On Tue, 3 Apr 2001, Chris O'Neill wrote:
> On 3 Apr 2001, at 12:14, Ian A. Nichols wrote:
>
> (some stuff about testing focus accuracy of a 35RD rangefinder)
>
> [Snip!]
>
> > After a bit of tweaking and a few test frames, it's now much better.
>
> Explain further how you did both, please? Not that *I* am capable of
> doing either without totally screwing it up, but it sounds interesting!
OK. First the testing bit
Camera on tripod pointing at subject with vertical lines, back open,
focusing screen (I used one from a dead Pentax ME super because I happen
to have one, it's a bit smaller than Oly screens and less likely to
result in damage to one of my Oly screens if the cat knocks the whole
thing over) strapped gently across the film rails with rubber bands.
You have to make sure that the screen is resting on the inner two rails
(where the film would be) and not the outer two (which guide the film).
Also, you don't want the screen to flap about or bend inwards, so don't
have those rubber bands too tight. Best to have them over (or very near)
the film rails. Oh, and make sure the matte side of the screen is
towards the lens, the opposite of the way they go into OM bodies.
Set the rangefinder so that it thinks the lens is focused on the
subject, open shutter on B and examine focusing screen with loupe to see
if it agrees. Repeat at different subject distances to see if any
pattern emerges.
Readjusting the rangefinder: under the top cover, just below the
viewfinder window, there's an eccentric post which pushes the lever that
turns the mirror that moves the split image. Focus on the subject using
the screen, then adjust that eccentric until the rangefinder agrees.
Testing your handiwork: line up a few similar subjects at different
distances (I used a row of 7 CDs spaced evenly between 0.5 and about 2m
from the camera). Expose successive frames (using largest aperture)
focusing on each CD in turn. Develop and print (or scan) and see which
one is in focus.
It occurs to me that those of you with RDs who have expressed
disappointment with the sharpness of their negatives might like to try
this test: it could just be that you're not actually focusing where you
think you are. My RC (and my OM-1 and 4 - the 2SPs had film in them)
checked out fine.
--
________________________________________________________________________
* | |
| / | |/-\ | Ian A. Nichols |
| | | | | | http://www.chm.bris.ac.uk/~cpian/ |
| \-/| | / | i.a.nichols@xxxxxxxxxx |
| * iann@xxxxxxxxxxxxx |
------------------------------------------------------------------------
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|