Question on enlargers

Discussion in 'Photography' started by Steven Green, Nov 28, 2005.

  1. Steven Green

    Steven Green Guest

    In an age when everyone is going to digital I seem to be bucking that trend.

    I was considering what it would take to setup my own darkroom.
    I already intend to develop my own negatives but I have been researching the
    process of making prints. (from both negatives and slides)

    I am a little confused on one concept.
    The enlarger has a lens ( I get that part )
    It seems to be much like a camera lens with a size in mm and f-stops,

    It seems to me you would want to give an accurate render of the negative on
    paper.
    With a camera usage of the f-stop gives you depth of field, but what do you
    use it for on an enlarger?

    Thanks,
    Steve
     
    Steven Green, Nov 28, 2005
    #1
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  2. Steven Green

    Whiskers Guest

    As far as it goes, that's correct. Enlarger lenses are computed for the
    special case of having a flat subject and a flat object, both very close
    to the lens, but some camera lenses have been used for enlarging. The
    focal length of a normal enlarger lens is the same as the conventional
    'standard lens' for the format it's intended for.
    Well, yes ...
    For most purposes, you use the aperture to adjust the exposure time.
    However, any lens has a 'sweet spot' aperture where the aberrations are all
    balanced out to give an optimum image, and it is worth finding that for
    your enlarger lenses.

    Sometimes you may want to stop down the enlarger lens to get a longer
    exposure so as to give you more time for 'dodging and burning'.

    You can use the 'depth of focus' effect of a small aperture to let you
    tilt or twist the easel to introduce deliberate distortion into the print
    - eg to reduce the 'converging verticals' in a picture of a building where
    the camera was tilted to 'get it all in'. (The 'depth of field' effect
    can also be used to accommodate tilting the negative, if the enlarger allows
    for that).
     
    Whiskers, Nov 28, 2005
    #2
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  3. Steven Green

    dadiOH Guest

    Mostly, to control amount of light. Very short exposures may be
    inaccurate/unrepeatable...stopping down enables longer ones.
    Additionally, stopping down increases depth of field (on the paper)...no
    big deal if paper is flat but not all easels keep it so.



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    dadiOH, Nov 28, 2005
    #3
  4. Steven Green

    test Guest

    It does the same as at your camers: More depth of field means that you
    do not need to focus so exactly or you can compensate some film curling.
    Secondly it effects the time of exposure as with your camera.

    AFH
     
    test, Nov 29, 2005
    #4
  5. Steven Green

    Mike G. Guest

    Another element of the 'controlling the amount of light' theme has to do
    with the size of the print you are making. If you print a neg at 4x6,
    you may have the lens stopped down pretty far for say a 10-15 sec
    exposure. If you then drop your table and/or raise your head and expose
    for a 16x20 print, the same amount of light is much more 'spread out',
    so you would have to open the aperture to compensate. If you increased
    the exposure time instead, you could (would?) be getting into the
    reciprocity failure exposure time range.
     
    Mike G., Nov 30, 2005
    #5
  6. Steven Green

    b.ingraham Guest

    AFH said, "It does the same as at your camera: More depth of field
    means that you
    do not need to focus so exactly or you can compensate some film
    curling."

    The darkroom photographer who does not focus carefully, and instead
    relies on small apertures, is going to end up with unfocussed prints.
    The goal is a tack-sharp photo (in "normal" situations, at least), and
    the best way to do that is to use a good grain focusser. As with a
    camera, great depth of field in the darkroom is an illusion. An image
    is either in focus, or it is not. If it is not, smaller apertures will
    provide the appearance of sharp focus on casual examination. Put the
    final negative or print under an 8X loupe and you'll discover a
    sloppily focussed image.

    Bob
     
    b.ingraham, Dec 1, 2005
    #6
  7. I never cared for grain focus things. I have one and used it on
    occasion, but I could get good focus with just my eyeballs (looking
    closely).
     
    Randall Ainsworth, Dec 1, 2005
    #7
  8. Steven Green

    b.ingraham Guest

    Good eyes are...good. In my experience, especially with fine-grain film
    and subjects without fine detail, it was just about impossible to focus
    prints precisely without a grain focusser. The problem with grain
    focussers is that you get what you pay for, and the cheap ones are
    mostly worthless. I forget the brand I used, but even fine grain could
    easily be seen. My biggest problem was moving the lens in small enough
    increments to achieve perfect focus. It was like trying to crack eggs
    with a tractor!

    Bob
     
    b.ingraham, Dec 28, 2005
    #8
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