Dan Margulis and his curves Philosophy...need help

[Andymania]

Why would a RIP ignore it?????

[andrewrodney]

Originally Posted by Andymania

Why would a RIP ignore it?????

Depending on the RIP, it can be setup to see and use the profile or ignore it. Really, really old RIP’s would sometimes crash if they encountered a profile but this is hardly something I’d expect to see in the 21st century. But there was a time when old timers would recommend one not embed a profile for this reason. I suspect Dan ran into this and maybe that is why he suggests it.

There is another reason to keep files untagged. Say you have 300 images going into a book, all in output CMYK ready for print. Each profile could be 2mb in size. You’re talking 600mb to define CMYK numbers that you could just tell someone about. The data is in output color space so hopefully the RIP or other people in the chain will simply send the numbers, as is, to the output device. The profile in this case provides no benefit although I’m just opposed to providing untagged RGB or CMYK mystery meat to just anyone. If I knew for a fact that no one would open and view, edit or alter the data going to the printer, the profiles are not necessary. But if anyone needs to understand what the numbers mean, they need a profile.

[Andymania]

Oh wait.....you mean embedding a profile increases a file size?????? I didn't know that lol.

But wouldn't each image from the 300 have it's own CMYK values? How can one set of CMYK values be used to define the color of all 300 images??

AHHH....I see. Embedding a profile is useful only if the next person might alter it in some way, shape or form.

[Andymania]

Well hold on...another question. If I'm working in an Adobe 1998 or Prophoto RGB working space, then one would have to be certain that whoever receives the file has to be working in those spaces as well right? Or I should I know beforehand what working space the person who is going to receive the file is working in and set my space to his......I'm a little confused on this.

I never did understand the "convert to current working space option" in Photoshop. I thought the whole point of color management is to have consistent color from the time one pushes the shutter button to the time it gets on paper........why would you convert?

[andrewrodney]

Originally Posted by Andymania

But wouldn't each image from the 300 have it's own CMYK values?

They might but the values are being described by a single profile. The profile describes the output conditions (the press for example). So 300 images, piles of CMYK values, one profile.

AHHH....I see. Embedding a profile is useful only if the next person might alter it in some way, shape or form.

The profile defines the scale of the number. Just as telling you we are 300 miles apart gives you information that simply saying “300” does not.

If I'm working in an Adobe 1998 or Prophoto RGB working space, then one would have to be certain that whoever receives the file has to be working in those spaces as well right?

Correct. Giving someone ProPhoto and they assume sRGB (or anything but ProPhoto) would be BAD. That is why you have to embed the profile.

I never did understand the "convert to current working space option" in Photoshop.

NOT a good setting in the Photoshop Color Settings. It forces a conversion from the original color space to whatever color space a user has selected in those Color Preferences.

[Andymania]

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?

[andrewrodney]

Originally Posted by Andymania

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.

[capice]

Another interresting read...but it goes to deep into for me so i just keep on reading

[jhr]

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)?

[RobertAsh]

Originally Posted by Andymania

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.

Originally Posted by Andymania

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.

[RobertAsh]

Originally Posted by Andymania

...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?

Originally Posted by andrewrodney

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....).

[Pictus]

Originally Posted by RobertAsh

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/

[andrewrodney]

Originally Posted by RobertAsh

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

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.

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 isn’t 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% don’t, but that 10% does fit in ProPhoto, don’t you want to send that to the printer?

If you have a wider gamut space and convert to a smaller gamut working space, you’ve clipped. If you start with a wider gamut space and convert to a smaller gamut output space, you’ve clipped (actually you now have two possible rendering intents at your disposal, with a working space to working space conversion you don’t have Perceptual). So I don’t see the point in going ProPhoto to Adobe RGB to output, I’d 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.

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 “if X doesn’t do something right than...” If something isn’t right, it isn’t 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.

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 it’s effect on gamut into account. All output profiles do.

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 can’t see it, even on my wide gamut NEC. True, I could edit colors I can’t see (there are tricks to avoiding this to some degree). But clip printable colors because the display can’t show them? That isn’t the reason I’m 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.

[RobertAsh]

Originally Posted by Pictus

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.

[Andymania]

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