T3D More macro quesions,... using slide bar

["Andrea Blair" <asblair@xxxxxxxxxxx>]

I won't have a lot of technical specs, but I can tell you what equipment 
I use and why.

>>>>Lme Kbee wrote: I have shot some cool macro stereo shots using a 
slide bar and my slr. Now that I have heard the discussion of needing 
more light with extension tubes, I have a new question.<<<<

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

Tubes do not have glass, thus add no distortion. They can also be used 
on any lens you have to allow close focusing. Nice on a wide angle or 
fisheye where you cannot put an element on the front of the lens. 
Perhaps easier to use and carry in the field than bellows? They do, 
however, cut down on the light reaching the film, requiring more stops.

Diopters work well and are available starting at about $20 a set. They 
don't take away any light, but every time you add glass, you decrease 
the quality of the final image. 2-element close-up lenses are a better 
quality that diopters, but cost more. They are nice for converting zoom 
lenses to close-focusing lenses, but I don't think they were designed to 
stack on fixed lenses, such as a macro lens. Greg has a nice listing of 
them on his web page. Seems the 6Ts have dropped in price since I bought 
mine.

I also have another alternative. I have a nifty item from Vivitar that 
is a macro focusing doubler. It is a doubler, and, because it focuses, 
functions like tubes where you can vary the distance of the lens to the 
camera body. It's actually a great little piece and saves on space. A 
50mm lens becomes a 100mm distant AND macro lens! It works on any lens. 
I have used this a lot. I recently used it as a doubler at a football 
game. I was on the forth level (top) and used it on my 70-210 and got 
some fairly decent shots. The meter functioned properly so auto 
exposures were correct. I have used this with my 100mm macro lens before 
I got the tubes with good results.

>>>>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.<<<<

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

I prefer extension tubes since I already use a 100mm macro lens. I don't 
like to keep stacking glass. Something to consider is to get a true 
macro lens, which is a flat field lens - i.e., everything is sharp 
corner to corner. Used for copy work on stamps and such where everything 
must be sharp. 

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

Not hard at all. My 1:1 100mm macro goes to f32, which is what it is set 
at most of the time for my macro work. One of my zooms is f32 as well 
(maybe the 28-105?). I have just starting using my PZ-1p recently. Up 
until then I used my SF-1 (it died a few months ago). All of my lenses 
are autofocus, but I switch to manual focus for close-up work and 
usually work in aperture priority. The SF-1 gave me excellent results in 
this mode. I also have a K-1000, and all of my autofocus lenses will fit 
and work on this body, but they become manual focus lenses. Pentax is 
the only 35mm system that I know of that is truely 100% interchangeable 
between all of their PK bodies and lenses. I heard Nikon also did this, 
but someone said there are a few combinations that can't be used.

I also use a macro focusing rail. Not sure if this is what you are using 
too. The fine tuning of both horizonal and front to back has been 
invaluable. It is sturdy and can be used in the field. I have a Slik 
tripod with the Pistol Grip ballhead. I find this easier than a pan head 
to make quick adjustments.

Hope this helps.

Andrea

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