Light Meters

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

  1. That is basically correct, and a very good comparison.
    However, the particular gamma correction with JPEG gets
    a bit over 9 stops of dynamic range.

    That compares with u-Law encoding of telecommuncations
    voice frequency circuits, where the SNR of a voice
    channel cannot be greater than 37 dB. Which says that
    if, for example, u-Law were used for the gamma
    correction in JPEG it would result in only about 6 stops
    of dynamic range.
     
    Floyd L. Davidson, Apr 17, 2011
    1. Advertisements

  2. Charles E Hardwidge

    Savageduck Guest

    There you go again. ;-)

    I certainly have enough respect for my self to have not engaged in the
    meat of this debate. In this case I was observing. I was merely
    commenting on the string of posts, four by my count, where your entire
    exchange was with yourself.

    I am also aware of just how proudly and arrogantly you wear your "Pro
    with a preference for film" badge.
    I would just point out that many of us mere amateur hobbyists have a
    long background in the film world and the wet darkroom. It is therefore
    a little presumptuous of you to state that others have not made a
    worthwhile contribution in this Newsgroup. It is after all
    alt.photography, not alt.photography.exclusive.irishpro.

    I must admit I haven't use a hand held light meter since about 1964
    when I got my Spotmatic.
     
    Savageduck, Apr 17, 2011
    1. Advertisements

  3. Charles E Hardwidge

    The Bailey Guest

    Duck, youu know that charges of talking to oneself is a form of abuse
    across usenet that you copied , making yourself out to be a wiseguy.
    If you want to abuse me, at least be original !
     
    The Bailey, Apr 17, 2011
  4. Charles E Hardwidge

    Savageduck Guest

    Why?
    Just how would one go about originally abusing an Irish photographer from Cork?

    Are you trying to say you didn't respond to your own ramblings, ...er,
    posts in this thread?
    I was just saying, what seemed obvious. Carry on, I will leave you to
    your pontificating.
     
    Savageduck, Apr 17, 2011
  5. Charles E Hardwidge

    Pete Guest

    Over the last few months my ability to concentrate, read and
    understand, and transfer technical things into useful spreadsheets etc.
    has been improving, which is great. My ability to write and speak has
    been getting much worse. Writing has always been very difficult so I'm
    used to it, but it's now taking absurdly long to write each sentence.
    Speaking was just plain hard work, but now I'm suffering from "buffer
    underrun" and data corruption! (At least I can still laugh about it.)
    Losing the ability to communicate is utterly demoralizing and the
    long-term implications are scary.
    That's a great image. Night shots have always been my passion so I'm
    learning how to capture them in two different styles: "natural" and my
    own surreal style.
    Thanks for your reply, Noons.
     
    Pete, Apr 17, 2011
  6. Charles E Hardwidge

    Alan Browne Guest

    JPG is non-linear. The DR is the same as the original but there is loss
    of fine gradient information. Such loss is not discernible on a display
    or a print - but of course results in more loss during edit. Which is
    why it is preferable to do extensive image processing with a TIF or raw.
     
    Alan Browne, Apr 17, 2011
  7. The dynamic range is not necessarily the same as the
    original, because it is a simple fact that the dynamic
    range of JPEG is limited by the bit depth. Because the
    data is gamma corrected it is not the same limit that
    linear encoding would have, but it is limited none the
    less.

    If the original had less dynamic range than the limit for
    JPEG, there is no change. If the original had greater
    range, some of it will be lost.
    The loss of "fine gradient information" is of course a
    loss of dynamic range, by definition.
     
    Floyd L. Davidson, Apr 17, 2011
  8. Charles E Hardwidge

    ASCII Guest

    If I wanted to edit or dither a JPEG, would there be
    enough advantage to convert to TIF and back
    to offset any losses that occur during conversion?
     
    ASCII, Apr 17, 2011
  9. Charles E Hardwidge

    Alan Browne Guest

    No. What was lost was lost irretrievably.
     
    Alan Browne, Apr 17, 2011
  10. Charles E Hardwidge

    Noons Guest

    Dang! Know more or less what you mean, I went through a memory loss
    episode 12 or so years ago and things looked bad then. Much better
    now but I can definitely relate to the demoralizing feeling.
    Hope it gets better. As we say here in Australia: chin-up, matey!
    Thanks. Nothing wrong with that in my book! Interpretation of an
    image is entirely a personal thing. You have worked out a style you
    like and sorted out the gear to get you there. That is essentially
    what photography is all about, IMHO.

    I stick with film for the time being not because of any particular
    desire to use it but because it gives me the "natural" results I
    prefer. I'm close to getting a workflow in digital that gets me the
    same. The Oly EPL1 is nearly there. Unlike film, the camera itself is
    incredibly important, with digital. I'm hoping that a try of the D700
    I'm planning and (maybe) a twirl through the foveon space will get me
    there. If so, then I'll gladly ditch film - except for MF. If not,
    then I'll keep using it.
     
    Noons, Apr 18, 2011
  11. Charles E Hardwidge

    David Kerber Guest

    14 bits in the camera, but .jpgs only have 8. You lose a lot right
    there.
     
    David Kerber, Apr 18, 2011
  12. Charles E Hardwidge

    David Kerber Guest

    Yeah, brain fart on my part; sorry.
     
    David Kerber, Apr 18, 2011
  13. Dynamic range isn't dependent on bits. 0 and 1 are white and black before we
    get into anything else. Tonal quality and detail resolution are where lower
    bits can be a PITA. My camera does 12 bit raw (which is a bit crap) but 14
    bits definitely has more to play with especially in the darks.

    So there's a few things to separate here. Dynamic range, tone gradation, and
    detail are all different things that come together in a mix. More bits can
    definitely help especially during processing but, ultimately, you're bound
    by the limits of the output whether its screen or paper.

    Most slide has a low dynamic range but can look fantastic. Some of that is
    down to shooting by using good lenses, exposing correctly, and composing
    scenes with good saturation. Is digital there yet? Perceptually, yes. And
    for a lot of end uses that's good enough. Perfect? Nope.

    For good detail and tone across the range digital has some way to go. 14
    bits doesn't even begin to be enough although 32 would be getting there.
    Noise is still an issue. So just at the time people have assumed digital is
    a 'solved problem' things could change again and quite dramatically.
     
    Charles E Hardwidge, Apr 18, 2011
  14. Charles E Hardwidge

    Pete Guest

    Confusion of terms. You mentioned previously "That compares with u-Law
    encoding ... where the SNR of a voice channel cannot be greater than 37
    dB." That is the maximum signal to distortion ratio (SDR) of the
    system. The maximum signal to noise floor ratio (SNR) is over 70 dB,
    which is the dynamic range of the u-Law encoding system.

    SDR is the result of limited system resolution ("fine gradient
    information"). SNR is the result of limited system dynamic range due to
    noise and spurious signals.

    The values of SNR and dynamic-range may not be the same. Noise is
    usually perceptually weighted to better indicate perceived system
    performance thereby enabling comparison of different systems. For
    telephony channels is is common to use psophometrically weighted noise
    values in the determination of SNR.

    It's difficult (perhaps inappropriate) to apply this terminology to
    JPEG and other reduced bit-depth image encoding systems because the
    "signal" will likely not have been dithered correctly before it is
    encoded. Two examples of when this may occur: a JPEG was edited; noise
    reduction was applied. Furthermore, perceptual noise weighting cannot
    be applied without knowing the viewing angle of the image.



    When decoding an 8-bit image value, level 0 means black i.e. the
    brightness = 0, therefore the dynamic range of the system appears to be
    infinite. Obviously, the system does not have infinite dynamic range so
    it's convenient to use the decoded value of level 1 as an indication of
    dynamic range. Below, I have abbreviated Adobe RGB 1998 to ARGB:

    Decoded level 1
    ---------------
    sRGB 11.69 f-stop
    ARGB 17.58 f-stop

    Clearly, ARGB has a much greater dynamic range than sRGB. Indeed, it is
    much higher than that of cameras and display devices.

    Now let's have a look at level 2:

    Decoded level 2
    ---------------
    sRGB 10.69 f-stop
    ARGB 15.38 f-stop

    Suppose we want to edit the JPEG and recover deep shadow detail. Were
    stuffed with sRGB because the resolution (difference between level 1
    and level 2) is a whole f-stop. Does ARGB give more resolution?

    level f-stop
    ------------
    6 11.90
    7 11.41
    8 10.98
    9 10.61

    Yes, about two and a half times as much resolution. (The slightly wider
    gamut of ARGB makes very little difference to this improvement.)

    This is why some camera manuals suggest recording in Adobe RGB if
    extensive post processing is to be performed, or recording in sRGB if
    the JPEGs will be printed after minor or no post processing.

    We haven't gained something for nothing: more resolution in the shadows
    must mean less resolution in the brighter areas (because we have only
    256 levels). The difference has been distributed and kept fairly small:

    18% grey
    --------
    sRGB 0.0261 f-stop
    ARGB 0.0270 f-stop

    White (step 254 to 255)
    -----------------------
    sRGB 0.0129 f-stop
    ARGB 0.0125 f-stop

    ARGB has slightly worse mid-tone and slightly better highlight
    resolution than sRGB.

    If anyone is interested to see a comparison of these two encoding
    standards mapped onto the Zone System, I'll have a go at doing it.
     
    Pete, Apr 18, 2011
  15. Charles E Hardwidge

    The Bailey Guest

    Yes, I notice that all three local professionals for our local
    newspapers are having these problems , even allowing for newspaper
    print screening. Two of them would probably not be considered pro's
    but one is.
    And this is despite their using Canon 5D mark 11 , and canon 7D with
    Canon L lenses.
    Their pics are not a patch on the former work by one of them in the
    film print era ten years ago.
    I am seeing this elsewhere with newspaper photos too.
    To be frank , their Digital quality is crap!
     
    The Bailey, Apr 18, 2011
  16. Charles E Hardwidge

    Pete Guest

    Sorry Charles, ultimately it is photon shot noise that sets the noise
    floor. ISO speed rating is (usefully) defined as 0.8/lux-seconds
    exposure for Zone I, so that is as far as technology can possibly get.

    More bits will only help those wishing to capture and resolve a black
    cat in a coal cellar having a window onto a white bird on snow. This is
    impossible with small silicon-based sensors: the distance it takes a
    photon, travelling through silicon, to have a 63% probability of
    generating an electron has been established therefore the only way to
    increase dynamic range and resolution is to use something other than
    silicon.

    Until then, more than 16-bits ain't gonna be much help to small format
    cameras. For a 2 megapixel large-format camera, yes, many more bits
    would be very useful.
     
    Pete, Apr 18, 2011
  17. Vision doesn't need to be supported by facts. :p

    A few years back I sketched out a game design concept to a, then, aspirant
    game artist. He said it was impossible. Five years later almost the entire
    industry was based on similar ideas and technology. In the same way film has
    been overtaken by digital the fixed pipeline has been overtaken by shaders.

    Now, I think, there's problems with sensor design and the underlying tech
    but having the balls to ask the /right/ questions can discover /different/
    answers. Sub wavelength lenses? Reality.

    I was thinking today about my life going in a loop and just read about a
    similar thing in a photog magazine (these coincidences stick to me like iron
    filings to a magnet). Dammit. I want my Kodachrome.

    Whatever happens there's potential for chance with sensors, lenses, and
    standards so /something/ is going to change. The only question is what, why,
    and when. Maybe when we've been milked dry or some bright spark gets in a
    hurry. Dunno but it /will/ happen.
     
    Charles E Hardwidge, Apr 18, 2011
  18. My local paper is just crap. Period. Hick right wing mentality keeping a
    foot on the throat of excellence as much as any union baron. Digital didn't
    bring any change in the level of shit just rearranged it.

    The local hipster magazine has better photo or, rather, more "arty" and less
    obviously crap photos but the exposure is blown or flat. There's nothing in
    the composition that's classic in any sense.

    I don't want to get too judgemental about this but the attention they're
    paying to exposure and print isn't great. How much that's down to politics
    or paying chickenfeed I don't know. Better is certainly possible.
     
    Charles E Hardwidge, Apr 18, 2011
  19. Charles E Hardwidge

    Pete Guest

    Thanks for that, Noons. I'm very pleased to hear that you pulled through it.

    Chin-up is right: I've always been determined to be a survivor rather
    than a victim of circumstance. Heck, if I totally lose my ability to
    communicate in writing and verbally it wouldn't be so bad - I could
    communicate through my style of surreal art. Does it matter if people
    like it or hate it? Not really. As long as it provokes a reaction I
    guess it's worth pursuing.

    In an attempt to win the battle with my failing communication I decided
    to face it head-on after your words of encouragement. Today, I spent
    seven hours writing my post to Floyd, had a long break, then two hours
    writing my short reply to Charles.

    The last thing I want to become on any newsgroup is a pest/troll.
    Perhaps, it is my profound difficulty to comprehend the difference
    between making useful input and being a nuisance that is making my
    "output" communication go down the tubes.
    My opinion too.
    I hate editing. My intuition is based on a few different film types so
    what I should be using is a film camera plus image stabilised lenses,
    but hey, I'm determined to master my D700 and NX2. There's one thing
    for sure - that combination is streets ahead of my ability as a
    photographer so I won't ever outgrow it :)
     
    Pete, Apr 18, 2011
  20. Charles E Hardwidge

    Pete Guest

    Or maybe, we've succumbed to the false promises of advertising hype...
     
    Pete, Apr 18, 2011
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.