At 11:43 PM 27/03/2002 +0000, Kierstin wrote:
>I have looked at the photo and it looks like it says 1:5.6 (does this mean
>anything?).
Yes, its aperture wide-open is F/5.6, quite slow (i.e., dark).
>wow I didn't realise that it could make so much difference. {F5.6 is
>getting slow enough to mean a rather dark and hard to focus image in the
>viewfinder}. why is this?
Again, all other things being equal, it's less expensive to build a lens with a
smaller maximum aperture. The lenses weigh less, have less glass in them and
are physically smaller than they would be otherwise. Within certain limits,
it's a function of physics -- you want a faster piece of glass, it's gotta be
bigger, heavier and (of course!) cost more. Beyond about F/5 or so, the lens
isn't capable of gathering enough light to produce a reasonably bright image in
your viewfinder, and then you have problems composing and focusing the shot.
Yet the Zuiko 300/4.5 is bright enough, and because it's got good contrast,
it's also easy to focus.
I own the Olympus Zuiko 250mm/2.0. It's an awesome lens, and exceptionally
bright in the viewfinder, but it weighs 7.7 kgs, and it looks like a cannon
mounted onto the front of your camera. It's "hand-holdable" for *short*
periods of time (or with special gun-grips that look sort of like a rifle that
you attach into the lens' tripod socket and then snug into your shoulder...).
As an approximate comparison, the Zuiko 200mm/4.0 is about one-twentieth the
cost and about one-fifteenth the weight, and is easily hand-holdable. A 5.6
Viv would *probably* be even smaller and lighter, but might be hard to use.
See if you can "try it out" first.
Garth
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