reciprocity failure: B&W versus colour

Discussion in 'Exposure Discussion' started by kraker, Feb 26, 2007.

  1. kraker

    kraker Subscriber

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    I've just made my first steps into pinhole photography. Reciprocity failure (or Schwarzschild effect) is something you don't encounter every day in "normal" photography, but it's omnipresent in pinhole photography.

    So, I started comparing some data sheets of the films I use most and I found that for black and white film (which is 90-95% of what I shoot), the reciprocity law breaks much sooner than for colour (neg or slide) film.

    Case in point: Ilford HP5+, start compensating from 1/2 second; at 5 seconds, it's already more than 1 stop. Delta 100, same story.
    On the colour side there's Fuji Provia 100F (slide): no compensation up to 128 seconds; Agfa Optima 100 (neg): +1/2 stop after 10 seconds, +3/2 stop after 100 seconds.

    My question is: why does B&W film require more & earlier compensation for reciprocity law failure than colour film? :confused:

    My first guess was that things would be the other way around: colour film will need more compensation, there's 3 different layers, they all react differently to light, you'll not only need to compensate for reciprocity failure, but also for difference in reciprocity failure for the different colour layers. In B&W, there's only one layer, no difficulty to get and keep the colour right, etc.

    I'm just curious... Can anybody shed some light on this? (PE, maybe?)
     
  2. kraker

    kraker Subscriber

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    Nobody? :sad:

    Anyway, I've mentioned this to a fellow photographer who happens to be a Fuji-fan. Maybe it's just my "limited selection" of films that leads me to believe that reciprocity failure occurs sooner in B&W than in colour emulsions.

    "Look at Fuji Acros 100", he said. No correction below 120 seconds, +1/2 stop between 120 and 1000 seconds.

    Okay, so maybe I was seeing ghosts. But I want to use Ilford film! :D Fuji Acros 100 seems less of a hassle, though, for long exposures...

    Didn't look at Kodak or Rollei or Adox or what-have-you-not yet, though.

    It also seems a bit strange that the reciprocity curve for the "classic" Ilford films and the Delta range is exactly the same (Simon?). Maybe I shouldn't take these curves as the truth, and just do some experiments.
     
  3. Mick Fagan

    Mick Fagan Subscriber

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    I first noticed that there was a real difference with colour film when Kodak Ektar 25 professional came out, this was a colour negative film.

    IIRC there was no change required down to 10 seconds.

    The Fuji Reala that I have used since it came out, has a change required from 1 second (I think)

    Currently I have Tmax 100 4x5 film which is a 1991 expiry, it has no problems until you get to 1 second when you need to allow for reciprocity.

    The FP4+ 4x5 film that I opened two weeks ago has virtually identical reciprocity requirements of the Tmax 100.

    I too noted that Ilford films, both the conventional and modern flat technology, were similar in their reciprocity characteristics.

    However Kodak's Tmax and TRI-X have virtually identical reciprocity requirements to the Ilford film, so I don't see anything problematic with the Ilford films.

    I have recently metered a moonlit scene that suggested 120 minutes at f/11 for the Tmax film. With reciprocity allowances of about 3 stops required, I juggled a hat over the lens whenever a car came along, I got the shot, then went to bed.

    Generally I have found that you lose shadow detail, no matter what you do. In a nocturnal exposure, this takes on a real interesting meaning.

    Mick.
     
  4. kraker

    kraker Subscriber

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    Hi Mick, thanks for sharing your findings;

    So *that's* why a photographer needs a hat! :tongue:

    That's is a valuable remark: look at it artistically, not too scientifically. :wink:
     
  5. Lee Shively

    Lee Shively Member

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    With color film you also can get a color shift which needs filtration to correct, so color can be more complicated in reciprocity compensation than black and white. I haven't shot large format color in years, but I remember using Ektachrome 64 in 4x5 and having to filter the hell out of it with different strengths of magenta, depending on the length of the exposure. I presume the current color transparency films have improved in the respect.

    With black and white, I generally trust the film's latitude and just bracket in half stops up to two stops over the meter reading. That always gets at least one good printable negative.
     
  6. eddie gunks

    eddie gunks Member

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    i can not explain why this is but i like it. i too shoot pinhole. i have since moved from foma100 to tmax100 becuase tmax is so much "faster" than foma. what took me about 3-5 min takes the tmax like 40 sec! thats fast! acros and tmax seem to be the fastest. i find FP4 to be much much slower than tmax. i shoot fp4 the same as i do the foma and it comes out perfect.

    i enjoy shooting color neg and slide film with the poinhole because it is so fast. i mostly shoot NPS 160 rate it at 50 and do no further compensation. works great everytime.

    FYI check out http://www.pinhole.cz/en/pinholedesigner/ it give great reciprocity calc for most B&W films. as well as lots of great pinhole related info.


    eddie
     
  7. eddie gunks

    eddie gunks Member

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    some pinhole photos below. slide, neg, and B&W
     
  8. Rich Ullsmith

    Rich Ullsmith Subscriber

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    Eddie, I agree about the FP4, I didn't notice much difference between it and Delta 100 in adjusting. I loved the Acros 100; with a red 25 filter out in the sun, exposures were around 90s. However, I have yet to find an Acros 100 source (4X5) that is not in the quick-load packs, which cost about two and a half clams apiece! Now I got a box of tmax100 but the sun hasn't shown here in about four months, so I've yet to try it.
     
  9. Michel Hardy-Vallée

    Michel Hardy-Vallée Membership Council Council

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    Your sample is too limited for the conclusion you draw: Ilford films are not renowned for their reciprocity behaviour, even the modern Deltas. In comparison, the Kodak T-Max and Fuji Neopan films have way better reciprocity. Fuji claims no adjustement below 120s for Acros 100!

    With B&W films, you have to bear in mind that the current market is split between "classic" and "new" technology. Classic films like FP4+, HP5+, Tri-X, Plus-X, do not in general have as good a reciprocity as New tech films like T-MAX etc.

    Now, most color films currently in production (with the exception of Kodachrome) use grains similar or identical to the New Tech films. Ektachrome uses t-grains, like t-max does. Provia uses sigma-grains, like Acros. As these grains have better reciprocity characteristics, so do the color films using them. Provia has about the same reciprocity characteristics than Acros does.
     
    Last edited by a moderator: Mar 8, 2007
  10. kraker

    kraker Subscriber

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    Yes, I noticed that already, Acros 100 sounds very nice in that respect :wink:

    Still, I had expected more of the Ilford Delta line, which is also "New tech".

    Thanks for this clarification.
     
  11. Michel Hardy-Vallée

    Michel Hardy-Vallée Membership Council Council

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    My pleasure. I too am wondering why Ilford did not try to cash in on reciprocity with the Deltas.
     
  12. colrehogan

    colrehogan Member

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    Rich,
    For LF non-Quick Load Acros 100, go here:
    http://www.unicircuits.com/shop/

    Yes, it's in Japan, but as far as I know, it's the only place you'll get it in loose sheets.

    Regards,
    Diane