T3D Re: More macro quesions,... using slide bar

[erker@xxxxxxxxxxxxxx (Greg Erker)]

>What are the pros and cons of using extension tubes, and also the same
>for using plus lenses instead.

  Other's have answered this question. I will
add that achromatic (2 element) closeup lenses
perform much better than the cheaper single element
ones. I have a table on my web page that shows all
the currently available Achromatic CU lenses (they
start at about $30 for one).
http://www.angelfire.com/ca/erker

>ALso, how hard (or expensive) would it be to find a pentax K mount
>lense that has an fstop beyond f22?

  I have a Pentax-M 135mm f3.5 lens that goes
to f32. But if you use it and then view your
slides with a viewer with 40-50mm focal length
you will have a fairly squashed image (the
opposite of stretch).

Greg E.



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