Light Meters

Discussion in 'Photography' started by Charles E Hardwidge, Apr 11, 2011.

  1. My opinions are never knowingly undersold but I'm sure there's some truth in
    what you're saying.

    Being a Zen-Taoist-Stoic (with a dash of Shinto) life can seem a bit crazy
    and truth a little elastic at times. Having spent half of my life trying to
    learn things I'm now trying to forget them as I found myself knowing more
    and more about less and less.

    This has been an interesting discussion. Not sure I've learned much but the
    simple basics have been worth a visit.

    I haven't looked at a printed magazine for years. Didn't have time tonight
    but might flip through some of the glossies and other mags in the local shop
    sometime just to get a grip on what's being published.
     
    Charles E Hardwidge, Apr 18, 2011
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  2. Charles E Hardwidge

    Paul Furman Guest

    Just shoot raw and don't overexpose the whites (but come close). Post
    processing might get more complicated.
     
    Paul Furman, Apr 19, 2011
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  3. Charles E Hardwidge

    The Bailey Guest

    My point is that film does it without really trying, gloriously. Wish
    someone who is not a digital addict would respond.
     
    The Bailey, Apr 19, 2011
  4. Charles E Hardwidge

    Alan Browne Guest

    In absolute terms you're right. However, as pointed out to you many
    times, this has not overcome the convenience and lower operating costs
    of digital for the vast majority of photographers, including
    professional wedding and product photographers.

    Nor does it negate the high DR of cameras such as the FujiFinePix S3 - a
    hit with wedding photogs, but now on the shelf due to the leading DR of
    cameras such that you mention which do a fine enough job with the
    classic black tux and white wedding dress scenario.

    IOW: Declare victory and move on.
     
    Alan Browne, Apr 19, 2011
  5. OK so far. What hinders me to place 255 at (near) infinite brightness
    (outside the fact that it's physically rather ... ah, hard, to create
    and to view)?
    I'm lost ... on what basis do you calculate that (as an absolute
    value)?

    -Wolfgang
     
    Wolfgang Weisselberg, Apr 19, 2011
  6. Charles E Hardwidge

    Pete Guest

    Hi Wolfgang.

    I calculated the linear values of the sRGB reverse transformation using
    the link below with alpha=0.055 and gamma=2.4:

    Csrgb = (channel level)/255 in order to normalize the level range from 0-1
    Clinear = (Csrgb+0.055)/1.055)^2.4 when Csrgb > 0.04045
    Clinear = Csrgb/12.92 when Csrgb <= 0.04045
    f-stop = -log2 Clinear

    It seems to agree with many other references, but here are some
    landmark points you can check:

    level Clinear
    -------------
    128 21.6%
    118 18.1%
    099 12.5% (a common metering point for Zone V)
    022 0.802% (nearest Zone I ISO definition point)
    001 0.0304% => contrast ratio=3295:1 => 11.69 f-stops

    However, a Kodak document I read ages ago suggested that the 18% grey
    card *should* coincide with level 114 not 118. This is very sensible
    advice because it means level 255 represents 107% white, which allows a
    little room for specular hilights and sharpening overshoot.

    Obviously, a different (and hopefully correct) method was used for ARGB values.

    If any of this is incorrect then please let me know.

    <http://en.wikipedia.org/wiki/SRGB>
     
    Pete, Apr 19, 2011
  7. Floyd and Clark are right ... you just have to be careful how you expose the
    digital. You have to be paranoid about using your camera's
    histogram correctly. Hint: it almost certainly is for the JPEG
    result, not raw. If you save raw, which you should, set the in-camera
    JEG to a very low contrast setting. The experiment to see exactly what
    the histogram says about blown highlights.

    Use of the camera's automatic exposure is designed to to make the JPEG
    "look OK" with a standardized "development" and that often makes a very
    bad decision as to where to put highlights.

    Doug McDonald
     
    Doug McDonald, Apr 19, 2011

  8. To do the Zone system idea in digital, do this:

    1) use RAW

    2) learn to expose for the highlights as in my previous post ...
    this requires experimentation with you digital camera

    3) "develop" using Photoshop

    4) learn to use Photoshop's tools well, especially the highlight/shadow
    feature (set the radius to 200-400). Also learn "quick mask" to
    adjust contrast in limited areas of the picture.

    Doug McDonald
     
    Doug McDonald, Apr 19, 2011
  9. Charles E Hardwidge

    Paul Furman Guest

    :-(
     
    Paul Furman, Apr 22, 2011
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