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  1. #1
    CreativeMJP's Avatar
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    Ilford Delta 100 Reciprocity Departure Chart (approximated)

    Greetings,

    I'm not sure if this is going to be useful to anyone else. But I took a detailed look at Ilford's reciprocity chart for Delta 100 and came up with the numbers seen on the attached graphic. I apologize if this post is somehow unnecessary or redundant. I'm new to APUG and film shooting in general.

    Respectfully,

    Mike Peters
    Minneapolis, MN
    Click image for larger version. 

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  2. #2
    andrew.roos's Avatar
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    Hi Mike

    Welcome to APUG and thanks for posting this.

    However note that the reciprocity failure chart that Ilford provides in the Delta 100 data sheet is not accurate. An indication of the problem is that the reciprocity failure graphs given by Ilford for FP4+, HP5+, Delta 100 and Delta 400 are identical. It is extremely unlikely that these films (which include both conventional and CCG emulsions) have identical reciprocity failure characteristics, so I expect it is sloppiness on Ilford's part copying and pasting the graphs rather than actually performing the measurements.

    Both Howard Bond and I have done independent measurements and our results are quite similar, but quite different to Ilford's data! See my post on this at http://www.apug.org/forums/forum37/1...lta-100-a.html. There is a pointer to Howard's results in one of the replies to my post.

    My "rule of thumb" based on these measurements is that no correction is required for exposure times up to 4 seconds. For exposures longer than 4 seconds, add an additional 1/3 stop of reciprocity failure correction for each stop of (metered) exposure over 4 seconds.

    Regards
    Andrew
    Last edited by andrew.roos; 01-17-2013 at 02:06 PM. Click to view previous post history.

  3. #3
    CreativeMJP's Avatar
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    Hey Andrew,

    Thanks for the correction and explanation. I will put your suggestion to good use.

    Mike

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    Richard Sintchak (rich815)'s Avatar
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    Ilford Delta 100 Reciprocity Departure Chart (approximated)

    Anytime I have to worry about reciprocity with Delta 100 I use Fuji Acros instead.
    -----------------------

    "Well, my photos are actually much better than they look..."

    Richard S.
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  5. #5
    CreativeMJP's Avatar
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    Rich815,

    I hear that Fuji Acros is wonderful film. But, how does that song go . . . "If I were a rich man . . ."

    ;-)

    Mike

  6. #6
    Richard Sintchak (rich815)'s Avatar
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    Ilford Delta 100 Reciprocity Departure Chart (approximated)

    Quote Originally Posted by CreativeMJP View Post
    Rich815,

    I hear that Fuji Acros is wonderful film. But, how does that song go . . . "If I were a rich man . . ."

    ;-)

    Mike
    Ah yes. For 35mm and 120 not so bad, but 4x5 quite a price difference, you're right.
    -----------------------

    "Well, my photos are actually much better than they look..."

    Richard S.
    Albany, CA (San Francisco bay area)

    My Flickr River of photographs
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    My Photography Website
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  7. #7

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    Thanks for information.

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    Quote Originally Posted by andrew.roos View Post
    Hi Mike

    Welcome to APUG and thanks for posting this.

    However note that the reciprocity failure chart that Ilford provides in the Delta 100 data sheet is not accurate. It is extremely unlikely that these films (which include both conventional and CCG emulsions) have identical reciprocity failure characteristics, so I expect it is sloppiness on Ilford's part copying and pasting the graphs rather than actually performing the measurements.

    My "rule of thumb" based on these measurements is that no correction is required for exposure times up to 4 seconds. For exposures longer than 4 seconds, add an additional 1/3 stop of reciprocity failure correction for each stop of (metered) exposure over 4 seconds.

    Regards
    Andrew
    So you are suggesting, I think: 1.The OP's findings are clearly and substantially wrong
    2. Ilford has been incredibly lazy over reciprocity testing.

    I have no idea how difficult such things are to ascertain but given that Ilford tries to meet customers' requirements to an extent that other manufacturers do not, it seems quite incredible that Ilford hasn't bothered to check on these matters when it is within individuals ability such as Howard Bond to ascertain reciprocity. Why not be as lazy with development times and simply cut and paste ID11 times for say HP5+ for all its films and all its developers? I don't think we are suggesting that Ilford has done this

    Might it be that the methodology used was different?

    Maybe Simon Galley will respond. I would if my company were accused of cutting and pasting our of laziness

    pentaxuser

  9. #9
    johnnywalker's Avatar
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    I questioned their reciprocity charts a few years ago (because I couldn't understand why the charts were basically the same for 4 films, and the reply from Ilford was that "they stood by their charts".
    If I had been present at the creation, I would have given some useful hints for the better arrangement of the Universe.
    Alfonso the Wise, 1221-1284

  10. #10
    Ian Grant's Avatar
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    Quote Originally Posted by johnnywalker View Post
    I questioned their reciprocity charts a few years ago (because I couldn't understand why the charts were basically the same for 4 films, and the reply from Ilford was that "they stood by their charts".
    The issue with reciprocity charts is that the reciprocity failure of films differs depending on the lighting conditions the film's being used for.

    It's often forgotten for instance that films have an ISO speed for Daylight and a different speed for Tungsten light and reciprocity failure is also affected by the type of light. So take 3 extremes a lens stopped down to f45 in sunlight perhaps with an ND filter and an exposure time of 10 seconds, a low light evening shot at f4 @ 10 seconds and a poorly lit tungsten light shot of say f11 @10 seconds.

    There's important differences in the spectral components of those 3 conditions and also the contrasts, so any reciprocity ajustment will be different as will any necessary tweaking (B&W) to get the best contrast range. So this is why Ilford use a single generous reciprocity chart.

    Foma's figures for reciprocity are way different to the figures I found from testing under the conditions I shoot their films.

    Rather than relying on manufacturers charts it's far more importnat to do some tests (or barcket) to find the best exposure adjustment for the conditions you'll be shooting in.

    Ian
    Last edited by Ian Grant; 01-19-2013 at 03:15 AM. Click to view previous post history.

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