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Author Topic: Basic Color Space Question  (Read 5603 times)
Dave Gurtcheff
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« on: June 20, 2009, 04:37:18 PM »
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I have always used Adobe RGB as my color space for editing my photos in Photoshop. My monitor is profiled, and the agreement between my prints and monitor has been OK. After printing, I usually down size to 72dpi, change to 8 bits, and save as a JPG and post on my web site, or add to a digital slide show. I recently changed to Prophoto RGB for my color space, and again the correlation between monitor and printsd is OK, but when down-sizing and saving as a JPG for web/slide show the colors are muted and off color. Should I stick to Adobe RGB in order to be able to both make prints and still be able to use for web?
Thanks in advance  
Dave Gurtcheff
www.modernpictorials.com.
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Mark D Segal
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« Reply #1 on: June 20, 2009, 05:09:40 PM »
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Dave,

The main culprit here may be that in saving the JPEG version for your website you did not use "Save for Web and Devices" and did not make sure to select both sRGB colour space AND Black Point Compensation. With this combo the web images should be good.

Mark
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
Brian Gilkes
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« Reply #2 on: June 20, 2009, 05:24:25 PM »
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Don't forget to allow for increase in average monitor resolution. There is nothing sacred about 72dpi. Last year 90 was a better bet. This year 100.
As far as colour spaces go Prophoto RGB and sRGB are pretty average too and fast dropping below average. It's a bit like the qwerty key board , originally designed to slow typists down so the mechanical keys on typewriters didn't jam.  Once a system is in place no one wants to change it even when the technology it was designed for no longer exists or has radically changed.
Brian
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Mark D Segal
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« Reply #3 on: June 20, 2009, 05:32:40 PM »
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Resolution between a range of 72 to over 100 PPI has nothing to do with Dave's problem and will not affect image appearance on the web. In fact saving to a lower resolution is a better deterent in respect of  copyright infringement. Also there has been no radical change of technology which I know of pointing to the use of anything other than sRGB for saving an image to be posted on the internet.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
MPatek
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« Reply #4 on: June 20, 2009, 10:23:59 PM »
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Dave,

as others already pointed out, it is about displaying your jpeg images with RGB values optimized in ProPhoto RGB space. Conversion to sRGB color space is needed to recalculate (map) RGB values for smaller sRGB color space (actual RGB values are different between two color spaces). Moreover, ProPhoto is built on gamma 1.8 while sRGB and Adobe RGB spaces are set for gamma 2.2. If web images are not displayed through a color managed browser, sending ProPhoto images to common displays (LCD, CRT) leads to noticeable color distorsions. Images appear washed out and brighter.
What is not clear to me is that you do not mention converting AdobeRGB images into sRGB color space before posting them on web. Unless you (and those who look at your images) do not have a wide-gamut monitor, images should still appear slightly off. I have made a comparison just for this exact case. See, Editing images in the Adobe RGB color space.

Marcel

www.marcelpatek.com
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Marcel

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Brian Gilkes
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« Reply #5 on: June 21, 2009, 07:25:42 AM »
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Hi Mark,
I agree sRGB is fine for web.
For printing, Adobe RGB may not be optimum. ProPhoto RGB does not have the best  luminosity steps and it's mapping of some colours eg blue /cyan is not the best. Adobe RGB does not include many colours capable of being printed on current printers.
I'm inclined towards Joe Holmes spaces, but reckon we may see some more that will work better in the rapidly changing environment. Most problematic is the way in which Perceptual Rendering is mapped.
It's early days.
Cheers,
Brian
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bjanes
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« Reply #6 on: June 21, 2009, 08:13:47 AM »
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Quote from: Dave Gurtcheff
I have always used Adobe RGB as my color space for editing my photos in Photoshop. My monitor is profiled, and the agreement between my prints and monitor has been OK. After printing, I usually down size to 72dpi, change to 8 bits, and save as a JPG and post on my web site, or add to a digital slide show.

Mark has answered your question regarding your color problems. Digital images consist of pixels and their dimensions are reported in terms of pixels. Only after a lateral dimension (in inches or centimeters) has been assigned is there a meaningful resolution in terms of pixels per inch. Alternatively, one can assign the resolution in terms of pixels per inch, and the dimensions in terms of inches will be set. These relationships are shown on the Photoshop Image Size dialog shown below. If one is saving images for the web, it makes sense to constrain the proportions of the image and select either the height or width in pixels.

[attachment=14720:PS_ImageSize.gif]

In the example above, you might choose a height of 800 pixels so that the image would fit on most screens. Photoshop would then adjust the width proportionally as shown. The resolution in pixels per inch depends on the lateral dimension in inches and is not important, since web browsers display the image at 100%. The image size in inches will depend on the size of the monitor as will the resolution in pixels per inch.

[attachment=14721:PS_ImageSize2.gif]

Bill
« Last Edit: June 21, 2009, 08:16:53 AM by bjanes » Logged
Mark D Segal
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« Reply #7 on: June 21, 2009, 09:21:13 AM »
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Quote from: Brian Gilkes
For printing, Adobe RGB may not be optimum. ProPhoto RGB does not have the best  luminosity steps and it's mapping of some colours eg blue /cyan is not the best. Adobe RGB does not include many colours capable of being printed on current printers.

Brian,

Yes, I agree we can now surpass Adobe RGB in prints - happens with my Epson 3800 using Ilford Gold Fibre Silk, and would be all the more the case with the Pro x900 Epsons.

If you have evidence showing there are other wide gamut colour spaces with "better" luminosity gradation and blue/cyan rendition or better Perceptual tone mapping than those of Pro Photo, it would be interesting to see that. As for the R.I., my understanding is that the imaging application performs this and the quality of the rendering depends on the math in Photoshop, or whichever.

Mark
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
Dave Gurtcheff
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« Reply #8 on: June 25, 2009, 09:38:25 PM »
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Thanks all for the input. My wife and I travelled from NJ to Minnesotta to see our grandson graduate from HS; we were out of touch for a week, and I am tardy with my thanks.
Best to all and thanks
Dave
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ITEnquirer
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« Reply #9 on: June 26, 2009, 01:43:40 AM »
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I have been heavily involved in colour management until a year ago. For IT Enquirer, I reviewed the Eye One Pro with iO robot arm, I have ProfileMaker Packaging (a 12000 USD colour measurement and profile creation software that tackles multi-colour aka high-fidelity printing) etc, etc.

As far as I know Profoto RGB is excellent for saving images' colour gamut at their maximum, because it's one of the biggest colour spaces available. AdobeRGB is much smaller --you can check that out with Chromix ColorThink if you want to. It even saves colours the human eye can hardly discern.

What I have understood from the many explanations by colour management experts is that if colour shifts appear it's because colours in your image are in the outer areas of Profoto RGB that are difficult to map to smaller colour spaces like AdobeRGB. sRGB is about the smallest space you can get, so you're bound to see colour shifts.

But I now realise that Marcel Patek has already said what I am saying...
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In a previous life, I was a member of the Bar Association in Antwerp, Belgium.

Currently I am the publisher of IT Enquirer, an information resource for cross-channel publishing processes with an emphasis on the processes from start to finish (including, therefore, photography both commercial and journalistic). http://www.it-enquirer.com
Dick Roadnight
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« Reply #10 on: June 26, 2009, 04:20:24 AM »
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Basic colourspace question:
What is the best colourspace for getting the best out of an Epson 7900/Colorburst/CS4/Phocus/H3D11-50?

I have been told that DCAM is the best - and when I asked which DCAM?, I was told that I had to spend a day learning how to analyze each picture to work out which colour space to use?
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« Reply #11 on: June 26, 2009, 07:35:09 AM »
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Quote from: Dick Roadnight
Basic colourspace question:
What is the best colourspace for getting the best out of an Epson 7900/Colorburst/CS4/Phocus/H3D11-50?

Based on the gamut of that device, ProPhoto RGB if the choices are the big three (sRGB, Adobe RGB (1998) or ProPhoto RGB).
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Andrew Rodney
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Brian Gilkes
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« Reply #12 on: July 01, 2009, 07:21:01 PM »
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Dick,
I use DCam 3 from camera via RAW Developer, and JH Chrome 100 from scans.
Using gamut Check in PS to see if you have clipping . If so use variants to expand the space. If all is included print with Relative Colorimetric. To open shadows use Perceptual.
Mark
As I understand it there are no standard methods of determining Perceptual mapping. This is where a skilled profile builder comes in.  There seems to be trade offs between 'correct colour", viewed under standard conditions and perceived luminosity. The way colours are mixed with the printing inks makes things harder too.
especially now orange and green inks are mixed with CMYK. Then there are RIPs and now what looks like incompatibility between OSX, CS4 and MK on x900 Epsons. Frankly most of this is beyond me , so I rely on the best advise I can get. I am getting ColorThink though . I've seen the differences in mapping between ProPhoto and DCam spaces demonstrated via ColorThink and other programs. This helps a lot to see what is going on , but the human response thing is more difficult. Luminosity and colour clarity is hard to define . There is a difference between papers too. Mould made papers seem to give inks more presence than machine papers.
Some Japanese papers like Awagami Kozo allow light to pass through ink to base paper and it refracts back through the inks . The gamut is smaller than European or US papers but the prints have a sort of life to them -hard to describe. The dragon may fly from the paper.

Je suis dans une maison d'estampes japonaises
Le soleil est partout, car tout est transparent (Annie Duthil)

Cheers,
Brian
www.pharoseditions.com.au

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Dick Roadnight
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« Reply #13 on: July 02, 2009, 05:04:17 AM »
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Quote from: Brian Gilkes
Dick,
I use DCam 3 from camera via RAW Developer, and JH Chrome 100 from scans.
Using gamut Check in PS to see if you have clipping. If so use variants to expand the space. If all is included print with Relative Colorimetric. To open shadows use Perceptual.

I am getting ColorThink though . I've seen the differences in mapping between ProPhoto and DCam spaces demonstrated via ColorThink and other programs. This helps a lot to see what is going on ,
Brian
Thank you very much.
Are "Relative Colorimetric" and "Perceptual" programs, options or what?

ColorThink has been recommended to me: I was thinking about using Dcam 3 for everything and not worrying about it for the time being.

If you spend a few hundred the camera does it all for you, if you spend tens of thousands it takes months to set it up to get the best out of it!
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bjanes
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« Reply #14 on: July 02, 2009, 08:35:18 AM »
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Quote from: Dick Roadnight
Basic colourspace question:
What is the best colourspace for getting the best out of an Epson 7900/Colorburst/CS4/Phocus/H3D11-50?

I have been told that DCAM is the best - and when I asked which DCAM?, I was told that I had to spend a day learning how to analyze each picture to work out which colour space to use?


Even if you don't use Joseph Holmes' DCAM spaces, you can learn quite a bit about color spaces and their application by reading the essays on his web site.

His section Gamut Plots compares them to aRGB and ProPhotoRGB. He is concerned about matching the gamut of the image to that of the space to avoid quantization errors, but admits that these can largely be eliminated by using a bit depth of 16. He points out that aRGB uses a reference white of D65, whereas the PCS (profile connection space) used for most color management is D50. With aRGB one may get errors from chromatic adaption. Also, the gamut is aRGB is not sufficient for some modern printers. ProPhotoRGB uses D50 and is wide gamut, but has a gamma tone curve, which he says becomes too flat near black and is not perceptually uniform. His curves have a perceptually uniform tone curve (i.e. basically L*). Again, this deficiency is largely eliminated at a bit depth of 16.

Bruce Lindbloom discusses these considerations in his proposal for a new color space, BetaRGB. It uses a reference white of D50 and a 2.2 gamma tone curve. To minimize quantization errors, he chose color primaries that include most real world colors. The gamut is not as wide as ProPhotoRGB. He states that a gamma of 2.2 produces smaller ΔEs than the gamma of 1.8 used in ProPhotoRGB. Again if one uses a bit depth of 16, this is likely not significant.

Spaces using an L* tone curve are available, for example eciRGB_V2. It is widely used in Europe, but has not caught on in the USA. I think that the ISO22028-2_ROMM-RGB.icc profile is essentially an updated ProPhotoRGB, but it does not appear to be in widespread use.

In view of the above discussion, I would conclude that 16 bit ProPhotoRGB is the most suitable widely used space for use with wide gamut printers such as your Epson.

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digitaldog
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« Reply #15 on: July 02, 2009, 09:18:41 AM »
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Quote from: bjanes
He points out that aRGB uses a reference white of D65, whereas the PCS (profile connection space) used for most color management is D50.

That's not really relevant unless you insist on using Absolute renderings inappropriately.

Quote
ProPhotoRGB uses D50 and is wide gamut, but has a gamma tone curve, which he says becomes too flat near black and is not perceptually uniform. His curves have a perceptually uniform tone curve (i.e. basically L*). Again, this deficiency is largely eliminated at a bit depth of 16.

Exactly! For 16-bit work, its basically a moot point.

Quote
In view of the above discussion, I would conclude that 16 bit ProPhotoRGB is the most suitable widely used space for use with wide gamut printers such as your Epson.

Sounds perfectly reasonable to me as well, especially if you're working with an Adobe Raw engine which is using ProPhoto primaries anyway.
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Andrew Rodney
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Dick Roadnight
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« Reply #16 on: July 02, 2009, 01:50:41 PM »
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Quote from: digitaldog
Sounds perfectly reasonable to me as well, especially if you're working with an Adobe Raw engine which is using ProPhoto primaries anyway.
Thank you all for your replies... can you not suck a profile into phocus or ACR before the data is lost?
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« Reply #17 on: July 02, 2009, 01:55:53 PM »
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Quote from: Dick Roadnight
Thank you all for your replies... can you not suck a profile into phocus or ACR before the data is lost?

Sorry, I don't understand the question.
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Andrew Rodney
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Dick Roadnight
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« Reply #18 on: July 02, 2009, 02:23:31 PM »
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Quote
Based on the gamut of that device, ProPhoto RGB if the choices are the big three (sRGB, Adobe RGB (1998) or ProPhoto RGB).
Quote from: digitaldog
Sounds perfectly reasonable to me as well, especially if you're working with an Adobe Raw engine which is using ProPhoto primaries anyway.
Quote from: Dick Roadnight
Thank you all for your replies... can you not suck a profile into phocus or ACR before the data is lost?
I was thinking that you were saying that the "ProPhoto primaries" might cause clipping that could not subsequently be rectified by assigning a colourspace... You need to assign a colour space as soon as you can to avoid loosing data?

My original question was about DCAM - are the DCAM colour spaces bigger or better than ProPhoto RGB?
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