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Re[2]: [OM] ISO extension tubes

Subject: Re[2]: [OM] ISO extension tubes
From: JIM_TEO@xxxxxxxxxxxxx
Date: Mon, 16 Nov 1998 11:42:22 +0800
     Can anyone advise the exposure for using revesing lens?
     
     
     
     jim


I just happened to be visiting the KEH
 http://www.keh.com/catalog/text/Om.html ) when this message arrived.  The
auto-tube 65-116 ranges from US$126 - 179 (without and with tripod mount, EX 
condition).  A full set of auto extension tubes, 7mm, 14, and 25mm, in EX+ 
condition is UD$139.  Individual extension tubes were listed for US$20-30, 
but they are not the auto variety.  Also, there was one 50mm f/3.5 macro, 
EX+ condition, listed for UD$235.
     
Non-macro lenses will work on extension devices (bellows, auto-tube or 
extension tubes).  I did close-up photo for years with 50mm and 135mm 
"normal" lenses and a third party bellows.  Not optimal, but I learned a 
*lot* about "seeing small" in the process.  Macro lenses are optimized for a 
certain range of magnification, e.g. the 80mm macro is best at 1:1.
However, a standard 50mm f/1.8, with a set of extension tubes, opens the 
door to a very interesting and exciting world of macro work.  A true macro 
lens will provide better technical results, true, but also has its own set 
of compromises such as cost, speed, size/weight and general utility.
     
In the Zuiko family, the 50mm macros (f/2 and f/3.5) and the 90mm f/2 can be 
attached directly to an OM body.  The auto-20mm f/2, 38mm f/2.8, 80mm f/4 
and 135mm f/4.5 macros are all supposed to be used with some form of 
extension.  I know for sure the 135mm will not even fit, the rear element 
protrudes too far rearward.  I believe the same is true for the auto-80mm 
version - it looks like the preset one will actually fit, but I've never 
tried it.  The older style 20mm and 38mm macros have a screw thread and 
require and adapter (OM-PMoB??) to mate to the OM body.  These are preset 
lenses and are quite good.  Just remember they are useless without the 
adapter.
     
IMHO, you will get better results with a normal lens with a reversing ring 
and extension than with a normal lens and close-up lens attachments. 
However, you again have trade-offs to make.  With extension, there is an 
exposure compensation required, effectively reducing the lens speed due to 
light falloff from the extension.  With close-up lenses, the true lens speed 
is retained.  With the reversing ring, all body-to-lens automation is lost, 
leaving you with effectively a preset lens arrangement.  My extension tubes 
are the non-auto style, but that has no effect on the final image.  I don't 
mind the manual preset for macro anyway.  It is my intent to slow down and 
"see".
     
Sorry, I seen to have rambled.........
     
John P
______________________________________
there is no "never" - just long periods of "not yet".
     
     
Red Rover <red_rover@xxxxxxxxxxxxx> wrote:
     
     
>    How much do the auto tubes go for? And where can I find them (anyone 
>here maybe?) ? Also, are they only supposed to be used with the macro 
>lenses? I'm saving up for a 50 3.5 but would like to do some closeup work 
in
>the meantime. Would rather not have to resort to lens closeup attachments.
     
     
     
     
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