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  1. #11
    Chris Lange's Avatar
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    Quote Originally Posted by ic-racer View Post
    Actually if the projected image the same size with each lens (even though the enlarger is higher) there would be still 'conservation of energy and matter' so the light intensity is about the same in each case, assuming the F-number on each lens were set the same. The 'effective aperture' is also the same in both cases because if the projected image size is the same then magnification will be the same in each case.

    Another way to look at it: Would you expect to use a different exposure with your camera when going from a 80mm lens at f8 to a 150mm lens at f8 when you moved the camera back to frame the image the same size.
    Please correct me if I'm wrong, but wouldn't the inverse-square law of light determine that if the head is twice as high, the intensity would only be 1/4 as bright? I know that inverse-square gets weird when involved in optical systems, but as far as I know only a Fresnel type lens makes it irrelevant.
    See my work at my website CHRISTOPHER LANGE PHOTOGRAPHY

    or my snaps at my blog MINIMUM DENSITY
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  2. #12
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    Quote Originally Posted by ic-racer View Post
    The negative is probably pretty thin if your printing exposure is that short with a diffusion head and MG filter in place. Next step is f16 at 5 sec. After that you can sandwich a piece of neutral density material with your contrast filter (if above the negative). Can you show a picture of the negative? You probably don't have any way to measure the density of the shadows or highlights, right?
    Hi ic-racer here is a photo of the negative held up to my computer monitor. I'm not exactly sure how to calculate density...
    Attached Thumbnails Attached Thumbnails negative.jpg  

  3. #13
    Chris Lange's Avatar
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    It looks like the shadows are a little thin, but otherwise it shouldn't be a difficult neg to work with. Less total exposure over a longer time period will give you time to do a little dodging on the shadow detail as well...
    See my work at my website CHRISTOPHER LANGE PHOTOGRAPHY

    or my snaps at my blog MINIMUM DENSITY
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  4. #14
    MattKing's Avatar
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    Quote Originally Posted by Chris Lange View Post
    Please correct me if I'm wrong, but wouldn't the inverse-square law of light determine that if the head is twice as high, the intensity would only be 1/4 as bright? I know that inverse-square gets weird when involved in optical systems, but as far as I know only a Fresnel type lens makes it irrelevant.
    That applies to unfocused light from a point source.

    However, if you use an optical system to focus the light, the intensity of the light at the plane of the easel will depend on the magnification, which is a function of both focal length of the lens and the distance between the negative and the paper.

    If the light from the negative is spread out over the paper, it matters not whether the cone of light is tall and narrow (long lens) or short and squat (short lens).
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  5. #15
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    Quote Originally Posted by teekoh View Post
    Hi, I've attached two images from the same negative showing one printed from a professional lab and the other by me. I'm struggling with short exposure times and flat dark images. I'm using a Durst M605 diffuser enlarger with a GE EKG 80W 19V bulb. My print was enlarged at f11 for 5 seconds while using a Ilford Multigrade #4 filter. I'm guessing 3 or 4 seconds would have been a better exposure time but I thought that was quite short especially with a filter already in place. Do extremely short exposure times impact contrast?

    Thanks for any tips you might be able to share.
    Is the one printed by the lab produced through a wet black & white process? Also and perhaps a silly question, but are you printing onto multigrade paper?
    Last edited by cliveh; 12-01-2013 at 04:05 PM. Click to view previous post history.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

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  6. #16

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    Is your paper fogged??

  7. #17
    Chris Lange's Avatar
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    Quote Originally Posted by MattKing View Post
    That applies to unfocused light from a point source.

    However, if you use an optical system to focus the light, the intensity of the light at the plane of the easel will depend on the magnification, which is a function of both focal length of the lens and the distance between the negative and the paper.

    If the light from the negative is spread out over the paper, it matters not whether the cone of light is tall and narrow (long lens) or short and squat (short lens).
    Thanks for the explanation. I always knew that while shooting (obviously not adjusting exposure for subject distance) but I guess it takes some brain twisting to reverse it in the darkroom!
    See my work at my website CHRISTOPHER LANGE PHOTOGRAPHY

    or my snaps at my blog MINIMUM DENSITY
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  8. #18

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    Are you pulling the prints before they are completely developed? People tend to do this when they find that the prints are becoming too dark. This results in muddy looking prints. Most paper developers recommend a development time of 1.5r to 3 min. Try a shorter exposure time and 30 to 60 sec more in the developer.
    Last edited by Gerald C Koch; 12-01-2013 at 07:45 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  9. #19

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    Quote Originally Posted by Gerald C Koch View Post
    muddy looking prints. Most paper developers recommend a development time of 1.5r to 3 min. Try a shorter exposure time and 30 to 60 sec more in the developer.
    Anything to bring up the contrast!

    To match that you would follow Gerald's advice and print on a contrasty paper, maybe a grade 4, with less exposure and more development. Concentrate on getting the face right, it's the part with the best mid-tone and the focus of the picture.

    I did a quick and cheesy copy+paste of that negative into Paint.NET and did the following to test that theory:

    spread out the levels to full range because the negative isn't dense enough (it needs more development from the low initial exposure?)
    goosed the contrast up 30% and lowered the brightness -15% (this brought out the face really well)

  10. #20

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    If a lab made decent print, it is your process that has an error. Old depleted developer or fogged paper.

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