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Dan Margulis and his curves Philosophy...need help

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  #21  
Old 04-21-2012, 07:51 PM
Andymania Andymania is offline
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Re: Dan Margulis and his curves Philosophy...need

Thanks a bunch Andrew. I feel like I know so much more that I can write my own book on color management.

BTW, I'm using an HP laptop that is several years old. Is there a way I can find out how large of a color gamut my display can show?

Lastly, Is it true I should stay away from using ProPhoto RGB as my working space and stick with Adobe 1998 instead since there are very few printers who can print from ProPhoto?
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  #22  
Old 04-21-2012, 10:02 PM
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Re: Dan Margulis and his curves Philosophy...need

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Originally Posted by Andymania View Post
Lastly, Is it true I should stay away from using ProPhoto RGB as my working space and stick with Adobe 1998 instead since there are very few printers who can print from ProPhoto?
Not really. Lots of newer, modern ink jet printers have gamuts that are wider in some areas than Adobe RGB (1998). But not ProPhoto. So if you use Adobe RGB (1998), you clip those colors but not if you were working in ProPhoto. That is the reason for such a wide gamut space.
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  #23  
Old 04-22-2012, 11:42 AM
capice capice is offline
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Re: Dan Margulis and his curves Philosophy...need

Another interresting read...but it goes to deep into for me so i just keep on reading
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  #24  
Old 04-23-2012, 05:05 AM
jhr jhr is offline
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Re: Dan Margulis and his curves Philosophy...need

Hi guys! A very interesting read!

Any opinions on working with eciRGB v2? What would be the benefits/downsides with working with that profile instead of, lets say, Adobe RGB (1998)?

Last edited by jhr; 10-08-2012 at 01:39 AM.
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  #25  
Old 04-24-2012, 09:19 AM
RobertAsh RobertAsh is offline
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Re: Dan Margulis and his curves Philosophy...need

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Originally Posted by Andymania View Post
Thanks guys for the input. But I am still fumbled about this. Dan in chapter 2 of "Professional Photoshop" talks about contrast. He shows several before and after pics as well as the different individual RGB curves that he used to make the after version. Now he used 3 different S curves for each individual channel. I noticed that there wasn't a hue shift either. But those 3 individual channel curves would probably produce the same result as one modified curve in the master composite. So why bother? ( I know you guys mentioned he is from the CMYK generation, but why use the same principle for RGB?)
It probably has to do with the way he's used to working and the degree of control you want. I struggled with RGB curves earlier and then read Dan Margulis' LAB Color book. Since then I've wondered "why would anyone use RGB when you can make adjustments in LAB so much more easily and precisely?" With LAB you can adjust half a curve instead of multiple RGB curves. That is so much easier for me. I'm learning better how to work with RGB curves but LAB overall is still a lot easier for me, makes more sense and is more intuitive. Plus now I'm used to it.

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Originally Posted by Andymania View Post
He also talks about white point and how the camera automatically sets the white point to specular highlights when the white point should be the lightest significant part of the image. Now I wonder again. If I am doing color correction, shouldn't technically the whitest part of the image be the specular highlight since I KNOW that for a fact that speculars should equal R=255 G=255 B=255? I tried setting white point with the white eye dropper tool in curves to something a single tone darker than the specular and it just blew out my highlights. So I have no idea what Dan is talking about in this case.
I wouldn't worry about the speculars. Your white point should be set for the brightest highlight where you want to retain detail. The speculars should fall into place at 255/255/255 by themselves if you set the brightest detail areas correctly. If the brightest highlight where you want to retain detail is a neutral (i.e. a white) then as a start you could try a value between 242/242/242 and 250/250/250 depending on your output media or device.
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  #26  
Old 04-24-2012, 09:21 AM
RobertAsh RobertAsh is offline
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Re: Dan Margulis and his curves Philosophy...need

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Originally Posted by Andymania View Post
...Lastly, Is it true I should stay away from using ProPhoto RGB as my working space and stick with Adobe 1998 instead since there are very few printers who can print from ProPhoto?
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Originally Posted by andrewrodney View Post
Not really. Lots of newer, modern ink jet printers have gamuts that are wider in some areas than Adobe RGB (1998). But not ProPhoto. So if you use Adobe RGB (1998), you clip those colors but not if you were working in ProPhoto. That is the reason for such a wide gamut space.
That's very interesting. Can you share a few makes/models of printers that have wider color gamut than Adobe RGB? Would like to take a look at them. How can one determine the gamut of a specific printer?

Also, as practical matter it's correct that one shouldn't stay away from ProPhoto RGB as one's working color space, but unfortunately it may well still be necessary to Edit > convert to profile > Adobe RGB before printing. If your image has colors in it that are beyond the gamut of your printer but within the gamut of Prophoto RGB, then those colors have to be mapped/compressed/rendered into the printable gamut for the printer. If the printer/paper profile doesn't do it right for those colors then converting the profile to Adobe RGB at least gives you a more controllable, predictable set of colors to output.

Finally, the paper or other printable medium has a gamut range as well, typically smaller than the printer's or monitor's. So one is limited by the smallest gamut amongst the printing elements (monitor, printer, ink, paper or other printable medium). But working in ProPhoto is best because those elements do improve (some faster than others....).
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  #27  
Old 04-24-2012, 10:43 AM
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Re: Dan Margulis and his curves Philosophy...need

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Originally Posted by RobertAsh View Post
That's very interesting. Can you share a few makes/models of printers that have wider color gamut than Adobe RGB? Would like to take a look at them. How can one determine the gamut of a specific printer?
In http://www.iccview.de/content/view/3/7/lang,en/ we can compare
color spaces, monitor and printer profiles, this plug-in is needed
http://www.iccview.de/content/view/1/5/lang,en/
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  #28  
Old 04-24-2012, 11:52 AM
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andrewrodney andrewrodney is offline
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Re: Dan Margulis and his curves Philosophy...need

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Can you share a few makes/models of printers that have wider color gamut than Adobe RGB?
Here is one area within 3D of Adobe RGB (1998) versus an Epson 7900 with Luster paper:

http://digitaldog.net/files/ARGBvs7900.jpg

Quote:
Also, as practical matter it's correct that one shouldn't stay away from ProPhoto RGB as one's working color space, but unfortunately it may well still be necessary to Edit > convert to profile > Adobe RGB before printing.
Going from ProPhoto to Adobe RGB (1998) to a print output device is going to introduce another conversion in the loop and is less direct in terms of a conversion. Keep in mind that currently implementing a conversion, the actual source of the color space is not defined (that is one thing V4 profiles with what is called the PRMG allows). By the time the Epson profile in this case comes into play, it is feed Lab data. It is ProPhoto to Lab to Epson. Or in your example, ProPhoto to Lab>Lab to Adobe>Adobe to Lab>Lab to Epson.


Quote:
If your image has colors in it that are beyond the gamut of your printer but within the gamut of Prophoto RGB, then those colors have to be mapped/compressed/rendered into the printable gamut for the printer.
It isnít quite that simple in terms of colors in or out of gamut. As you can see in the 3D map above, there are colors that fall outside Adobe RGB and those that do not. If a small portion of say Blue (important for printing an image with sky) is out of printer gamut in Adobe RGB but not ProPhoto, but the opposite might be true with other colors, what do you except for clipping? The size and shape of RGB working space are simple and predictable but output spaces are not. If 90% fits into Adobe RGB and 10% donít, but that 10% does fit in ProPhoto, donít you want to send that to the printer?

If you have a wider gamut space and convert to a smaller gamut working space, youíve clipped. If you start with a wider gamut space and convert to a smaller gamut output space, youíve clipped (actually you now have two possible rendering intents at your disposal, with a working space to working space conversion you donít have Perceptual). So I donít see the point in going ProPhoto to Adobe RGB to output, Iíd go directly from ProPhoto to output and pick a rendering intent that clips fully or clips and remaps other colors (Perceptual). One less conversion, one more rendering intent to try.

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If the printer/paper profile doesn't do it right for those colors then converting the profile to Adobe RGB at least gives you a more controllable, predictable set of colors to output.
I read a lot of statements here about ďif X doesnít do something right than...Ē If something isnít right, it isnít right. Generally speaking, we hope to be using good output profiles. Anything less is suboptimal. The question is really, do you encode within a color space that clips colors you captured and can print or do you throw them away. My suggestion is to keep the colors.

Quote:
Finally, the paper or other printable medium has a gamut range as well, typically smaller than the printer's or monitor's.
The paper affects the gamut. But the output gamut, as shown here to my Epson with Luster paper takes that paper, and itís effect on gamut into account. All output profiles do.

Quote:
So one is limited by the smallest gamut amongst the printing elements (monitor, printer, ink, paper or other printable medium). But working in ProPhoto is best because those elements do improve (some faster than others....).
Yes and no. So you have a capture device that has a gamut that exceeds the display. And much more of that data (but not all) can be printed. Unless the final output is a display, I see little reason to use a smaller space because of the limitations of the display gamut. True, I canít see it, even on my wide gamut NEC. True, I could edit colors I canít see (there are tricks to avoiding this to some degree). But clip printable colors because the display canít show them? That isnít the reason Iím using a 10 color ink jet. One is limited by the smallest gamut to some degree and fully when the output device (which is often undefined and changes over time) is a fixed and small gamut.
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  #29  
Old 04-24-2012, 02:53 PM
RobertAsh RobertAsh is offline
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Re: Dan Margulis and his curves Philosophy...need

Quote:
Originally Posted by Pictus View Post
In http://www.iccview.de/content/view/3/7/lang,en/ we can compare
color spaces, monitor and printer profiles, this plug-in is needed
http://www.iccview.de/content/view/1/5/lang,en/
Pictus,

Thanks, this is a great resource.
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  #30  
Old 04-26-2012, 01:58 PM
Andymania Andymania is offline
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Re: Dan Margulis and his curves Philosophy...need

Good stuff guys. Robert, I have his Lab color book and am going to read it next.
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