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  1. #21

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    His handle is the molecular formula for Pyrogallol. I'm gonna guess ABC. That's one stop. Zones, that's another 2/3 stop. Close enough.

  2. #22
    markbarendt's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    His handle is the molecular formula for Pyrogallol. I'm gonna guess ABC. That's one stop. Zones, that's another 2/3 stop. Close enough.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  3. #23
    Sirius Glass's Avatar
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    Quote Originally Posted by cliveh View Post
    Shoot at box speed and develop to your own requirements.
    +1
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  4. #24

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    Some here still haven't figured out that ISO testing is based on one particular development regime using a standard developer and a contrast index that likely does not relate to either of those things for most of us. ISO speed is similar to EPA mileage estimates for new cars: a good basis of comparison but your mileage may vary.

    The issue is further clouded by the practice of some manufacturers to label the film at a different "Box Speed" than the ISO speed. I find this deceptive and poor marketing in the long-term, since many will simply have poor results since their expectations have been falsely raised.

    Personal EI is based on the amount of shadow detail that each individual photographer finds necessary/acceptable for the kind of work s/he is doing. This includes personal and artistic decisions regarding developer, contrast, etc., etc. This includes all kinds of "pushing" and Zone Systems, etc., etc.

    Kodak's old recommendations still hold: If your negatives have too little shadow detail, increase the effective film speed. Too much shadow detail (i.e., more than you need)? You are overexposing and can get away with less, thus giving you faster shutter speeds/smaller apertures.

    Overall contrast is similar: Consistently too contrasty? Reduce development time. To flat? Increase. Plus, learn to base development on scene contrast.

    Best,

    Doremus

  5. #25
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    Quote Originally Posted by Doremus Scudder View Post

    Kodak's old recommendations still hold: If your negatives have too little shadow detail, increase the effective film speed. Too much shadow detail (i.e., more than you need)? You are overexposing and can get away with less, thus giving you faster shutter speeds/smaller apertures.

    Overall contrast is similar: Consistently too contrasty? Reduce development time. To flat? Increase. Plus, learn to base development on scene contrast.

    Best,

    Doremus
    Other way round you mean increase the exposure by decreasing the Effective film speed (EI - exposure index) - to give better shadow detail.

    Ian

  6. #26

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    The ISO for many films are calculated at a contrast index in the 60's. I print with a condenser enlarger and prefer a negative with a much lower CI. As development times are shortened shadow detail can disappear very quickly which I offset with a lower EI. Testing for ISO at a CI of .45 would make film manufacturers very unhappy. The ISO 400 calculated at a CI of .62 would not hold up at the lower CI. Would you prefer to market the same film at 400 or 250 if you were a manufacturer?

  7. #27
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    The digital truth timings should take account of the film/developer combo to get a normal exposure for the nominal ISO setting.

    I haven't used Rodinal in a while but supposedly, you can lose up to a stop of film speed with limited pushability. Therefore some people overexpose the film to compensate.

    personally, i rely more on manufacturer data sheets, to set a starting point for times. Then you have to dial it in to your shooting style and preferences.

  8. #28
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    Quote Originally Posted by Rick Jones View Post
    The ISO for many films are calculated at a contrast index in the 60's. I print with a condenser enlarger and prefer a negative with a much lower CI. As development times are shortened shadow detail can disappear very quickly which I offset with a lower EI. Testing for ISO at a CI of .45 would make film manufacturers very unhappy. The ISO 400 calculated at a CI of .62 would not hold up at the lower CI. Would you prefer to market the same film at 400 or 250 if you were a manufacturer?
    Being able to choose a personal CI and EI is a wonderful thing. I develop and shoot for the specific CI and EI I like too.

    The ISO number though is different. The ISO standard is a very specific and measurable and manufactures have to disclose it. Marketing and using a film in the real world is a different animal yet again.

    For example this from the Ilford Delta 3200 data sheet:

    DELTA 3200 Professional has an ISO speed rating of ISO 1000/31º (1000ASA, 31DIN) to daylight. The ISO speed rating was measured using ILFORD ID-11 developer at 20°C/68ºF with intermittent agitation in a spiral tank.

    It should be noted that the exposure index (EI) range recommended for DELTA 3200 Professional is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #29

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    Interesting how almost "anti-box speed" people are. Even granting people are disinterested in the basis for ISO speeds (since it seems people tend to view it as some laboratory thing of little practical use in the making of real art, or as a marketing trick), I wonder how many of them are getting what they think they are getting when it comes to the various methods of establishing a personal EI.

  10. #30
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    I should have mentioned that my normal/target EI is typically the ISO speed.

    I do agree Michael. Several of the biggest leaps forward in my skills and understanding came from settling on using box speed to shoot, standardizing on a "normal" development regime, and using incident metering as my gold standard.

    Various things drove me this direction; the standardization and latitude C-41 brought to the table, using roll film for most everything, learning that the ISO standard had it's roots in 1,000's of people judging real printed results, figuring out that Kodak, Ilford, and Fuji have really done their homework...

    When I started experimenting with the practical aspects of shooting and standardizing my B&W process based on principles C-41 taught me, I was amazed. Chasing off Ansel's ghost and unlearning the "need" to adjust development for every EI change was another major step forward. Long live VC paper.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

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