T3D Macro Comments

[Bob_Maxey@xxxxxxxxxxxx]

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

Supplementary lenses do not require additional light. However, there can be
a loss of quality, depending upon who you talk to. They can be expensive as
well, depending upon the manufacturer. The advantaghe for most is they are
readily available, can be combined, cause no light loss and do a fairly
good job.

>>Some one had asked what was the size of subjects I wanted to shoot,
>>well......  Something that is 3 inches tall, and all the way down to
>>something that is only a half inch tall.

Consider using a Bellows rather than extension tubes. With tubes, you only
have a few fixed options for varying the extension. A Bellows is continuous
within a range . I never use tubes - always the Bellows.

>>So is the better thing with extension tubes that you get a sharper
>>image, and with the plus lenses you can have more light?

Yes and no. Supplementary lenses do not increase the light levels, they
simply do not require any adjustments and you do not loose any light. With
Extension tubes or a Bellows, there is no loss in quality as nothing has
been added that change any of the lens characteristics, but you do loose
light. something to be seriously considered if your subjects move. Expect a
lot of multi second exposures - especially if you are using a good film
like Kodachrome 25 or 64.

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

I would guess they are available, but probably in longer focal lengths than
you really want
to use. I am not a Pentax person so I really do not know what is available.
I would guess that Pentax offers / offered a Macro Lens and you might look
for one.. Remember that as you go closer with a Bellows, you loose light.
Do not worry about formulas, they are readily available and probably come
with the instructions to the Bellows you choose to use.  One thing to watch
out for is allowing time for the setup to settle between exposures. You
also need a sturdy tripod because even tiny vobrations  anywhere in the
setup will be seen in the photographs. This is especially true with stereo
work. Good luck.

FYI: My preferred setup for  35 MM macro work is a Leica Rangefinder
camera, a Visoflex and a Bellows. For larger format, I use a Hasselblad and
Bellows.

RM



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