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  1. #21

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    Quote Originally Posted by Photo Engineer View Post
    Kodak used to recommend a single 60 second exposure with a cardboard covering the print for varying times. Thus the portion of the strip exposed for the full 60 seconds would be darkest and each of the sections would recieve 10 seconds less exposure.

    There are three reasons why you should not use multiple exposures.

    1. Light bulb on and off cycle is unpredictable. (timer error especially at short times)

    2. Light bulb on and off afterglow is uneven and startup changes as the cycles continue. The bulb filament is warmer each cycle and starts differently. Hue changes as well with heat.

    3. Less commonly known, some photo products don't respond evenly to multiple exposures. There is a kind of a reciprocity failure effect that is cumulative. This BTW, was a serious problem with earlier laser color papers as the overlapping scan lines got multiple exposures and the paper response was not the same as with regular white light exposure. That has now been corrected.

    PE
    i would suggest there are problems of control and accuracy with any procedure, for istance in the above 60sec scenario, can the printer accurately cover the paper each 10 secs, what if one segment was actually 10.5 and the next was 9.5

    as for f stop printing, it sounds logical, but at some stage you have to decide on fractions of a stop, half a stop more than 20 is 28.3, not 30, but what if you did 30, who'd notice, 1.7 secs in 20 is not gonna make any appreciable density difference

  2. #22

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    I use a Kodak step wedge to get close and use an Ilford em-10 for the rest of the roll, Well worth the 20 dollars I paid for it you can easily change enlargement ratio and the adjust the f-stop to match the same metered area. I own a Color Star 2000 for color but for black and white the em-10 is all you need.

  3. #23
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    I became familiar with f-stop printing yesterday, via this thread. I'm doing the forehead-slap now too. Duh. I will be using this table:

    (One full stop separates each column.)

    5.0 seconds 10.0 seconds 20.0 seconds 40.0 seconds 80.0 seconds
    5.9 seconds 11.9 seconds 23.8 seconds 47.6 seconds 95.2 seconds
    7.1 seconds 14.1 seconds 28.2 seconds 56.4 seconds 112.8 seconds
    8.4 seconds 16.8 seconds 33.6 seconds 67.2 seconds 134.4 seconds


    And when I'm satisfied, I may invest in an f-stop timer.

  4. #24

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    trouble with a table like that one is the steps are too great... bit like the Kodak exposure pie (although you can expose this for 30 secs and get closer segments). Ok for someone who has absolutely no idea of what exposure they'll need.

    I'm a seat of the pants, two step printer. I wouldn't recommend this to anyone! I look at the neg and proof sheet to guestimate a starting point then do a test strip concentrating on highlights at the starting point and 1 or 2 second segments depending on how confident I am of my reading of the neg. Occasionly I'll use a sequence like 3,1.5,1.5,3,3. Sometimes I'll check with the exposure meter (Colorstar 2000) to see I'm in the ballpark (it's pretty accurate but I like to run the test strip anyway). Once I've processed the test strip I pick the segment I like, set the timer and do another test print, usually with a bigger piece of paper. I may or may not alter contrast and get the altered time (when using my colour enlarger) I usually use the exposure meter to get the altered time as it seems to get that spot on. My 4x5 is a VCCE head so I just alter the filter dial. Might do another one of these, then use a full sheet of paper. While that's exposing I might decide to dodge and burn... on the fly. If I'm using RC paper I'll let the print air dry, fiber gets nuked in the microwave (although I'm not a big fan of this as I reckon the gloss level ends up different to air dried FB). I then decide if that is the final print I want or make further changes... something like that

  5. #25
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    Quote Originally Posted by Nige View Post
    trouble with a table like that one is the steps are too great...
    1/4 stop steps are too big for you?

  6. #26

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    ahh, you go down the table... not across! doh! I just read across!

  7. #27
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    Quote Originally Posted by Nige View Post
    ahh, you go down the table... not across! doh! I just read across!
    There seems to be an error in row 2. Are my eyes bad? Someone check me out on this.

    Thanks

    PE

  8. #28
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    So does anyone here have the experience compare and contrast the f-stop timers that are around?

  9. #29

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    Quote Originally Posted by jstraw View Post
    I became familiar with f-stop printing yesterday, via this thread. I'm doing the forehead-slap now too. Duh. I will be using this table:

    (One full stop separates each column.)

    5.0 seconds 10.0 seconds 20.0 seconds 40.0 seconds 80.0 seconds
    5.9 seconds 11.9 seconds 23.8 seconds 47.6 seconds 95.2 seconds
    7.1 seconds 14.1 seconds 28.2 seconds 56.4 seconds 112.8 seconds
    8.4 seconds 16.8 seconds 33.6 seconds 67.2 seconds 134.4 seconds


    And when I'm satisfied, I may invest in an f-stop timer.
    I find it easier to go like this

    cover at 6 secs
    cover at 8 secs
    etc for 11s
    16s
    22s
    32s
    45s
    64s

    Just remember the aperture series in your camera and presto! Half-stops logarithmic test strips.
    'In the interest of freedom, APUG was just a tad TOO free.'

  10. #30
    lee
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    I use the RH Designs Stopclock timer and it is very accurate and compensates for that problem. It is a little pricey but it a very nice product and I would recommend it to any one wanting to up grade to f/stop printing that is pretty hassle free.

    lee\c

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