23rd February 2004, 03:11 PM
i believe it's 72mm.
Originally Posted by sehsuan
23rd February 2004, 03:17 PM
And talking about strange designs: Canon's 24-70/2.8L at the short (24mm) end is about 200mm long - not counting the hood.
23rd February 2004, 03:46 PM
i remember i read somewhere dat focal length divided by the aperture will give u the size.something like 200mm / 2.8 = 71.42mm,i might be wrong
23rd February 2004, 04:29 PM
23rd February 2004, 04:46 PM
F-number is the ratio of diameter to focal length, technically speaking. But the definition only works for a simple convex lens, like the kind you draw in secondary school physics - 1 element only.
The focal length of a real life lens is determined by the angle of view at the sensor/film - ie, despite how it looks or measures, if the angle of view landing at the focus point is a 50mm viewpoint, then that lens is classified as a 50mm lens. (That's why a physical 200mm 24-70 is a '24mm' at the wide end.)
Can read more about it in Canon's Lens Work, at the back of the book. It gives a lot of technical definitions - F-number, focal length, etc.
26th February 2004, 05:24 AM
my old PE teacher who is a photo enthuiast has one.. man.. compared to another fren's F1.8, ythe 50mm one is HUGE . No kidding.
Sighz.. he have all the dream lens too... sighz... good thing is he lets me play with them sometimes.. very nice guy