Blacks/Close to Black Color

Discussion in 'Beyond the Basics' started by Pure, Jul 15, 2009.

  1. Pure

    Pure TPF Noob!

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    I currently edit on a Macbook Pro, and I notice that whenever I edit photos that have colors near black, I get a ton of artifacts.

    Is this because the monitor lacks gamut to display all of the colors? Will these artifacts show up in prints?

    I took this impromptu, so nobody really cares, but still, this issue with darks will definitely come into play again.

    [​IMG]
     
  2. William Petruzzo

    William Petruzzo TPF Noob!

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    The Macbook Pro was designed to do what you're doing. Unless there's a malfunction, that's definitely not the problem.

    It is possible that your monitor's calibration is really bad and your black point is far too bright revealing artifacts that you otherwise shouldn't see.

    As it is though, I'm not sure that I'm seeing the artifacts you're seeing. In the darker areas I can see some evidence of jpeg compression, but that will likely be resolved by not compressing so much. When you send to print an image either give them uncompressed files (like TIFF files), or jpeg files that are at maximum quality. If you send them a high enough resolution file you won't see any artifacts in print.
     
  3. Pure

    Pure TPF Noob!

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    I used the eye-one display 2 to calibrate. I set white point to D65, luminance to no change, gamma to 2.2, and did everything in a dark room, and made sure I'd been using the monitor for an hour or two, to make sure it was warm.


    The thing is, the sky seems to be somewhat purple/blue, and very dark so they are close to black. I sent out a test print to WHCC to check if the artifacts show.

    I'm still lost as hell though.



    LR2 uses ProPhotoRBG, but I typically use SRBG, and I'm still lost, damn. I'm confused as hell.
     
  4. Garbz

    Garbz No longer a newbie, moving up!

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    No gamut generates no artefacts. It only affects the colours and will cause clipping on the display itself. i.e. all colours above AdobeRGB(0,200,0) would look the same shade of green because the monitor is already as green as it can get. (btw pulled numbers out of my rear it's not quite that simple.)

    Here's a few notes. The sky IS blue/purple changing to orange at the bottom right. It is very very close to black but when I view the image against a black background I can see that.

    Another thing check to make sure that Photoshop is actually correctly loading your calibration profile. Click edit -> Colour settings. Under working spaces you'll see your working RGB profile, DON"T CHANGE THIS!, just click the down arrow on the right and look at the entry "Monitor RGB" (Just look, don't use this entry).
    If your colour profile is loaded correctly it should say "Monitor RGB - somecolourprofile.icc" if it is not loaded correctly it'll say "Monitor RGB - sRGB IEC blah.icc"
     
  5. Pure

    Pure TPF Noob!

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    It seems that a lot of the nasty artifacts come where the dark sky meets clouds. And yes, my PS is using my ICC profile.

    I'm a bit confused. LR2 uses ProphotoRBG in the develop panel to edit, since the color gamut is better. Should I be editing in CS4 with ProphotoRBG? I believe WHCC can take PPRBG, but many users dont use it. I'm very confused!
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    LR2 does not. It uses MelissaRGB a modified version of ProPhotoRGB that is entirely linearised just like the data in your RAW file. The theory is the initial conversion to MelissaRGB allows their controls to work to the best extent where things like highlight Recovery depend a lot on the ability to mathematically edit more colours that monitors can display or printers can possibly print, and more importantly it does all this at the maximum bitrate of the RAW file.

    Only when you export does it pick a profile for you. Ultimately the idea is if you want maximum colour range reproduction then you pick a profile that is larger than the colour range of your image. In 99% of cases my images fit nicely into sRGB so even AdobeRGB is overkill. The colour gamut of standard matte paper also is just barely larger than sRGB so unless you're using some awesome printing process and a pro lab, or have a nice wide gamut monitor there's no reason really to battle with the larger gamuts.

    That's not really the issue here though. Colours which fall outside the gamut go through a conversion process. For photography this is called the "Perceptual" rendering intent. The colours are clipped at their maximum, and the most saturated colours around the image are scaled ever so slightly so that the result does not look like clipping. The end result is entirely artefact free, looks natural, and covers the target gamut nicely.


    As a matter of interest are you working with an original RAW file, and how much editing have you done to the image? There are a few factors that could be in play. Posterisation from editing the file too much. Posterisation from editing a file in 8bit rather than in the original or larger bitrate. If the saving is the problem, well most if not all lossy compression algorithms sacrifice the dark and the blue channels since the eye is least sensitive to these. One thing thought, your image does have artefacts, but it's a question of why are you seeing them so much.

    I can see them but only just in the original. At the brightest point in there the red channel has a value of 22. I expect this would be plainly noticeable on any well calibrated screen in a dark environment. Also are you viewing your screen dead on? The problem with laptops is the gamut varies with viewing angle very dramatically. For instance my work laptop (admittedly a bad screen) when I view a solid 128 middle grey head on, the top of the screen would be somewhere around 180 and the bottom around 80, it is that bad. So taken note of what it looks like at different viewing angles and share, I haven't used a mac book pro.

    Your image with the contrast boosted.
    [​IMG]
     
  7. Pure

    Pure TPF Noob!

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    I did this photo for fun, so I don't really care that much, but still.

    This is what I did from the original RAW, and yes I'm using 16bit/channel.

    WB: 4800
    Tint: -6
    Exposure: +.33
    Fill Light: 6
    Blacks: 8
    Brightness: +30
    Contrast: +33
    Clarity: -10
    Vibrance: +8
    Saturation: +6
    Highlights: -6
    Lights: -8
    Darks: -6
    Shadows: 0
    Vignette: -23, mid: +3

    Unsharp mask and Reduce noise in CS4.


    Also, what I see in develop SHOULD be color correct, since the Library tab uses a different color space?
     
  8. GeneralBenson

    GeneralBenson TPF Noob!

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    I have a new MBP, and I have to say, the monitor is insanely awesome. I think the dark colors are where this monitor looks best. Could it be that because the monitors has such good bottom end, that is why you're seeing all the other colors in you darks, that on other monitors would all just fade to black?
     
  9. Pure

    Pure TPF Noob!

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    i have no idea...still...so annoying.
     
  10. Garbz

    Garbz No longer a newbie, moving up!

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    I'm going to point my finger at fill light. It takes the darkest points of the image (the ones with the least amount of information and boosts them). Not something that is good in an image that is mostly black, but something that works well in a light image with a few darkish points. That with the +.33 exposure compensation is likely what caused the posterisation.

    You have limited information which it is best to expose correctly to begin with.
     

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