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  1. #61
    markbarendt's Avatar
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    Quote Originally Posted by Xmas View Post
    Sorry shadows are not important if you are shooting slides.
    Well, I wouldn't put it that absolutely. I don't think that Dunn & Wakefield or others say that shadows aren't important.

    What I might suggest is that with slides, that there are physical limits to what can be in the final artifact and that "we" need to decide what is most important.

    The testing Dunn & Wakefield used does show that most people find mid-tones and highlights more important but we do well to remember that we don't have to conform.
    Mark Barendt, Beaverton, OR

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

  2. #62

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    Quote Originally Posted by markbarendt View Post
    Well, I wouldn't put it that absolutely. I don't think that Dunn & Wakefield or others say that shadows aren't important.

    What I might suggest is that with slides, that there are physical limits to what can be in the final artifact and that "we" need to decide what is most important.

    The testing Dunn & Wakefield used does show that most people find mid-tones and highlights more important but we do well to remember that we don't have to conform.
    Well ok I'll give you subjective but I've never had a bride who liked her wedding dress other then right on the edge of burnt out on the projector screen.

    They never liked the 1/2 stop bracket if it was darker.

    Kchrome 25 was nice film.

    The grooms never minded or never said.

  3. #63

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    Quote Originally Posted by Doremus Scudder View Post
    Stephen,

    Obviously I'm working from an over-simplified model and using the terminology imprecisely...

    But, for the sake of clarification, when I develop, say N-2 in order to accommodate a rather high subject brightness range, am I not changing the gradient and therefore the effective speed of the film? Or would you say that this is outside the parameters of ISO testing standards and simply does not apply?

    If the latter, then what would you call the E.I. I need to use for N-2, simply E.I.? Is that not somehow "film speed" as well? "Effective speed" maybe?

    ...

    And, although I'll more than grant you the point that ISO is a strict and reliable value arrived at by rigorous methods, I still find a bit of a disconnect about how it is practically applied. Certainly, you would not advocate my using the film ISO as my basis for metering for an N-2 negative... or when using a developer that is known to not deliver full ISO speed. Or would you?

    ...
    Doremus
    Well if you just increase the development time you might increase the 'ISO' speed for your developer if the fog level increases less than the image level, otherwise the speed might be static or reduce.

    All you can be sure is your mid tones separate.

    The shadows and the highlights may be in toes and shoulders respectively.

    You need to pick soft working developers with log fog levels to allow a wider range of 'capture' and control if your sceanes are high contrast.

    For a while Ansell used D25 and a post alkaline bath or water bath. The D25 held the highlights the post bath the shadows if you were lucky.

  4. #64
    markbarendt's Avatar
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    Quote Originally Posted by Xmas View Post
    Well ok I'll give you subjective but I've never had a bride who liked her wedding dress other then right on the edge of burnt out on the projector screen.

    They never liked the 1/2 stop bracket if it was darker.

    Kchrome 25 was nice film.

    The grooms never minded or never said.
    And this is essentially what Dunn & Wakefield found as the norm, you are not wrong there.

    Yep, IMO most grooms just seem to follow the bride's lead on the photos.
    Mark Barendt, Beaverton, OR

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

  5. #65
    Stephen Benskin's Avatar
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    This is the first part from one of the two key papers used in the decision to change the standard in 1960 and is where the Delta-X Criterion originates. C.N. Nelson and J.L. Simonds, Simple Methods for Approximating the Fractional Gradient Speeds of Photographic Materials, Journal of the Optical Society of America, V 46, N 5, May 1956.

    part 1
    Approx Fractional Gradient Speeds.pdf
    Last edited by Stephen Benskin; 05-02-2014 at 09:31 AM. Click to view previous post history.

  6. #66
    Stephen Benskin's Avatar
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    And the other, C.N. Nelson, Safety Factors in Camera Exposure, Photographic Science and Engineering, v 4, n 1, Jan-Feb 1960.

    Safety Factors pt 1.pdf

    Safety Factors pt 2.pdf

  7. #67
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    Quote Originally Posted by Xmas View Post
    Sorry shadows are not important if you are shooting slides.

    If you are shooting negatives if you get zone 1 below the halide fog it is not present so no detail.

    If zone1 is into the toe it will be more difficult to print unless you like dark prints with compressed shadows.

    Until 1960 the box speed had a safety factor of 2.5 stops, post 1960 this was reduced to 1.5.
    Bill kind of misrepresented the first excellent print test. I'll go into more details later.

    Xmas, the safety factor pre 1960 standards was 2.5 times, not stops. Afterward it was 1.2 times. You can read about it in Safety Factors in Camera Exposure that I've uploaded.

  8. #68

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    Quote Originally Posted by Stephen Benskin View Post
    Bill kind of misrepresented the first excellent print test. I'll go into more details later.

    Xmas, the safety factor pre 1960 standards was 2.5 times, not stops. Afterward it was 1.2 times. You can read about it in Safety Factors in Camera Exposure that I've uploaded.
    Hi Stephen

    Thanks, so in round terms there is not a safety factor in the ISO any more, or maybe 1/3 of a stop, given the ISO quantization.

    Noel

  9. #69
    Stephen Benskin's Avatar
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    Quote Originally Posted by Xmas View Post
    Hi Stephen

    Thanks, so in round terms there is not a safety factor in the ISO any more, or maybe 1/3 of a stop, given the ISO quantization.

    Noel
    Pretty much. The third of a stop basically comes from factoring flare into the exposure. It's easy to think that the 1/3 stop comes from the speed equation being 0.80 / Hm instead of 1 / Hm, but it doesn't. This is in Safety Factors also.
    Last edited by Stephen Benskin; 05-02-2014 at 07:45 PM. Click to view previous post history.

  10. #70
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    Quote Originally Posted by markbarendt View Post
    Just for giggles can we have some context for that rating.

    Developer?
    In comparison to manufacture's specs are you using minus development, stand...?
    Are you "zoning"? If so details?
    Subject matter?
    Spot meter or incident?
    Are you using old Petzvals or newish multicoated lenses?
    Is part of that rating a safety factor?

    My intent here is not to put you on the spot c6h6o3, but to help marciofs understand how you made your choice and at least some of considerations that go into the decision.
    Developer: Harvey's 777 OR ABC Pyro OR Pyrocat HD 1.5:1:175.
    I use the Zone System. I rate sheet film at 200, but place the shadows on Zone IV. So by Adams' philosophy I'm rating at 100. I meter for roll film at 100 and take incident readings. Therefore the answer is 'both'.
    Subject matter is anything that strikes my fancy: portraits, landscapes, abstracts.
    For sheet film I use a Nikkor 210mm large format lens, or an uncoated 12" f6.3 Dagor from 1911, or a 19" APO Red Dot Artar. My rollfilm camera is a Hasselblad. (250mm Sonnar, 150mm Sonnar, 80mm Planar, 50mm Distagon). So again the answer is 'yes to both'.
    I don't know what you mean by 'safety factor'.

    My point, both here and in the post you responded to, is that your film rating is an independent variable. "Expose for the shadows". Once you do that it's development that determines everything else about your negative. The old saw is "Develop for the highlights". But I develop for highlights, overall contrast, microcontrast in the midtones, all kinds of things depending upon what kind of negative I'm after.

    So I reiterate: The correct film speed is whatever gives you sufficient shadow detail in your prints.
    Jim



 

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