ScoobaKev said:Hi, your wild guess is quite accurate. The focusing function of most AF lenses is based on colour contrast. With more light entering (f2.8), the colour contrast is more obvious and focusing on the subject is much faster.
However, when the aperture is large (f2.8), the depth of field is very shallow, hence when we shoot macro, we use f22-f40 to increase the depth of field. We make up for the small amt of light through the use of strobes.
I pay a premium for lenses with large apertures when I need to shoot in situations with low light where I do not use any flash.
Going through the Canon's lense list. Most wide angle lense are F2.8 and above. Lenses with very low F value like 1 or 2 normally only present for portraits lenses and zoom, tele lenses for allowing faster shutterspeed.
with my limited knowledge, I believed that
1) there won't be much difference if we are both shooting at F8, using a C-5060 and a C-5050 at the same time.
2) C-5060 have a faster focusing speed than C-5050 after I tested, I remembered photosmart verified that too. So the brighter lense story doesn't really work. The reason I assumed why C-5060 have a higher F value is because it has a build in wide lense, just like C-7070. While C-5050 might have better value available for portraits shots.
3) focus speed depends not only on the lense, it depends on the mechanism that drives the lense and the CMOS that provide the instructions. Which is why USM lenses (in Canon) focus alot faster than non-USM ones, regardless of the F-value.
I believe Olympus is smart enough to use forward technology which they thinks benefit everyone more as a whole.