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[OM] ( OM ) Was scales in ft / m - AND d-o-f !!

Subject: [OM] ( OM ) Was scales in ft / m - AND d-o-f !!
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
Date: Thu, 3 Oct 2002 16:25:47 +1200
Hi,

That little business is over; had an appointment to revise my will - must 
make sure all the little Zuikos and OMs got to a good home when I go ...

Benson wrote
> > You can buy a lens reversing adapter, so you don't have to hold the
> > lens.  I have one, but I have never used it.  It mounts in place of the
> > lens, and the lens screws onto the adapter using the filter threads.

John Shaw's book on macrophotography covers this stuff. (Close-ups / 
Closeup photography in Nature?)  I took his advice and bought  these Hama 
accessories for OM about 20 years ago; 
stop-down ring (for reversed lenses), 
reversing ring, and 
male/male threaded ring for mounting lenses front element to front element.

Haven't used them for a while since I got closeup tubes and now a macro.

Don't overlook the screw-in auxiliary lenses (49mm and 55mm ) that screw 
on the front to give macro. They are a nice compact means of getting macro 
performance out of a standard lens.

DOF.

I don't know how much notice one should take of the DOF scales engraved 
on lens barrels, but this is what some of my lenses have. Because this 
thread came out of a remark I made about the Zuiko 100/2, these are all 
lenses set at 100mm focal length. 

F stop 22, one end of the line on infinity.
The other line fell on the following distance (metres)
100/2           10
100/2.8         7.5
35~105          4.75 (this was difficult to be sure as there is no f/22 line on 
this 
lens, but if there were, judging from the spacing of the other lines, that's 
where it would be.

F stop 16, one line on infinity

100/2           14.6 (difficult to be sure - about 48 ft - doesn't have line 
for f/16) 
100/2.8         8.5  (difficult to be sure -  no f/16 line)
35~105          8

The 100~200, and 75~150 zooms do not have DOF lines so I could not take 
a reading from them.

Here are some on-line refs.

http://fox.nstn.ca/~hmmerk/DOFR.html
http://www.dof.pcraft.com/dof.html

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0013uk  
(Find the following quote)
" Contrary to popular belief not all lenses with the same focal length produce 
the same depth of field at the same aperture! " ( Dr Kornelius J. Fleischer )

Cheers, Brian

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