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  1. #21
    ath
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    Acros is not really orthopan. Fuji states this in the datasheet but in reality it behaves more like a panchromatic film. EFKE25 and 50 are orthopancromatic and show visibly darker reds.
    Last edited by ath; 08-31-2011 at 02:35 AM. Click to view previous post history.
    Regards,
    Andreas

  2. #22

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    Just look at the spectral sensitivity diagram for ACROS. It IS orthopan. The curve drops dramatically
    mid-red. A simple test for this is to take a deep red filter like a 29 and see what happens. It acts like a
    sharp cutoff filter. You'll chop at least an entire Zone out of the shadows, and more exposure compensation won't salvage anything down there. With a medium red 25 you get a normal response with the ordinary 3-stop exposure factor. Also look at the rendition of greens. Much different than a
    pan film. If you add a yellow-green filter to the already orthopan response, yellow-greens in nature will
    come out almost white, way above the response of typical pan films. I've done many of these tests.
    ACROS is one of my favorite 4x5 films in the mtns because things take on a much more luminous natural
    quality.

  3. #23
    ath
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    Quote Originally Posted by DREW WILEY View Post
    Just look at the spectral sensitivity diagram for ACROS. It IS orthopan. The curve drops dramatically
    mid-red.
    Well, I DID look at the spectral sensitivity curves. Published curves are hard to interpret because nearly always vital information is missing (i.e. the way they were derived). Acros drops at ca. 640nm (-0,5 stops) , TMAX100 at ca. 640 to 650nm, depending on the graph you choose, EFKE25 at 625nm. Now, which one to call panchromatic and which one not?

    Quote Originally Posted by DREW WILEY View Post
    A simple test for this is to take a deep red filter like a 29 and see what happens. It acts like a
    sharp cutoff filter. You'll chop at least an entire Zone out of the shadows, and more exposure compensation won't salvage anything down there.
    My experience is completely different. With a Red 29 Acros behaves nearly identical to Delta 100, same filter factor, same darkening of sky and so on. Probably because sensitivity of Delta 100 also drops at 640nm.

    The character of a film is much more than the label "orthopanchromatic".
    Regards,
    Andreas

  4. #24
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    Quote Originally Posted by DREW WILEY View Post
    ACROS is orthopan, not panchromatic. It has a different look from ordinary panchromatic films, which would need a light yellow-green filter to achieve the same effect.
    Incorrect.

    Fuji's data sheet says orthopanchromatic. It's something in between full panchromatic and orthochromatic.
    The curve in their data sheet shows response to 640nm. Incidentally, that is as far as TMax 400 goes as well.
    "Often moments come looking for us". - Robert Frank

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  5. #25

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    Very minor differences in the shape of the cutoff can make a huge difference in practice. TMY and Delta
    are not similar to ACROS at all in their red response. Like I said, just try working with a true red 29 filter
    and this becomes apparent. But ACROS isn't quite the same as Efke 25. Each of these films has its own
    personality. But if you don't understand the basic category of sensitivity, you can get into trouble.
    Probably most people don't note the distinction because use of a 25 med red filter is much more common than a 29. But try a hard green filter on foliage. An orthopan film will look virtually bleached out in comparison to a true panchromatic. I've made that mistake myself. Up in the high country, the orthopans give an entirely different look, much more airy, buoyant, but not like a true ortho either.

  6. #26

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    To my experience Acros 100 is much nearer to panchromatic than to orthopanchromatic.
    Or in other words it's a "very very light orthopanchromatic".
    Real orthopanchromatic films are
    - Efke 25 / Adox CHS 25
    - Adox CMS 20
    - Rollei Retro 100 Tonal.

  7. #27

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    Are some of you guys winging this, or have you done actual objective tests under a variety of circumstances and plotted them with a densitometer like I have? But I will admit that "orthopan" is a category, with slight distinctions between specific films, and that ACROS is a bit less ortho than Efke 25for example. Still, I've got a helluva lot of experience with this particular film, especially at high altitude,
    and my results are very very predictable because I undertand how it differs from typical pan films.

  8. #28

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    Spectral response aside, a unique characteristic of Acros is its curve shape in areas of high exposure (above zone VIII in zone system parlance), where local contrast is actually highest and stays that way up to around zone XII or even XIII, with a more abrupt shouldering thereafter. This general curve shape with a contrast bump beginning around zone VIII exists even with severely contracted development. This is quite different than most other current films where the curve stays pretty straight with a more gradual shouldering in the highlights. Acros's high highlight contrast can be either a favourable or unfavourable quality depending on the situation, but worth noting in any case.

  9. #29

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    I would go with T-Max 400 with T-Max devepoler.

    Jeff

  10. #30

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    Michael - I've never had a problem with ACROS shouldering off, even in very contrasty mtn scenes with snow and glacial polish on granite etc. But I develop it in PMK pyro, which makes printing the highlts very
    practical. But this also allows me to bring the deep shadows up onto a straighter section of the curve by using ASA 50. A wonderful film when speed isn't the priority. Jeff- TMY is distinctly grainier, at least if you print a 20X24 from 4x5, for example, has a different spectral sensitivity (as noted), different recip
    characteristics, etc - a completely different animal, though one of my favorite films too.

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