data on what settings the camera used (in Av) for each lens, as well as a couple sample shots.
50mm - F2, ISO200, no flash:
1/400s 0.0ev
1/320x +0.3ev
1/250s +0.7ev
30mm - F2, ISO200, no flash:
1/250s 0.0ev
1/200s +0.3ev
1/200s +0.7ev
Also, PhotoME reports "distant view" for the above 50mm photo and "close view" for the 30mm photo. I sat in the exact same spot for each photo, so what accounts for the difference?
Thanks very much for your help!
Last edited by twokatmew; 02-05-2010 at 12:53 PM.