Focal length does not determine how sharp your picture will be. Rather, focal length determines the field of view. With a wide lens (say 24mm), you can see a wide field; with a tele lens (say 200mm) you see a narrower field. See how focal length affects composition here: http://en.wikipedia.org/wiki/Angle_of_viewcyberkid said:Hi buddies, thanks for ur reply..
I still hv some physics questions on camera need to be solved.. Hope u can help me...
For prime lens such as Canon 90 mm which has 1 fixed focal length(for example only), does this mean tht only things which are 90 mm from us will be clearly focused? Other wise, it will be blurred?
If this is true, how r we going to know whether the subject to be capture is 90 mm from the lens? Does this gotto do with the Auto Focus? Wah, how intelligent is the camera!!!
What if the subject is not at 90 mm ? Say >90mm or <90mm?
Prime lens are for quite specific applications (usually macro, super tele, etc) and they aren't usually required (of course depending on what you shoot). Zoom technology has vastly improved from the past and generally pose no problems even with comparatively slower apertures.
