Re: ProPhoto RGB or Adobe RGB 1998
Re: ProPhoto RGB or Adobe RGB 1998
- Subject: Re: ProPhoto RGB or Adobe RGB 1998
- From: Neil Barstow <email@hidden>
- Date: Sun, 25 Jan 2004 17:20:20 +0000
Hi Doug
email@hidden (Doug Walker)::25/1/04::3:20 pm:: GMT-0800
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On Sunday, January 25, 2004, at 02:37 AM, Neil Barstow wrote:
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> test
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Hi Neil,
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Thanks for note. I am game but remember, I am humbly a novice in high
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dudgeon.
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> make a Granger Rainbow in a reasonable space like Adobe RGB (1998). [or
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> find one and <assign profile> the Workingspace]
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Done, I presume that this is simply a long horiz new RGB image in
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AdobeRGB that I create a rainbow gradient from left to right. Named
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A.psd
no, square doc usually
it's not just a rainbow
make new doc, set profile to Adobe RGB.
first make a spectrum (there's a default gradient) in the base layer
then make a new empty layer. In the new layer make a black to white
gradient across the axis of the other grad, now set new layer blend
mode to luminosity. flatten.
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> duplicate the image
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Done by actual Duplicate in system renamed B.psd, not New Document
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right?
yep duplicate
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> copy A
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> now in photosop try setting custom softproofing to the sRGB space
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Done, with RelCol not Perceptural right (is this the point that it is
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RelCol in profile to profile no matter what you choose?).
yes, at this stage that's right, it depends on the profile types. there
is no difference here betweeen relcol and Per. that's what we are
proving
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And w/no
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Preserve Color Numbers checked, right?
yes
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> copy A
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> invoke and observe gamut warning, leave this window up
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Done, All is should see is out of gamut grey, right?
yep
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> copy B
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> look at the levels histogram
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> depress the alt key to reveal the clipping and mouse click on one of
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> the input arrows.
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Done, smooth canoe-shaped histogram left to right. Click left input
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arrow, all I see are 3 rectangular c,m and y sections with 3 thin
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spikes of r, g, and blue. Right? Click right input arrow, all I see
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are 3 rectangular r, g, and b squares with 3 thin spikes of c, m, and
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y. Right?
yep, no clipped colour detail
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So these extremes show where the cut off occurs? What am I discerning
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here.
yep
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> copy B
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> convert the ARGB image to the sRGB space
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Done. Hope my default setting doesn't throw this off.
use >image mode convert to profile.
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This pane came
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up w/Perceptual defaulted but I changed it to RelCol for sake of
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consistency. If that is wrong let me know.
fine
try perceptiual too
we are proving theres no difference here
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> copy B
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> look at the levels histogram, post conversion
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In the image I see less banding in the green area...read smoother
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transition than before convert.
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However, I see only a little change in the histogram. Am I missing
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something? Maybe a little taller spike in the left input side.
next step is relevant one
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> copy B
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> depress the alt key to reveal the clipping and mouse click on one of
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> the input arrows.
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Lots more green is the difference between before converting and after.
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Before there was basically c, m, and y but now I get some green in
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there when clicking on the left input holding the option key. And when
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I <commandb" shit b" y> I see a wide band of yellow/marigold color left
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UN-greyed, not before the convert. Does that mean that yellow is now
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in Gamut?
lots of colour detail has been clipped
the gamut warning overlay shows where
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How does this all translate into everyday workflow. (read not quite
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congealed) And where is ProPhoto RGB in all this?
well, if clipping's a problem converting between 2 Adobe spaces you can bet
pro photo is worse. A longer more complex test wouild demonstrate that.
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How does this wend its way into choosing an output space.
its a long answer
use colorthink to get you started, plot the image data [profile embedded]
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Thanks for the running exercise. Looking forward to your thoughts.
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Doug Walker, FP
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"Specializing in People on Location in a Clean, Bold Classic Style!"
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website: http://www.walkerphoto.com
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Member, ASMP, APA SF
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Regards, NeilB. Apple Solutions Expert
colourmanagement.net :: Consulting in Imaging & Colour Management
custom profiling, training, implementation, seminars,
resell:: Gretag+eyeOne. basICColor Display etc. XRite. GTI viewing booths
www.colourmanagement.net/ :: www.apple.com/uk/creative/neilbarstow/
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