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[OM] Kodachrome 25 test, including reflectivity

Subject: [OM] Kodachrome 25 test, including reflectivity
From: Frank Ernens <fgernens@xxxxxxxxxxxxxxx>
Date: Wed, 16 Aug 2000 07:37:52 +1000
(LONG POST)

As usual, this is one amateur's *subjective* test. Use at your
own risk, and meant mainly as a starting point for discussion and
other peoples' tests.

This roll was from batch 152 233, expiring 10/2000, made
in England.

1. Reflectivity

As for Elitechrome 100, four exposures of a Kodak grey card were
made, using the OM-2SP and Tamron 90mm f/2.5:

  i. 1/250 f/4 auto
  ii. 1/250 f/4 manual/spot
  iii. 1/15 f/11 auto
  iv. f/4 auto TTL flash
  
Exposures (i) and (ii) were correct and within 1/5 stop of each
other. Exposures (iii) and (iv) were both about 1/3 of a stop
overexposed; exposure (iv) had the usual blue colour cast from
the 5800K T20. This indicates that this roll of Kodachrome 25
had a reflectivity close to what the OM's off-the-film system
was expecting, although not exactly.

As before, if others can repeat this test the results become
more believable. In particular, Kodak have still not answered
me as to whether they QA for film reflectance, so what was true
for this batch might not be true for others.

2. Colour test

Photos of the same colour chart that Provia F botched so badly
were made at the correct exposure and at one stop overexposed.
Sage greens and similar colours were rendered more as puce.
This is consistent with the behaviour of Kodachrome 64 I have
seen so often, with saltbush and dried gum leaves (both close
to sage green) coming out as pink. All the other colours were
very accurate, even with the +1 exposure, although of course
they were desaturated by 1 stop (good gradation).

In use (landscapes, cityscapes and flowers), the film is noticeably
more saturated than Kodachrome 64. It's probably this one and not
the 64 that National Geographic used to use. I got some early
morning shots with that wonderful Kodachrome "glow", and the
extra saturation helped that. I think the film is so good at
this because the colours remain true (albeit desaturated) with
overexposure. Blue skies were... very blue, but not cheesy as
Velvia would have rendered them. Furthermore, the data sheet
suggests Kodachrome 25 won't burn out the highlights as quickly
as Kodachrome 64, and there does seem to be more detail there
than I would expect with 64.

3. Contrast range

About as expected. Less capable than Elitechrome 100, more
than Velvia. The data sheet says it is slightly contrastier
than Kodachrome 64, but also that the red blocks up first
instead of the green. I found it reasonably forgiving, but
didn't shoot in extreme conditions.

Note that, as I live in a sunny country, I am looking for
low contrast. Cold dwellers might want the opposite.

4. Reciprocity

Reciprocity failure occurs even earlier than Kodak claim (+1/2
stop at 1 sec.) I think the film was 1 stop down at 1/2 second.
Not the film for sunsets, unless you like that daggy 60s orange
on black Kodachrome effect. Rather a disappointment, as I'd
hoped the 25 would have the 64's colours without its dreadful
low-light performance.

I have suspected for a while that Kodachrome 64's reciprocity
is worse than claimed, and that the error inherent in the OM's
off-the-film measuring is partly compensating for it. Kodak
say to test each batch separately, somewhat impractical advice
given the turnaround for processing.

5. Resolution and grain

No enlargements yet, but under the loupe on a light table it
looks excellent, in the same class as Velvia/Provia F/Kodachrome 64/
Elitechrome 100. Under the microscope, the grain is very noticeable -
you can see the clumps, but they are smaller and more regular in shape
than that of the other films.

6. Processing

The quality was excellent, but 2 1/2 weeks including 2-4 days postage
is too slow for me. Bear in mind that it was not sent off
at a time when there would be a crush at the lab (school holidays
etc.). Normal time for Kodachrome 64 is 6-9 days from the same
lab. This is the "slow" Kodachrome in more than one sense!

7. General usefulness

ISO 25 presents a problem with the OM-2 and OM-2SP because
you don't have the full range of exposure compensation.

For landscape work, good for early morning "magic light",
but hopeless in low light levels due to early reciprocity
failure. You also need a still day because of the longish
exposures. For cityscapes, outstanding, but I prefer an
ISO 100 film because with that I can stop down to f/5.6
(where both the 35 shift and the 24/2.8 start performing
well) and still hand-hold. If you like flashed flower shots
with a black background, the slow speed is an advantage.

In summary, a special-purpose film, but a very good one.

** Copyright (C) Frank Ernens, 2000. May be reproduced
without restriction, but only in electronic form, not for
profit and must be acknowledged.

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