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Measuring white but has a cast nonetheless

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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 20, 2009
    rutt wrote:
    Looks much better, NeiL. Don't you agree. For fixing this kind of cast, RGB curves in a color blend layer is probably what you want. LAB is great, and can fix much worse casts quickly, but these days I always start out doing just this to fix minor casts.

    BTW, adjustments to the blue curve don't tend to impact contrast, but the other channels do. It's a good habit to use a color blend layer to ensure that all you change is color not contrast.


    I can live with it!mwink.gifD Seriously, yes, I do think it does look much better.

    Yes, I used the color blend mode for the blue curve adjustment. In fact I used two layers of the blue curve adjustment (at a lower original amount than you did), with masking, and fade and opacity tuning. Before doing the curves I used Nik's graduated neutral density filter on the very top third of the sky. Before that I used Nik's remove color cast plugin, and before that again I used a technique of justthorne to increase contrast and pop.

    So, sophisticated in its own way, certainly not a one-slide-one-click job.
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 20, 2009
    Guys, I want to know if using LAB in this kind of work is more protective of pixel quality. Does it result in filling and strengthening the histogram rather than tearing it apart and degrading it?

    rutt, it would seem you are becoming/have become a serious LABite. What's in it for you, and what was your way into LAB? I'm hunting for the best primer.

    I will always do careful one-off kinds of pics rather than mass production, so I am resigned to spend the time and effort on post work, whatever techniques I might be using.

    Thanks.
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    ruttrutt Registered Users Posts: 6,511 Major grins
    edited June 20, 2009
    NeilL wrote:
    rutt, it would seem you are becoming/have become a serious LABite. What's in it for you, and what was your way into LAB? I'm hunting for the best primer.

    Thanks.

    Everything I know and how I found it out is here.
    If not now, when?
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    arodneyarodney Registered Users Posts: 2,005 Major grins
    edited June 20, 2009
    NeilL wrote:
    Guys, I want to know if using LAB in this kind of work is more protective of pixel quality.

    Its always less but it depends on the original color space and the bit depth. Every time a conversion to LAB is produced, the rounding errors and severe gamut mismatch between the two spaces can account for data loss, known as quantization errors. The amount of data loss depends on the original gamut size and gamma of the working space. For example, if the working space is Adobe RGB, which has 256 values available, converting to 8-bit LAB reduces the data down to 234 values. The net result is a loss of 22 levels. Doing the same conversions from ProPhoto RGB reduces the data to only 225 values, producing a loss of 31 levels.

    Bruce Lindbloom, a well-respected color geek and scientist, has a very useful Levels Calculator, which allows you to enter values to determine the actual number of levels lost to quantization (see the “Calc page” at http://www.brucelindbloom.com). If you do decide to convert into and out of LAB, do so on a high-bit (16-bit per channel) document.

    If you start with a high bit, wide gamut RGB space in your raw converter, there's no data loss at this point because the demosicing process (Raw to this color space) is the first time the RGB pixels are generated from Raw. So doing as much as possible at this stage is both faster and totally non destructive. Its also vastly more flexible because you're just building metadata instructions for subsequent rendering of this new data (and you have in products like Lightroom, unlimited History). Render the best possible data for Photoshop work, resulting, at least for me, a total lack for the use of Lab.
    Andrew Rodney
    Author "Color Management for Photographers"
    http://www.digitaldog.net/
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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 20, 2009
    rutt wrote:
    Everything I know and how I found it out is here.

    Appreciate it very much!thumb.gif
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 20, 2009
    arodney wrote:
    Its always less but it depends on the original color space and the bit depth. Every time a conversion to LAB is produced, the rounding errors and severe gamut mismatch between the two spaces can account for data loss, known as quantization errors. The amount of data loss depends on the original gamut size and gamma of the working space. For example, if the working space is Adobe RGB, which has 256 values available, converting to 8-bit LAB reduces the data down to 234 values. The net result is a loss of 22 levels. Doing the same conversions from ProPhoto RGB reduces the data to only 225 values, producing a loss of 31 levels.

    Bruce Lindbloom, a well-respected color geek and scientist, has a very useful Levels Calculator, which allows you to enter values to determine the actual number of levels lost to quantization (see the “Calc page” at http://www.brucelindbloom.com). If you do decide to convert into and out of LAB, do so on a high-bit (16-bit per channel) document.

    If you start with a high bit, wide gamut RGB space in your raw converter, there's no data loss at this point because the demosicing process (Raw to this color space) is the first time the RGB pixels are generated from Raw. So doing as much as possible at this stage is both faster and totally non destructive. Its also vastly more flexible because you're just building metadata instructions for subsequent rendering of this new data (and you have in products like Lightroom, unlimited History). Render the best possible data for Photoshop work, resulting, at least for me, a total lack for the use of Lab.

    Excellent comment, Andrew.

    If I read it correctly, in your opinion all the basic and major adjustments are best done at the RAW conversion stage (which is in DPP for me), and then passed to PS (where for me the color space would be sRGB, and @ 16bit) for more particular-purpose processing. And that a successful result at the end of all that will mean there is no need to use LAB. Am I correct?
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    arodneyarodney Registered Users Posts: 2,005 Major grins
    edited June 20, 2009
    NeilL wrote:
    Excellent comment, Andrew.

    If I read it correctly, in your opinion all the basic and major adjustments are best done at the RAW conversion stage (which is in DPP for me), and then passed to PS (where for me the color space would be sRGB, and @ 16bit) for more particular-purpose processing. And that a successful result at the end of all that will mean there is no need to use LAB. Am I correct?

    That's my story and I'm sticking to it...

    As for sRGB 16-bit, fine with the bit depth but I'm not sure sure I'd do all this processing only to end up in sRGB:
    http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf
    Andrew Rodney
    Author "Color Management for Photographers"
    http://www.digitaldog.net/
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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 20, 2009
    arodney wrote:
    That's my story and I'm sticking to it...

    As for sRGB 16-bit, fine with the bit depth but I'm not sure sure I'd do all this processing only to end up in sRGB:
    http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

    Gotcha!thumb.gif
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited June 21, 2009
    @ Andrew
    What's the damage going from DPP RAW to PS ProPhoto to TIFF/JPEG sRGB? Seems to me not much good garnering all the thrills of ProPhoto only to suffer the spills of the later conversions. I think I'd rather sacrifice some gamut for better quality pixels. ne_nau.gif

    Also, I have ProPhoto in my CS3 working color menu. Has that been superseded? Do color spaces go out of date?

    Thanks!
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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    arodneyarodney Registered Users Posts: 2,005 Major grins
    edited June 21, 2009
    NeilL wrote:
    What's the damage going from DPP RAW to PS ProPhoto to TIFF/JPEG sRGB? Seems to me not much good garnering all the thrills of ProPhoto only to suffer the spills of the later conversions. I think I'd rather sacrifice some gamut for better quality pixels. ne_nau.gif

    Its not a damage issue, its an issue of tossing away colors your capture device is able to record and your output device is able to output that exceeds, in some cases greatly, the sRGB color space.
    http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

    http://www.ppmag.com/reviews/200509_rodneycm.pdf
    http://www.ppmag.com/reviews/200510_rodneycm.pdf
    Andrew Rodney
    Author "Color Management for Photographers"
    http://www.digitaldog.net/
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