Prophoto RGB?

[John Curran]

I was wondering if anyone out there is scanning transparencies using Prophoto RGB, and how they might be using it in their workflow. I am assuming one would capture and color balance in Prophoto and then change the profile right before output?

Thanks

John

[QT Luong]

The Prophoto RBG space is unnecessarily large for scanning transparencies. It holds many more colors than a chrome can. Joseph Holmes Ektaspace is better matched to the color gamut of a chrome. Prophoto is mostly useful for digital captures.

You need to change the color space only if you send out a digital file for printing. If you print on your own printer, it will be converted at the time of printing.

[Gordon Moat]

I have been using the ProPhotoRGB space for most images since about 1999. There can be more room for edits, but also more room for errors. In general, web images get converted to sRGB on output, and print images go to various CMYK spaces as needed.

The idea behind a larger than you need colour space is that there can be less clipping upon conversion to CMYK. However, there can also be a greater risk of having out of gamut colours. As with anything, it can take some practice, and trial and error. Sometimes this choice can work well, and other times it can hinder your results.

You should also compare the native colour space of the scanner to ProPhotoRGB prior to choosing it. You might find that the scanner RGB colour space might offer more accurate CMYK comversion potential. As with any work of this sort, watch your information palette Total Ink, as well as the individual CMYK percentages, and be aware of out of gamut areas. Some high end scanners have a more usable colour space than others, though quite often AdobeRGB can be another good compromise.

Colour management is communicating colour. If your output device is on a desktop and only accepts RGB files, then you might find ProPhotoRGB to be a bad choice in your workflow. You should also be aware that your monitor is merely a simulation of the final print; your goal should be to match your printed output to the chrome, or at least to your scene (unless you like heavily manipulated images); if you only match the print to your monitor, quite often you can be clipping many colours. ProPhotoRGB is not a bad choice, but only if it fits your workflow and output, and recognize that it is not appropriate for all images.

Ciao!

Gordon Moat
A G Studio

[Bruce Watson]

I am assuming one would capture and color balance in Prophoto and then change the profile right before output?

It depends. I haven't tried to burden my old drum scanner with the concept of a working space. What it gives me is an untagged TIFF file (technically I guess it would be in "scanner space"). When I open the file in Photoshop I assign it a working space, typically ProPhoto RGB.

QT is right, it's a big working space. Ektaspace isn't free however, and ProPhoto RGB is in that it ships with Photoshop. What matters most to me is that my working space is bigger than my printer's ICC profile. That is, I want to be constrained by the output ICC profile, not by my working space.

Anyway, I import the file and assign it to ProPhoto RGB, do my cropping and clean up my black and white points, then set up soft proofing using the output ICC profile for the printer/paper/ink I have in mind for the print. All my color corrections, editing, gamut checks, etc. are all done under soft proofing.

So really I'm working (doing all my edits) inside the output ICC profile. The working space is mostly irrelevant as long as it doesn't interfere.

I'm not saying this is the only way to do it, or that it's what people should be doing. I don't claim to be an expert. But this method works fairly reliably for me.

[Walter Calahan]

Adobe 1998 RGB

[QT Luong]

The main problem in working with a large color space is that you have less numerical separation between two given colors than you would have with a smaller color space. When working in Prophoto, it is almost a necessity to use 16bit color. One of the flavors of Ektaspace is free, and enough of an industry standard that drum scan operators in India did not need any explanation about it.

[Stephen Best]

I was wondering if anyone out there is scanning transparencies using Prophoto RGB, and how they might be using it in their workflow. I am assuming one would capture and color balance in Prophoto and then change the profile right before output?

A better space for scans is Bruce Lindbloom's Beta RGB. More details and a free download here:

http://www.brucelindbloom.com/BetaRGB.html

You should also read this:

http://www.brucelindbloom.com/WorkingSpaceInfo.html

Beta RGB is somewhere in size between Adobe RGB and Prophoto RGB. Prophoto RGB will contain everything you can scan but it's a bit coarse for editing (small curve moves result in big changes). Scans I do for others are always Adobe RGB even though I offer a choice (it's not worth the time explaining the differences). Nobody has yet complained. When it comes time to print though it makes no difference which space you use.

Recently I moved my workflow to a custom space which is a hybrid of the chromaticity coordinates and whitepoint (D50) of Beta RGB and the L* gamma of Lstar-RGB. My display is also calibrated to L* (with Basiccolor display 4.1.6, now they've fixed the product for my NEC display). L* gives more separation in shadow values. It's early days but it seems to be working well. For grayscale, my corresponding workspace is QTR - Gray Lab.

Note that Sharma in "Understanding Color Management" recommends leaving the scan in the scanner space. This approach is probably appropriate if you're going to do the bulk of your colour and tonality adjustments in the scanning software. These days I just do a raw unclipped 16-bit scan and most of the work in Photoshop.

[Stephen Best]

Anyway, I import the file and assign it to ProPhoto RGB, do my cropping and clean up my black and white points, then set up soft proofing using the output ICC profile for the printer/paper/ink I have in mind for the print. All my color corrections, editing, gamut checks, etc. are all done under soft proofing.

So really I'm working (doing all my edits) inside the output ICC profile. The working space is mostly irrelevant as long as it doesn't interfere.

You may instead want to convert to the printer/paper space (with the same options you use for printing - for me LOGO Colorful Perceptual mapping with no BPC), editing in this space and printing with No Color Management. All your image colours will, by definition, be something that will print.

I usually find that a modest S-curve on the composite RGB (in Color mode) restores the saturation that I'm after. Also adjustment of the black point (in Luminosity mode) to the point where it starts to clip - most profiles set absolute black too light.

The preceding applies mainly to matte/rag papers which I currently use for 99% of my personal work.

[Henry Ambrose]

You'll want a really fine monitor if you are working in the big color spaces. If you can't display the space on the monitor you will end up guessing about what color you get in your print. Kind of defeats the whole purpose of color management. Although I will say that what Gordon is saying takes some of that into account and seems a rational scheme.

If you send files out for repro to lots of different clients Adobe 98 is what to pick. For photographers who use different printers or different vendors to supply prints Adobe 98 is likely the best answer.

Perhaps if you're printing consistently on machines with huge gamuts a space that matches the capability of your device is more appropriate. But you're still guessing without a monitor that displays the space you've chosen.

[Gordon Moat]

Henry brings up an important point in this, which is emphasizing the monitor. Unfortunately only a handful of recently released monitors approach the limits of AdobeRGB, and many fall short of sRGB. While sRGB and AdobeRGB only differ in the green primaries, that difference is enough to make AdobeRGB a slightly bigger space.

You have to understand that the realm I started in was CMYK editing, because images went to a printing place for output. While in college (1994 through 1998) I rarely had the opportunity to work on a really good monitor (at that time a Radius). So without the benefit of these wonderful monitors available in the last few years, the other choice was to learn to get use to the numbers. I learned that a certain percentage of Magenta and Yellow gave a specific printed result, and sometimes adding a small percentage of Cyan brightened a colour; and many other aspects of printing.

I am somewhat of an advocate in professional circles of pushing learning proper CMYK relationships, which quite often either causes an uproar, or falls on deaf ears. Rather than bitch about this, those who are only comfortable with RGB spaces should probably stick with that working method. Those willing to learn CMYK relationships, or to go further in spot colours, substituting other ink types in four colour runs, touch plates, or several other interesting choices, can have far greater control of their images in printed materials.

If all you do is match your prints to your monitor, you will be giving yourself a limitation. RGB colour spaces clip many CMYK potential outputs. A great deal of commercial printing is moving beyond four colour output, with five and six colour outputs and even substitute inks becoming not much mroe costly than traditional CMYK. Even on-demand printing is moving towards five colour with the Kodak NexPress, and soon to six and seven colour with a newer HP Indigo system soon to be released . . . so why limit yourself to three colours just because that is how your monitor functions.

Ciao!

Gordon Moat
A G Studio