At 14:39 11/21/99 , Ron & Mary Spolarich wrote:
>Goin' to school! <g> Thanks for the great explanation Chuck. Though I've
A couple things Chuck left out:
1. Extension tubes are generally thought to be better than using screw-on
close-up lenses on the lens filter ring, but lesser than a macro lens which
has optics designed for extremely close focus. Tubes do not add any glass
to the light path. Screw-on close-up lenses do, and you are at the mercy
of how good (or poor) they are.
2. Close-up lenses screwed onto the filter ring will not change exposure
settings, but an extension tube will! There are tables that show the
exposure adjustment required if you ever use tubes on a *non-TTL* metered
camera. However, TTL metering compensates for it just as it does for
filters. Just remember with an extension tube on you do lose some light,
the longer the tube, the more light lost. This might affect choice in film
speed. Kodak's Pocket Photoguide (the little pocket bible many photogs
have in the bag; used to be called the Master Photoguide) has tables in it
about the effect of tube extensions on exposure.
-- John
(who hasn't come up with a story good enough to ustify the cost of a macro
lens to his other half yet!)
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