RAW Files With Powershot G3 - Contrast and ISO

Discussion in 'Digital Photography' started by Dr. Slick, Oct 21, 2003.

  1. Dr. Slick

    Dr. Slick Guest

    Hi,

    I've noticed with my G3, that i can take photos almost 2 full
    f-stops away, 0.4" to 1/8 seconds @ the widest aperture of 8, and i
    can get the same final image in Photoshop, by just adjusting the
    brightness. The contrast needs to be adjusted the same for any of the
    exposures in RAW format, it seems.

    So it seems that to a certain degree, the exposure you get is not
    as critical in RAW format, as long as you will manipulate them in PS
    yourself. Although i'm sure you will lose some dynamic range if you
    get too over- or under-exposed. But the final images for these two
    settings were virtually indistinguishable from one another (ISO of 50
    using Tungsten).


    Another question sparked by the other post is: How does the ISO
    of digital compare with analog ISO of film? It makes complete sense
    that the faster sampling from the CCD with the higher ISO would give
    you more noise, and the slower settings have over-sampling, so the
    noise should be less.
    But it's really fascinating that this has carried over into the
    digital camera world too: that a faster image will give you more
    noise or more grain.

    It's like you never get something for nothing, if you want fast
    food, that's what you'll get! Digital OR Film.

    Ok, and i assume they tried to make the digital ISO readings the
    same as the analog film ISO, but when i used an %18 grey card with the
    spot metering on my G3, the pics turned out a bit over-exposed, or on
    the bright side.

    Can you use a Luna-Pro light meter with your digital camera?


    Slick
     
    Dr. Slick, Oct 21, 2003
    #1
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  2. Dr. Slick

    Dr. Slick Guest

    (Dr. Slick) wrote in message news:<>...
    > Hi,
    >
    > I've noticed with my G3, that i can take photos almost 2 full
    > f-stops away, 0.4" to 1/8 seconds @ the widest aperture of 8, and i
    > can get the same final image in Photoshop, by just adjusting the
    > brightness. The contrast needs to be adjusted the same for any of the
    > exposures in RAW format, it seems.
    >
    > So it seems that to a certain degree, the exposure you get is not
    > as critical in RAW format, as long as you will manipulate them in PS
    > yourself. Although i'm sure you will lose some dynamic range if you
    > get too over- or under-exposed. But the final images for these two
    > settings were virtually indistinguishable from one another (ISO of 50
    > using Tungsten).
    >
    >
    > Another question sparked by the other post is: How does the ISO
    > of digital compare with analog ISO of film? It makes complete sense
    > that the faster sampling from the CCD with the higher ISO would give
    > you more noise, and the slower settings have over-sampling, so the
    > noise should be less.
    > But it's really fascinating that this has carried over into the
    > digital camera world too: that a faster image will give you more
    > noise or more grain.
    >
    > It's like you never get something for nothing, if you want fast
    > food, that's what you'll get! Digital OR Film.
    >
    > Ok, and i assume they tried to make the digital ISO readings the
    > same as the analog film ISO, but when i used an %18 grey card with the
    > spot metering on my G3, the pics turned out a bit over-exposed, or on
    > the bright side.
    >
    > Can you use a Luna-Pro light meter with your digital camera?
    >
    >
    > Slick


    Anyone care to answer?

    Slick
     
    Dr. Slick, Oct 22, 2003
    #2
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  3. Dr. Slick

    MikeWhy Guest

    "Dr. Slick" <> wrote in message
    news:...
    > Hi,
    >
    > I've noticed with my G3, that i can take photos almost 2 full
    > f-stops away, 0.4" to 1/8 seconds @ the widest aperture of 8, and i
    > can get the same final image in Photoshop, by just adjusting the
    > brightness. The contrast needs to be adjusted the same for any of the
    > exposures in RAW format, it seems.
    >
    > So it seems that to a certain degree, the exposure you get is not
    > as critical in RAW format, as long as you will manipulate them in PS
    > yourself. Although i'm sure you will lose some dynamic range if you
    > get too over- or under-exposed. But the final images for these two
    > settings were virtually indistinguishable from one another (ISO of 50
    > using Tungsten).


    It depends on the tonal range of the captured image. More often that I would
    have expected, the histogram is a narrow hump on a broad plateau. There are
    few salvagable shadow details, and no real highlights to speak of. This
    sounds like what you describe. Since RAW doesn't make any in-camera
    adjustments for you, what you shoot is what you get. Shooting JPGs, it would
    have expanded the usable tones similar to the first operation you would
    apply in Ps.

    One could argue this both ways. It seems apparent that there isn't enough
    tonal detail to warrant the additional work in processing RAW. You might as
    well hope for the best and accept the iffy, but usually not altogether bad,
    result the onboard logic gives you. OTOH, it's precisely these difficult
    shots that benefit most from the hand tuning that only a skilled and
    knowledgable person can bring. RAW gives you the cleanest possible start.
    The onboard logic is pretty good, but it can't give great results in all
    possible situations.

    I shoot RAW because I expect to spend time in Ps on each frame I keep. At
    the very least, almost all JPGs benefitted from a few tweaks to the curves.
    Lighting and conditions outside the studio being what they are, the vast
    majority require much more detailed adjustments. Conversion time is small
    compared to the time spent on corrections and targetting for print. 16-bit
    TIFFs give as much detail as possible to start from. (I've recently taken to
    converting without even rough WB and exposure corrections, preferring to do
    it with the better tools in Photoshop. Why correct twice, with the attendant
    losses?)

    That being said, RAW is definitely not user friendly. I wouldn't consider it
    without GB cards, a firewire reader, and a fast PC with plenty of harddrive
    space. Reviewing CRWs is much slower than just browsing a folder of JPGs,
    sometimes painfully so depending on the app. Even cheapie point-and-shoots
    deliver JPGs that are surprisingly usable (if you're not too picky).

    > Ok, and i assume they tried to make the digital ISO readings the
    > same as the analog film ISO, but when i used an %18 grey card with the
    > spot metering on my G3, the pics turned out a bit over-exposed, or on
    > the bright side.
    >
    > Can you use a Luna-Pro light meter with your digital camera?


    dpreview publishes ISO to EV and noise curves, as well as qualitative and
    quantitative comparisons with other cameras.

    I've only ever used the through-lens meter. I would be ever so pleased to
    not have to carry a gear bag again. Shooting a handy neutral gray object
    tells you more about the light than you can hope to grab with a meter. It
    would be nice to have a real reference card, but I find the trade off
    livable. Not that I'm not in the market for a durable, credit card sized
    card. I suppose somebody somewhere makes one... I'll find it when it becomes
    important enough. Every now and again, I think about printing off a few 2x3
    cards on semi-gloss, but never seem to get around to it.
     
    MikeWhy, Oct 23, 2003
    #3
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