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Author Topic: color shift between ProPhoto and sRGB  (Read 3981 times)

wmchauncey

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color shift between ProPhoto and sRGB
« on: February 24, 2015, 03:51:06 pm »

It's relatively easy to check colors between ProPhoto and sRGB by using the color sampler tool.

Is there any way to quantify levels of saturation of a particular color?     ???
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digitaldog

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Re: color shift between ProPhoto and sRGB
« Reply #1 on: February 24, 2015, 03:52:18 pm »

Histogram.
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wmchauncey

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Re: color shift between ProPhoto and sRGB
« Reply #2 on: February 24, 2015, 04:15:06 pm »

Andrew, you're not preaching to the choir here...how does the histogram give numerical amounts to saturation?
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digitaldog

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Re: color shift between ProPhoto and sRGB
« Reply #3 on: February 24, 2015, 05:13:14 pm »

Andrew, you're not preaching to the choir here...how does the histogram give numerical amounts to saturation?
The only way to get numeric values is bring the colors into something like ColorThink Pro and plot em. The Histogram is still very valuable in showing you what encoding space will or will not clip colors.
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Tim Lookingbill

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Re: color shift between ProPhoto and sRGB
« Reply #4 on: February 24, 2015, 09:57:28 pm »

I always thought going by the color managed preview was helpful enough seeing that there is an inconsistency between luminance levels across a wide range of hues depending on which saturation increasing slider is used. I saw it happen with Erik's landscape image jpeg in the Coffee Corner forum where I applied a +20 saturation increase in both sRGB and ProPhotoRGB and only the sunlit green hills increased in luminance and the other colors like the blue sky didn't-(in Photoshop-doesn't happen in ACR/LR). How do you quantify that?

Clipping in the histogram will give a good enough indicator if those clipped colors due to over saturation will shift in a print when Soft Proofing. But I've found there's the same inconsistencies there as well, so quantifying it isn't going to make for a consistent predictor on whether the image is improving or becoming a mess on a print.

If you could tell us why you want to quantify saturation levels we could provide better information.
« Last Edit: February 24, 2015, 10:24:34 pm by Tim Lookingbill »
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wmchauncey

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Re: color shift between ProPhoto and sRGB
« Reply #5 on: February 27, 2015, 07:47:48 am »

My initial query was to determine a way to replicate saturation, except by eye, when one alters color space.
I normally work in ProPhoto until I save an image, in sRGB, for print or web display.
Altering the luminous RGB numbers is easy but matching saturation is more of a subjective thing and that presents the enigma.
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Tim Lookingbill

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Re: color shift between ProPhoto and sRGB
« Reply #6 on: February 27, 2015, 01:22:21 pm »

My initial query was to determine a way to replicate saturation, except by eye, when one alters color space.
I normally work in ProPhoto until I save an image, in sRGB, for print or web display.
Altering the luminous RGB numbers is easy but matching saturation is more of a subjective thing and that presents the enigma.

I may not be understanding your issue since there shouldn't be a change to saturation when converting from ProPhotoRGB to sRGB for web viewing unless you're talking about viewing the sRGB tagged image online in a browser that's not color managed.

Now, I have seen slight hue/sat shifts of certain saturated colors like intense greens, yellows, blues and light oranges converting from ProPhotoRGB to sRGB but only on my display. The only remedy was to convert to my "sRGB-ish" custom ColorMunki display profile so only I can see it.

It's impossible for me to see this on any other display used for web browsing because I don't view the web on smartphones, tablets or off the shelf non-calibrated computer systems. I only use my calibrated display.

I have viewed my images on a 98% AdobeRGB gamut Samsung AMOLED Tablet hooked to wifi at Best Buy, but the hue/sat was so off that attempting to match it was pointless. Even switching to Basic Mode that's suppose to track colors to sRGB using the Samsung's Adaptive settings was still off but not as much as Cinema and Photo Mode. The color temperature played a major role in preventing a better color match in Basic mode.
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D Fosse

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Re: color shift between ProPhoto and sRGB
« Reply #7 on: February 27, 2015, 02:14:58 pm »

My initial query was to determine a way to replicate saturation, except by eye, when one alters color space.
I normally work in ProPhoto until I save an image, in sRGB, for print or web display.
Altering the luminous RGB numbers is easy but matching saturation is more of a subjective thing and that presents the enigma.

Not so easy in RGB because saturation is relative to the color space. A saturated color in sRGB is not very saturated in PP.

However, Lab numbers are absolute and independent from the RGB space the file is in. The numbers for the a and b channels will be the same in both, assuming no clipping.

(I have to confess I'm not really sure what you're looking for).

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Simon Garrett

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Re: color shift between ProPhoto and sRGB
« Reply #8 on: February 27, 2015, 02:16:25 pm »

I may not be understanding your issue since there shouldn't be a change to saturation when converting from ProPhotoRGB to sRGB for web viewing unless you're talking about viewing the sRGB tagged image online in a browser that's not color managed.

Are you sure about that?  Assuming the colours are within sRGB gamut (so don't get clipped), the same colour will have a higher saturation value when converted to sRGB than in ProPhoto RGB.  

For example (in this case going from sRGB to ProPhoto RGB for my convenience), this image is sRGB, with all colours 100% saturation:


But if I load into Photoshop and convert to ProPhoto RGB, the saturations are much lower.  The red patch saturation goes to 85%, the green to 67% and so on.  The colours don't change on the screen, obviously, but the numerical values of saturation are lower. 

Or am I misunderstanding you?   ???  ???
« Last Edit: February 27, 2015, 02:46:12 pm by Simon Garrett »
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Tim Lookingbill

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Re: color shift between ProPhoto and sRGB
« Reply #9 on: February 27, 2015, 03:41:34 pm »

So you're going by numbers to assess saturation rather than previews in a color managed environment?

We've been down that road starting in Photoshop 5 when color management was first introduced where it said the numbers don't matter any longer, just the preview at least as it's applied to photography. Graphic design folks may have issues but I've not heard of any yet. 

Why do the numbers concern you? Are you doing some kind of color science analysis project and require some kind of control standard or color ground zero to study saturation by the numbers?

 
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digitaldog

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Re: color shift between ProPhoto and sRGB
« Reply #10 on: February 27, 2015, 06:33:38 pm »

So you're going by numbers to assess saturation rather than previews in a color managed environment?
Seems that would work far better, especially for any evaluated colors that fall outside display gamut no?
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We've been down that road starting in Photoshop 5 when color management was first introduced where it said the numbers don't matter any longer, just the preview at least as it's applied to photography.
It (who) said that (the numbers don't matter any longer)?
FWIW, color management in applications dealing with color existed before Photoshop 5. ColorBlind as one example by several years.
Numbers are often unambiguous, certainly when dealing with colorimetry! In some work, the less subjectivity the better.
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BobShaw

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Re: color shift between ProPhoto and sRGB
« Reply #11 on: February 27, 2015, 07:09:25 pm »

I normally work in ProPhoto until I save an image, in sRGB, for print or web display.
If you save in sRGB for printing then to me you wasted the whole purpose of using ProPhoto. You may as well have used sRGB from the start.
My entire workflow is AdobeRGB and that is what I print from. Aperture or whatever you use converts to sRGB JPG for web.


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wmchauncey

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Re: color shift between ProPhoto and sRGB
« Reply #12 on: February 27, 2015, 08:42:52 pm »

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So you're going by numbers to assess saturation rather than previews in a color managed environment
You to, my friend, will someday be old with inadequate vision.
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Numbers are often unambiguous, certainly when dealing with colorimetry! In some work, the less subjectivity the better.
Suits my left sided brain quite well.
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Tim Lookingbill

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Re: color shift between ProPhoto and sRGB
« Reply #13 on: February 28, 2015, 12:36:17 am »

You to, my friend, will someday be old with inadequate vision.Suits my left sided brain quite well.

It would've helped if you specified that. How are any of us to know you have vision issues with judging saturation through a preview?

I can't help you, sorry. Maybe others here will pitch in and offer some solutions.
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