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  1. #1

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    Changing Time vs Aperture When Making Enlargements?

    In making B&W enlargements going from, say, 8x10 to 11x14, 16x20, or 20x24, is it best to keep the aperture constant and change the time or keep the time constant and change the aperture? Or does it matter?

    Thomas
    Thomas

    No art passes our conscience in the way that film does, and goes directly to our feelings, deep down into the dark rooms of our souls.
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  2. #2

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    Most enlarging lenses give best image quality closed 2 stops. For this reason most of us prefer to fix the aperture and alter the time to suit for different print sizes. It’s the same for color or B&W.

    This and similar ideas were discussed here.

    http://www.apug.org/forums/forum41/8...questions.html
    Last edited by Ian C; 04-01-2012 at 10:53 AM. Click to view previous post history.

  3. #3
    Dan Henderson's Avatar
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    I agree with Ian. Use the aperture that the lens is designed to render sharpest whenever you can. Then if the exposure times get too long or too short, go up or down a stop. One stop either side of the ideal aperture will not make a hugely noticable difference as long as you don't get too close to wide open or all the way down.


    web site: Dan Henderson, Photographer.com

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    I am not anti-digital. I am pro-film.

  4. #4
    wildbill's Avatar
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    i very often use neutral density gel filters over the light source on my colorhead because it's just too bright even on low output and f16 on the lens. you can get these in large sheets (nd 1.5, 3, 6 for about $6 from lee or rosco.
    www.vinnywalsh.com

    I know what I want but I just don't know how to go about gettin' it.-Hendrix

  5. #5
    Photo Engineer's Avatar
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    This is all very true if your paper has low or no reciprocity failure.

    If there is reciprocity failure than speed and/or contrast may change if you change the time.

    In my professional work, I was taught to change the aperture while keeping the exposure time constant! Of course, you pick the center point with time so that lens sharpness is optimal but you have a stop or so on each side of "perfection" to work with between 8x10 and 16x20.

    PE

  6. #6

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    Change one, or both as it suits you.

    You may wish to stop a lens down three stops for a small test print to keep the time sufficient to allow dodging and burning. When you make a bigger print, you may in fact open it up a stop and make a further change to exposure time to make your next print. I often want exposure times to be 'long enough' but not too long.

  7. #7
    vpwphoto's Avatar
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    Its not linear anyway... you'd run out of apertures going from 8x10 to 16x20.

  8. #8
    Bill Burk's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    This is all very true if your paper has low or no reciprocity failure.

    If there is reciprocity failure than speed and/or contrast may change if you change the time.

    In my professional work, I was taught to change the aperture while keeping the exposure time constant! Of course, you pick the center point with time so that lens sharpness is optimal but you have a stop or so on each side of "perfection" to work with between 8x10 and 16x20.

    PE
    Thanks for the reminder. I learned this from datasheets for reversal color print papers, I think the aim was 10 seconds... Bought a 2.8 lens for the purpose... Threw it out because it wasn't sharp enough...

    Really, I don't practice color processes because the chems don't keep 6 months. When it's a hobby, color doesn't give much "time" in the darkroom for the price.

    But I can see how this might pertain to B&W paper if "contrast" or "speed" changes due to reciprocity failure. It makes sense to keep the time consistent as possible. If you have to pick another time for a different print size, then re-evaluate exposure and contrast for that print.

    In practice, I change my aperture from around f/11 to f/22 to keep my 11x14 print times around 32 seconds. But I also keep other relevant variables constant too for example I stick to print size 11x14 and print full-frame. I'll throw in a 2 stop ND filter when making smaller prints.

  9. #9
    Thomas Bertilsson's Avatar
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    Don't be afraid of using your lens away from that 'magical' two stops down optimum.

    If you use a 50mm f/2.8 and usually print at f/5.6 aperture, don't be afraid of f/4, f/8, or even f/11 to get reasonable printing times. Will there be a difference? Probably. In my world, though, it's better to be at a comfortable printing time where the paper stays consistent (avoiding reciprocity failure) than having a wee bit better sharpness. Use what's practical and don't worry about it. That's my advice.

    - Thomas
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  10. #10
    Ian Grant's Avatar
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    For colour work you're better to change the aperture & keep the exposure times constant, reciprocity with colour papers affects the colour balance and contrast.

    In the days before minilabs in professional labs the colour roll-head printers were set up and calibrated and the aperture ring locked so that regardless of the lens used on the turret the exposure remained constant - the degree of enlargement was dependant on which lens was used. This was important because it meant that regardless of the size all machine prints had identical colour correction (and exposure).

    With B&W this is less important but it's still useful to keep times similar as it also helps with dodging and burning at different sizes.

    Ian
    Last edited by Ian Grant; 04-01-2012 at 11:38 AM. Click to view previous post history.

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