Gary Schloss quoted, wrote:
>Bradley Mabb wrote:
>
>[snip]
>> And one odd observation- I was getting a higher shutter speed through the
>> Zuiko 300 (f 4.5) than I was the Vivitar (f 4.0 at 210). A stop and a half
>> difference. Strange.
>
>Hmm, I always suspected that OEM manufacturers rate their lens' speeds
>rather conservatively, whereas the independents often play fast and loose
>with the max. aperture numbers.
Hmmm... it's my impression that the f ratio is exactly that -- a ratio of
the focal length to the focal width. It says NOTHING about actual light
gathering ability -- only about the mechanics! If fewer elements are used,
or better glass, or better coatings, a lens should be brighter than one
made with more elements, cheaper glass, cheaper coatings, etc.
A few years ago, I went shopping for compact binoculars. The difference in
brightness between binocs with identical specs is AMAZING! You can buy
10x25 binocs at K-Mart for $29.95 that have trouble discerning a crow at
noon. On the other hand, after trying out five or six pair over the course
of several hours, I'm the proud owner of Zeiss 10x25 binocs -- the only
ones in which I could read a sign INSIDE a neighboring parking garage.
My Zeiss binocs out-perform a friend's Bushnell 10x40 binocs, and weight
less than third as much!
: Jan Steinman <mailto:jans@xxxxxxxxxxx>
: 19280 Rydman Court, West Linn, OR 97068-1331 USA
: +1.503.635.3229
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