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  1. #31

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    This is an interesting and informative thread, and I'm glad Bill started it.

    The first - only - book on enlarging I've read is Nocon's "Photographic Printing", and having read it, I promptly forgot everything he had to say about using f/stops for test strips. Accordingly I've been doing 4-8-12-16-20 sequences; now as DannL implied above, if it gets you to the right exposure, it doesn't matter much how you got there.

    Nevertheless I've got my Nocon out again and will have a go. It does seem slightly mad that while I understand perfectly the reciprocal relationship between exposure and f/stop when I'm taking photographs, I haven't been able to carry it into the darkroom ...

    At the risk of appearing extremely dim, though, one thing I really don't get is this:

    Quote Originally Posted by Bill Burk
    I start the timer with the strip uncovered - the whole strip gets a random amount of starting time. Then I cover all but a 1/2 inch x 11 inch and start counting clicks
    If you look at your strip and say "Ah! 8 seconds is just right!", how is the random exposure time accounted for?

  2. #32

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    The random amount of starting time is not random meaning "unknown". I assume what Bill means is "arbitrary" vs "random".

    Anyhow, regarding "f-stop" sequences vs arithmetic, it's just a different method. That's all.

    The most important thing is to make your test strip/print as informative as possible. One fairly common criterion (rightly so in my opinion) is for the test strip/print to go from obviously too light to obviously too dark. Some people find a "stop" sequence more efficient, and like to think of subsequent burning and dodging adjustments in terms of stops relative to the base exposure.

    Another way to make test prints as informative as possible is to use a full sheet and not skimp on paper by cutting it into little strips. Perhaps calling it a test "strip" is the problem. I prefer test print. Then proceed to work prints. For subsequent burning and dodging tests, smaller pieces of paper can be used quite effectively. John Sexton's "puzzle pieces" approach, for example.

  3. #33

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    I will withhold critical judgment on the f-stop thingy until I've had a chance to study this again. I looked into this years ago and ran the other way. But now that I'm older . . . I can't run like that. Meantime I found the following doc, and I'm reading it intensely.

    TimingExposureEd2.pdf

    One problem I might have, and as it typically goes, if the base exposure of 20 seconds is correct for this series of negatives/paper, how to build a strip around that figure in f-stop times. ie; 15, 17.5, 20, 22.5, 25 is an easy sequence to calculate on the fly. An accuracy of plus or minus 1/2 second would be pushing it with my timer. When compared to the chart with "base exposures" in the document above, the differences in exposure times are slight.
    5x4, 4x5, Half-Plate, 5x7, 8x10 and 6x7cm

  4. #34

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    I prefer to use a simple percentage progression.

    This works in exactly the same way as f-stop timing (i.e., you get the same amount of density change between each strip) but does away with the logs, the decimals and thirds of anything.

    A 30% test strip might go like this (in seconds): 10, 13, 17 (rounded from 16.9), 22 (rounded from 22.1), 29 (rounded from 28.6), 37, 48.

    Since I use a metronome to print, It is simply a matter of counting: 10 - 3 - 4 - 5 - 7 - 9 - 11 - off.
    The values are rounded, but very close to 30%.

    I determine my basic exposure from a highlight value and then start to make test prints. If I need to change contrast much (i.e., change graded paper grades or more than a few cc for VC paper on the dichro head) then I'll make a new test strip.

    Contrary to how others work, I find a test strip to be invaluable and economical.

    Best,

    Doremus

  5. #35

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    A benefit as I understand it from the fstop method is that if say 4 secs in right for the basic exposure but 2 more strips at say 1/3rd stop more each is right for the sky then if you switch to bigger or smaller paper then once you calculate the correct basic exposure from the change in projection size then the sky will still be 2/3rds of a stop more so no need to re-calculate all the different exposures on the print

    It clearly helps if you have an fstop timer but Ralph Lambrecht's fstop table gives you the times in secs

    pentaxuser

  6. #36
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    Quote Originally Posted by Bill Burk View Post
    I start the timer with the strip uncovered - the whole strip gets a random amount of starting time. Then I cover all but a 1/2 inch x 11 inch and start counting clicks. These are the ticks I count which are third-stops down from 40 seconds... (8 - 7 - 5 - 4 - 3). After each interval, I move the cardboard about a half inch until the whole strip is uncovered and receives the remaining time on the timer.
    All the paper is uncovered for 40 seconds, the next longest time is 40 - 8 = 32 seconds, the next strip is 40 - 15 = 25 seconds and so on. It shouldn't matter which seconds I choose to take away (beginning, middle or end), but I give a few seconds for lamp warm-up time in my system.
    Last edited by Bill Burk; 11-13-2013 at 02:32 PM. Click to view previous post history.

  7. #37

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    Quote Originally Posted by pentaxuser View Post
    A benefit as I understand it from the fstop method is that if say 4 secs in right for the basic exposure but 2 more strips at say 1/3rd stop more each is right for the sky then if you switch to bigger or smaller paper then once you calculate the correct basic exposure from the change in projection size then the sky will still be 2/3rds of a stop more so no need to re-calculate all the different exposures on the print

    It clearly helps if you have an fstop timer but Ralph Lambrecht's fstop table gives you the times in secs

    pentaxuser
    This relationship works with percentage timing also. Plus all dodging and burning can be recorded as percentages of the basic exposure time as well, which seems to me to be rather more complicated with f-stop timing (I can't figure out how to wave a dodging wand around for 2/3-stop..., I like to just count seconds with my metronome).

    When I scale a print up or down, I find the basic exposure using a test strip (as described above) and then make a pilot print with the manipulations I've recorded adjusted for the new print size as percentages of the basic exposure time. This is a good starting point for printing at a new size.

    Best,

    Doremus

  8. #38
    Bill Burk's Avatar
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    Doremus,

    I think percentage timing is mathematically the same as f/stop timing... Look at your counts and mine... They're identical! I call mine 1/3 stop and you call yours 30%

  9. #39

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    I received the Lootens book and scanned through it. It was definitely worth the investment. I found it interesting how this book complements the "The Craft of Photography" by David Vestal, another book I had recently acquired.
    5x4, 4x5, Half-Plate, 5x7, 8x10 and 6x7cm

  10. #40
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    Would it not be the same at lets say 10 seconds... but if you go up in printing time I think 1/3 stop will change the density more than a 30% change.

    base your time at 100 seconds , changing 1/3 stop will look the same as lets say 70 seconds??? You are now into reciprocity failure.Yes?No

    Quote Originally Posted by Bill Burk View Post
    Doremus,

    I think percentage timing is mathematically the same as f/stop timing... Look at your counts and mine... They're identical! I call mine 1/3 stop and you call yours 30%

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