At 00:45 10/6/00 , Don Gaikins asked:
[snip]
>or 28mm 1:2.8. I have seen posts on the list (and adds on eBay)
>that talk about fast and slow lenses. Could someone explain to me what
>a fast lens means? What slow lens is?
>
>I thought that the second number just meant the widest aperture that the
>
>lens could achieve. What does that have with speed?
[snip]
Welcome to Zuikoholics Anonymous.
I think the terminology comes from how fast the image will be formed on the
film with a proper exposure, that a "faster" lens allows "faster" shutter
speeds, and that it dates to a time when routine exposures were measured in
seconds, not fractions of seconds. The wider the aperture diameter, the
faster the shutter speed under the same lighting conditions, and the faster
the lens.
What constitutes a "fast" lens is relative to the focal length. An f/2.8
180mm is considered "fast," but in a 50mm it would be considered slow by
today's standards. Similarly, an f/2 28mm is "fast" but an f/2.8 "average"
and an f/3.5 "slow."
It's also relative to the film format. In medium format, very few standard
lenses (75mm or 80mm) are faster than f/2.8. In large format view cameras,
they're even slower yet.
BTW, the OM-1 is a great manual camera body! I have an OM-1n and I've
handled some of the others from its era such as the Pentax K-1000, Nikon
F-2, etc. It's small, light, well-built, very sturdy, and very reliable; a
real workhorse.
Just watch what cells you put in the OM-1. The metering will not read
accurately with the higher voltage alkaline cells (1.55V) that have
replaced the now defunct mercury PX625 (1.35V). The error can be as much
as three stops. Many cameras and light meters from its era were designed
for the mercury PX625 cell, so it's a commonly encountered problem. There
are some options to the defunct mercury cells it was designed for:
An adapter collar that allows using lower voltage hearing aid cells:
http://www.olympusguy.com/NewLArt8.htm
A solidly built MR-9 adapter that drops the voltage of silver cells:
http://www.criscam.com/
A conversion of the battery compartment and meter circuit:
http://www.zuiko.com/
(John Hermanson also sells the MR-9 adapter.)
I use the MR-9 in two different cameras and a light meter.
-- John
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