Re: Film speeds with R72

["David Lee" <koganlee@xxxxxxxxxxxxx>]

Tom,

> Anybody have any
> reccomended starting points for konica750 and maco820?
>  I am shooting a R72 ...

I recently did a comparison test with Konica 750 and Maco 820 using both a
#25 filter and an R72.

I metered with a spot meter and on a textured dark area (not green foliage).
(I closed the aperture 1.5 stops from what the reading said, or in Zone
system terms, I placed the reading on Zone III-1/2.) I should also mention
that I shot the test in open shade, as I shoot almost everything. IR works
great in open shade.

I developed the films in TMax developer, as I do all my roll film. The Maco
was at a 1:9 dilution for 15 minutes at 75 degrees in a Jobo processor. The
Konica was at 1:15 dilution for 10 minutes at 75 degrees, also in the Jobo.
(I have shot many rolls of the Konica and this processing has worked well.)
Note that the Maco takes considerably more development to get comparable
results. (For comparison, I develop TMax 100 and Ilford Pan F at 1:9
dilution for 9 minutes.)

The ASA results were substantially in agreement with those on Marco Pauck's
web site
http://www.pauck.de/marco/photo/infrared/comparison_of_films/comparison_of_f
ilms.html

Konica with #25 - ASA 6 to 12
Konica with R72 - ASA 3 to 6
Maco with #25 - ASA 12 to 25
Maco with R72 - ASA 3 to 6

Note that the Maco is about a stop faster with the #25. With a visual
comparison of the negatives the Konica at 6 and 12 are almost identical to
the Maco at 12 and 25. With the R72 they are about the same. On a visual
inspection they give the same shadow detail at the tested exposures, with
perhaps a little more IR effect in the foliage for the Maco (although this
would be subject to change with different development).

The definite conclusions which can be drawn regardless of your metering
style or the light you shoot in, is that (assuming that you want to keep the
density of the shadow detail constant):

1. With a #25 filter the Maco is twice as fast as the Konica.
2. With an R72 filter they are both the same.
3. The Konica  is twice as fast (1 stop) with a #25 as it is with an R72.
4. The Maco is 4 times as fast (2 stops) with a #25 as it is with an R72.

Another piece of useful information that I learned from this test was that I
could load the Maco in very subdued light and not get any fogging. I was in
the house with the light out, but with enough light so I could see what I
was doing and where the "start mark" was, and there is absolutely no
evidence of fogging.

By the way, I have shot the Konica extensively (almost entirely in diffuse
light with a #25 filter) and have had excellent results with it. The Maco
appears to be very similar with perhaps a bit more IR effect.

David M. Lee

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