tscales@xxxxxxxxxxxxx writes:
<< The f/4 and f/3.6 are great, but bigger, heavier and usually more
expensive. >>
I dislike zooms in general but I recently bought the ("360 ball bearing")
f/3.6 and would point out an interesting characteristic. As the zoom focal
length increases the zoom gets substantially shorter. Without thinking about
it too deeply one might guess that the lens would get longer as the focal
length increases. I checked a Vivitar series 1, 28-90mm f2.8 varifocal zoom
and sure enough the zoom gets longer at maximum zoom. The OM 75-150 f4 on the
other hand stays the same length as it is zoomed. Another characteristic of
the f/3.6 is that even at maximum aperture setting the diaphragm stops down
slightly during exposure so DOF will change slightly. I have not checked how
this is affected by focal length setting but this is probably just related to
keeping the max f/stop constant and I think this has been discussed on list
previously.
I don't know how the other zooms in this class vary in length, with
focal length setting but would be interested to hear.
Tim Hughes
>>Hi100@xxxxxxx<<
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