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Re: [OM] A question about bulk loading film & MLU

Subject: Re: [OM] A question about bulk loading film & MLU
From: "John Petrush" <jpetrush@xxxxxxxxx>
Date: Thu, 5 Mar 1998 16:24:38 -0500
Dr. Matthew J. Cordery <cordery1@xxxxxxxx> wrote:


>(1) Anyone have experience doing bulk loading? I havea bulk loader but no
>darkroom access (yet...hopehopepraypray). Anyone out there do this on a
>regular basis with a changing bag or some sort of beast? Problems (light,
>dust)?

I've did bulk loading quite seriously once upon a time.  Back then I did not
have a darkroom, but I could make a coat closet dark.  I've also used a
changing bag, same basic procedure.  If you are going to do this, buy good
cassettes and take care of them.  Mark how many times you use them and be
prepared to replace them every 5-8 loads.  Dust and grit tends to get in the
light trap fuzz and scratch the film.  Not good.  Be meticulous about
labeling.  I'll never forget the day I mistook a roll of E-6 film and
processed it in C-41 chemicals.

For what its worth, I stopped doing bulk loading after a while.  The
economics aren't all that attractive and it got to be a pain in the rear.
Many labs will not accept bulk loaded cassettes.  This greatly restricts
your processing options, especailly when traveling.
>
>(2) Currently, I am contemplating getting a new camera body. I'd like to
know
>if anyone has done any testing to see how important a mirror lock-up is on
>the OM line. Is the lack of it terribly noticeable when you blow up a
negative?
>Any help greatly appreciated.

I have done several tests on mirror lockup using a tripod mounted OM-1n.  At
focal lengths less than 300mm, or shutter speeds faster than 1/60 sec, I
could not see any difference in sharpness.  I did see differences at longer
focal lengths only if the shutter speed was in the 1/8 to 1/30 range.
Slower than 1/8 didn't seem to matter.  When I scaled this up to my
telescope (fl=2800mm) the same pattern was repeated, except the slower
ranged pushed down to 1/2 sec, probably due to the dampening differences in
the telescope's mounting.

What this means to me in practical application is for long astro exposures
(30-60 minutes), I can leave the mirror alone.  Same applies to solar
imaging where 1/500 sec seems about right.  However, for lunar work and
planetary imaging, mirror lockup helps considerably because the shutter
speed range is around 1/15th sec, plus/minus a stop.  For "normal"
photography, I don't bother with the mirror lockup but rather depend on a
tripod for sharpness.




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