Adobe RGB 1998 to CMYK (in less than 1000 years)

[p_low]

Only a photographer will understand how much time I have used to prepare over 100 images for an upcoming

publication and exhibition. In order to keep my options open I have done all the work in the Adobe RGB 1998

colorspace. Now all the 16-bit images look fine enough in this color space on my monitor that I have carefully

calibrated. Also light and dark points are in order. But when I proof the colors with the "color gammut warning"

in Adobe CS3 set to CMYK (US Web Coated SWOP v2) I can see that many colors are outside the gammut of the CMYK

color space.

 

My printer wants the files in CMYK. So I am wondering what to do about this to avoid a disaster?

 

Do I have to make individual adjustments to each of my 100 images using curves or selective color until

everything is within the CMYK color space when I check the color gammut warning? Hopefully not as I am afraid

this may take till eternity and I have a deadline.

 

Can I just convert my images from Adobe RGB 1998 to a more CMYK-friendly color space before doing the CMYK

conversion... (what color spacer could that be??)

 

 

or..... if I am lucky you have a better suggestion.

 

Thanks

[AaronFalkenberg]

Do not just convert to Adobe's generic CMYK profile. Also, the gamut warning is really strict; hues that are just a fraction out of gamut will be totally greyed. It looks scary and will make you think it will print horribly. In some cases it might, in others it will not.

The most important thing to do is to try to get the actual profile your printer uses, and if possible, run a test print. It might be that very little adjustment is need, it is impossible to know without actually seeing a test print on the equipment.

[patricklavoie]

My printer wants the files in CMYK. So I am wondering what to do about this to avoid a disaster?.."

 

let a expert do it, like him or a graphic designer that know is stuff

 

Do I have to make individual adjustments to each of my 100 images using curves or selective color until everything is within the CMYK color space when I check the color gammut warning?.."

 

Yep, and using a custom ICC profile given by the print shop will also help.

 

Can I just convert my images from Adobe RGB 1998 to a more CMYK-friendly color space before doing the CMYK conversion... (what color spacer could that be??) .."

 

Yep, convert to profile sRGB, then you need to optimized those file individualy making sure all will print well. Then you transform to CMYK using the appropriate custom profile, then you optimized them to suite your need knowing where you print, on what, glossy or not, magazine or art book etc...

 

My explanation lost you already? refer to point #01 : )

[paul_mounsey]

Hi

I photograph paintings for art gallery catalogues which involves sending the images to the printer as CMYK files. I start in Adobe RGB

do all the adjustments then preview in the printer's recommended profile. I have one copy of the image in Adobe RGB and another in the

CMYK profile preview, I then just compare them. When happy I convert them. Make sure the printer provides you with a fully calibrated

proof and if the job is very important keep asking for proofs until it's right. As a final safety check you can ask to see a wet proof, the

stage before it goes to print.

I'm certainly no pre-press expert but if you ask for a proof you can catch any horrible mistakes. I used to worry myself sick about trying

to achieve certain colours when converting from rgb to cmyk until I learnt some colours just do not want to be photographed or printed!

Ask the printers for any help, they're the best people to ask.

Good luck

Paul

[tony_wellington]

I agree with Paul above. I've printed two books of photography. They have been stand-alone books, not associated with exhibitions.

 

I certainly wouldn't let the printer or anyone else do the conversion. I do my tuning in RGB in CS3 to get it looking how I want the image

to look. Then I use CS3 to convert the image to CMYK. Like Paul, I have both versions open on the screen side by side. I make some

adjustments to the CMYK to try and bring it into line with the RGB. The important thing to note here is that THEY WILL NEVER MATCH

EXACTLY. The two systems use different pigments. For example, you will never get the nice super-rich grassy greens in CMYK that

you can get with RGB. There will also be shifts in other colours. That's the nature of the beast. Red-green-blue are different basic

colours to cyan-magenta-yellow-black, and in combination produce slightly different results.

 

I have never worried too much about the colour gamut warning. It's never proven to help. Just accept that there will be some changes

between RGB and CMYK (which you can lessen by comparing them on your screen). There will also be some changes when you go

from your screen to lithographic printing. Each printer's own inks will even vary slightly depending on where they source them. Are you

printing on a 4 colour or 5, 6, colour machine? Try not to print on anything less than a 4 colour. You don't want your sheets running

through machines more than once.

 

The paper you choose to print on will have an even more dramatic impact on the inks. Have you chosen a paper and seen something

printed on it? In many ways choice of paper is more critical than anything else you do. Also decide whether you want the paper coated

with a machine varnish (this prevents rub-off where printing rubs up against the opposite page). Varnish will also affect the final look

(making it slightly richer but also slightly darker).

 

I also agree with Paul that it's often wise to get a wet proof. But this can be very expensive, particularly for a whole book. So you might

want to get just a basic proof (probably digital) to check layout, and choose some specific pages for wet proofing so you can see what

the printer comes up with.

 

Finally, ask to do a press check. This means you are able to be there when the printing happens to see the test sheets just before they

run the final print. You can then ask for changes if necessary. Mind you, those changes will remain simply increasing or decreasing

individual inks, or the same with the whole lot (ie increasing/decreasing total saturation). And you're limited by the way the images are

laid out on the page as to what alterations you can make. (If you have two images running across the sheet, changing one will affect the

other.) Even at the press check you still won't be able to make the CMYK look like RGB.

 

I live in Australia, and I've just been to China to do a press check on my latest book. For peace of mind, it's essential. But remember

that an off-set printing process will not match what you get from a high quality photo print.

[p_low]

I guess there is also a big difference between working with a local printer versus exploring offshore options. I can follow Tony’s suggestion: i.e. “I certainly wouldn't let the printer or anyone else do the conversion” as I plan to use a similar approach working for the first time with a printer in Thailand. My previous experience is that most printers are very knowledgeable but not always very patient and seldom have much time to spend more than a moment on any looking at any single image. So my plan is to consult with and get a profile from the printer but to do the conversion myself following your tips that for my own convenience I have listed below, then sit beside the printer to revise each file.

 

1) Do not just convert to Adobe's generic CMYK profile

2) Get the actual profile the printer uses.

3) Preview in the printer's recommended profile in CS3 with one copy of the image in Adobe RGB and another in the CMYK profile preview

4) Adjust each file individually (Oh boy!) until it looks right in the CMYK preview (without worrying too much about the color gamut warning?)

5) Make sure the printer provides a fully calibrated proof

6) Keep asking for proofs until it's right.

7) Keep in mind some colours just do not want to be photographed or printed!

 

Patrick, I am curious about your suggestion to “convert to sRGB then optimize those file individually before converting to CMYK. My (very limited) understanding is that sRGB was designed for web images. So I am uncertain about how this could help? ”. Is it because sRGB has such a narrow gamut that it is likely to eliminate most uncertainties?

 

I have chosen a medium weight semi-matt paper that I expect will not have to great an effect on the contrast, shadows and highlights.

 

To complicate matters further I am working on a PC - Don't ask me why! - but the printer is working on a Mac. Is the difference in gamma of these two OS likely to cause a problem?

 

Thanks very much for the useful input.

 

Peter

[patricklavoie]

converting your image to sRGB first will already lower your color gammut, giving you a closer CMYK conversion, so you might already see the problem in that color space. A lot of graphic designer i know (some photographer also) like to work only in that space when they know that all there work will be printed in magazine or else that come from a commercial press. They have less surprise when the CMYK is done. So no, sRGB is not only for the internet.

 

I find the suggestion of getting match print until the color look right kind of stupid (no offense) becasue do you know how much it cost per print? depending of the size and *real* quality final proof, close to 75$/sheet..do you really want to have your 100 picture to have 3-4-5 match each? What i suggest is to leave this job to a pro, giving him direction and approved everything first on a calibrated monitor with a press pdf. then in need have some adjutsment made, then order a set of final proof. You should be pretty close with this set to what you like.

 

After if you can ask to be present for the press approval, meaning you will be beside the guy who print to approved the real print as they are made, review them, corrected them, signed them and go back to your place with a signed copy in hand (one stay with them also); thats your inssurance policy about quality control.

 

Working on a Pc or Mac will have no impact on file quality, gamma or else; if both have a calibrated workflow, it doestn mater on what platform you work.

[p_low]

Thanks Patrick.

 

Less surprise sounds like a good idea, which is why I had thought about converting to a narrower color space before doing CMYK conversion. Recently I had the bad experience of supplying a Tiff-file to a magazine in Adobe RGB that came out terrible in print with grey shadows and technicolor highlights, so I am "sensitized" to this problem - and that was for a magazine produced by a journalist association in Europe. So am not always confident to leave everything up to the "pros" unless I know who I am dealing with beforehand which is not always possible. If I do convert to sRGB will I not lose some nuances of color that otherwise I would be able to retain through the more "risky" process of going direct from Adobe RGB to CMYK? What about Colormatch RGB as an alternative route to sRGB? It is a relief to hear your opinion that working on a PC won't screw up the whole process so thanks for taking the trouble to answer that question too.

[patricklavoie]

P, i heard about ColorMatch color space, but frankly i never use it nor i can explain to you what it is. Never heard people working with it neither, but it must have a reason to exist. Andrew Rodney could eventually pop in and explain it to us.

 

Sure going from Adobe RGB > sRGB will screw up some color, but those color would have been possibly more screw up and similarly screw up if you go directly to CMYK. You are just keeping a device independant file that you can still apply in need a CMYK profile. I always send me image now as sRGB to magazine, news paper and else so they cant screw up too much my image, and since a long time, all is fine.

[tony_wellington]

I'm curious that so many folk suggest that one "gets the actual printer profile". If you are working on an off-set (lithographic) printing

machine, this is surely nonsense. It's not like sending information to a digital printer. The images are converted into 4 colours to make up

plates (either metal or plastic). The plates for each colour are fitted to the drums on the lithographic printer and off you go. If the plates are

wrong, the results are wrong. But lithographic printers don't have actual profiles, as far as I can ascertain. The computers that design the

plates no doubt do, but not the printing machines.

[sean_murphy4]

Actually it is not nonsense. All printers lay down layers of CMYK ink as the paper travels through them, just at different

speeds, precision, and levels of control. A printing press, especially running with CTP (computer-to-plate, direct laser

imaged printing plates) can be run on a repeatable basis regarding density, tone reproduction, and gray balance. Any

device that can repeatedly output color can be profiled for a color managed workflow. A press could run to any arbitrary

combination on these variables, and be profiled if repeatable. Then a printer can provide a profile of their local process,

but few can or do this. Better though is when standardized density, tone reproduction, and gray balance values are used,

implemetations of ISO12647, such as Gracol, Fogra etc. The printer adheres to these standards on a repeatable basis,

conforming to profiles of these standard print conditions on different stocks on differerent presses sheetfed, web etc.

The profiles available from these organizations (Gracol, Fogra, ECI) cover a wide range of print conditions, and each

represents a press running to a known repeatable target state. This way the printer focuses on process control, (which

they are good at) not on color science of profile creation (which they are not always good at).

 

Whether on a PC or a Mac calibrate your montitor to 6500K Gamma 2.2. (Years back Mac systems defaulted arbitraily

to 1.8, but anyone doing modern pre-press should be using 2.2). You indicated that your images are 16 bit, so I surmise

that you have converted from RAW into Adobe RGB. This is a fine working space for many uses. I would even argue

that if even if your camera shot JPEG tagged in sRGB, a one time conversion to AdobeRGB is warranted. Under no

circumstances I would reccomend an AdobeRGB to sRGB conversion, then to CMYK. The fewer conversions the better.

Gamut mapping to the CMYK space is done at output conversion time. Use a profile most like the process your printer

will use, or obtain and use the one they recommend. You said you had US SWOP selected, is that how your book will be

printed? Web press, US standards?

 

Set your CMYK space in PhotoShop to the correct profile. For the most accurate reproduction of color in gamut, use

Absolute Colormetric for your rendering intent, the closest match to the out of gamut color will be used. If your images

are very saturated in the 3/4 tone and shadows, a Perceptual render intent can look better. You can preview the

difference using the Convert to profile dialog. Perceptual is usually a safe choice for images, even though it will remap in

gamut colors as well as out of gamut to keep an image "looking right".

 

I agree that the gamut waring can be of limited use, instead, while in RGB use the Proof Colors option in the View menu.

If you have caibrated your monitor well and have an accurate CMYK profile Photoshop will show you what your image

will print like in CMYK. Use the adustment tools in RGB space, (you have more flexability and more plugins work in RGB

space) to see if you can get the image closer to what you want. Not knowing how the printer you have selected works,

with that caveat, they should be able to provide you with a resonable priced, accurate high end inkjet proof of how your

book will print. Choose a cross section of images to gang together to cross check your book. At set of proofs is always

cheaper than a ruined print job.

 

 

Sean Murphy

Director of Technology

Fusion Systems International

[tony_wellington]

Yes, I agree Sean, that there is a sort of printer "profile" for every off-set printing machine, in theory. But as you also

point out "few can or do this". So, in my experience, a discussion with a printer about profiling for their off-set machine

results in a blank look. Lithographic printers traditionally rely on their eyes and test sheets, making comparisons with

standard charts. Like you say, they don't tend to rely on the "color science of profile creation". We're talking about

technology developed long before computers intersecting with new-fangled computer technology. In the end it's often

something of a leap of faith to go from a computer to an off-set printer. One is very much reliant upon the eyes of the

printer operator. Thus getting proofs and being present for a press check are the best option. My experience suggests

that an inkjet proof is not as accurate as a wet proof for checking colours, but very useful for checking overall layout etc.

 

All your information is excellent, Sean. Hats off to you for taking the time.

[sean_murphy4]

Thanks Tony! I work with photographers, artist and printers, on a regular basis at work, and am somewhat of a color

wonk and standards evangelist. I've been working the proof/press match problem for years with ink jet tech, and in the

last year have found that better control of the press is a key issue. The change to CTP has given control to the printer

that was not possible before. This is what allows us to turn on its head, the concept of profiling the press for color

management and proofing, and instead running the press to a standard, that is described in a profile. Its also what drives

the need for a digtal proof, (usually inkjet, as there is no film for a proof now); or the expense of a press check. When a

proofer and a press are aligned to the same standard, its amazing how well they match. I've worked with printers where

product match color is achieved by running to a color standard, and the operator had no proof!

 

You're absolutly correct about the need for change in the pressroom, as printing to color and grey balance is a big

change for some. Printing to standardized conditions takes a commitmnent to process control, that has to be shared.

 

I realize in my post that the real question posed by P Low which is is there a better profile to use, so if assuming for a

photo book that a sheetfed press is used, either the US Sheetfed profile that ships with PhotoShop, or the GRACoL2006_Coated1v2.icc

proflie available for free from www.gracol.com would work better than US SWOP.

 

Sean Murphy

Director of Technology

Fusion Systems International

[p_low]

Thanks for this input Sean. It is not only theoretically sound but also actually useful, which is a rare combo, so very much appreciated. I would have replied earlier but we have just had a big tropical storm that is now over.

 

It is clear to me now that there are different ways to do the conversion from RGB to CMYK depending on the result I want and the time I have available. I can understand from Patrick’s comments that converting to sRGB is a strategy widely used by commercial photographers who don’t have a lot of time to muck around and need to be sure that their shadows and reds won’t come out like leopard’s spots – but by doing some of the nuances of the image are lost, which could be a problem for art photographers or reproducing paintings as Paul is doing.

 

I am somewhere in the middle.

 

So far I have scanned my 4x5 color negs to 16-bit Tiffs on my Imacon flextight scanner and imported them into Photoshop to adjust all the images in the Adobe RGB color space. Fortunately the printer can provide me with a profile that I assume is calibrated with his monitor but more importantly designed to match the color output on his particular printing press. But I have decided to do as much preparation as possible myself so will attempt the CMYK conversion then review what I have done together with the printer and we will check a few proofs before the press rolls. So my only problem is to figure out the best way to do the conversion from my Adobe RGB colorspace to his CMYK profile and now thanks to the input I have received from you and others I have some ideas about how to do that - and should be finished before the next Olympics.

 

Any hints about what to look out for (apart from leopards and landslides) as I attempt this would be much appreciated. Is it true that reds, blues and greens are the colors that I need to watch most carefully or do the highlights and shadows also tend to bounce about?

[patricklavoie]

P, i dont think you get my concept, so i would give it another shot : )

 

*ATTENTION*

to all color specialist in PN, what im about to say its a simple version of the complicated and huge color management world..dont be upset, its for people who want to know quickly withotu having to read a 500pgs manual.

 

Ok P, follow me.

 

sRGB is not only for commercial photographer that dont want to be stuck at there office for zillion of years or dont want to muck around. For me all photographer are equal when talking color because from the basics, they all want the same thing; a good looking image printed or not that is similar to what they have shot. painting, clothes, fashion, skin tone..they all want the best printed image as possible.

 

What you have to understand is that sRGB is the closest color space you have for your CMYK coversion withotu loosing any more color nuance since sRGB have kind of the same color vs CMYK.

 

Of course you will get some color knock off and will loose some shade and gradation in sRGB, probably the same that you will loose if you go to CMYK, but the thing is that with CMYK you are device DEPENDANTm with a sRGB you are device INDEPENDANT,,whe all like to be independant : )

 

A sRGB file will look good on any medium according that the medium is color calibrated to a minimum, for example, on a calibrated monitor. sRGB will look good on monitor, powerpoint, internet, inkjet and lab all over the world, its the basic all you can eat color space. Since its a small color space that is the closest to CMYK, is then a good thing to be in that color space at one point for many reason. I dont mean to work in it (many people do) as i prefer to work on a larger one to get and maintain all the subtle nuance of every possible color i migth have capture.

 

When using a sRGB as you final (or almost final) destination on a save as copy image, you then assure yourself of good color rendition anywhere or close enought. Since you can see what color will clip, what will append to your shadow, highlight and else tyou can than in need correct any problem at that stage to a certain extend.

 

To be honest with you, i work all my file in a AdobeRGB mode, and when i convert them theres not much degradation from it this conversion, if you have work on a calibrated monitor and dont use the hue saturation tool to get funky over saturated color, the move could be subtle.

 

Blue, orange, brown are the color mostly to be affected when convert, or the one that should give you the most problem when printing in CMYK.

 

Theres many option offer to you, i will quickly explain 2 of them;

 

OPTION 01

work in adobe rgb (or in another color space if you want like pro photo * the conversion will then be more agressive be advice) for as long as you can.

 

convert to profile to sRGB and save as a copy, so you still have your original untouched.

 

from there you can send those file to anywhere withotu too much fear of bad rendition.

 

Since that you now have a universal color space image, you can then transform it to any CMYK flavor, and no more aggresive conversion should append. Of course it depend of where you print, matte paper, glossy paper, type of paper, etc...but if the operator is good and the place you print is good, the color should be pretty close to your sRGB file, that are pretty close to your adobe RGB file visualy. For sure you will have a difference between rgb vs cmyk, but that is the technique i use when in doubt.

 

OPTION 02

ask for the icc profile of your printer, and use convert to profile, locate is profile and applied it..you probably will be scare of the result depending of your original look, but that is the reality. Also, no one only convert and move along (i mean lazy people do) after you should optimized your conversion with curve and other tool to get the most out of it..and this is where normal untrain people get f***. If you apply to much saturation, contrast and else, you risk that this file will have block shadow or other problem.

 

So in the end, i suggest you go as far as your knowledge can bring you, and let someone else take the rest to the best of is knowledge. Dont thrust any oen else except you? fine, so go back to scool, study how to become a graphic designer / commercial printer, and in 3years you will master everything you can to get better result.

 

Then the guy from the commercial press that morning will dont feel to good, and print your file with the wrong setting, or add too much ink for your paper dot gain capacity and all your shadow will be block..or the magazine where you send your file as per there request will use the cheapeast printer in town that use a 2 color press to run a 4 color job....

 

As you see you can only bring the file as far as you can, when you give this file to someone else youre at is mercy.

 

Using both option should give you IF well printed form there side, a pretty good result.

 

I hope i explain myself a bit better this time so you dont think that sRGB is only "..a strategy widely used by commercial photographers who don’t have a lot of time to muck around and need to be sure that their shadows and reds won’t come out like leopard’s spots – but by doing some of the nuances of the image are lost, which could be a problem for art photographers or reproducing paintings.." if the nuance are lost in sRGB, they will be the same in CMYK ; )

 

 

[p_low]

Patrick, I follow your logic that conversion from sRGB to CMYK (or to any other color space) is not as "agressive" in terms of warping the gamut as converting direct from Adobe RGB to CMYK that probably requires more. But what about the conversion from Adobe RGB to sRGB? Isn't that also an "agressive" warp? And even if not isn't two small twists (adobe rgb to srgb to CMYK) the same or even more of a wobbly stretch (counting the detours) than one big leap from adobe rgb direct to CMYK? I guess "seeing is believing" (or close enough) and there is no harm in taking a little time to try both routes with the copies of the same file and see what happens. So I will try that.

 

As for the difference and/or similarities between commercial photography and art photography that is a different discussion, isn't it? Just like the one about film versus digital etc etc. I am not sure whether to agree with you or not. I guess it depends on what you mean by "the best printed image". One of the reasons that I like scanning my negs and runnning them through Photoshop is that if I want I can get results that are NOT similar to what I have shot. But this depends a lot on which day of the week it is.

[patricklavoie]

any conversion could be or not agressive it depend of the starting point. For example a Pro Photo color space

with vivid color will look dull in any other color space. The point is, if you can you could do a sRGB conversion

and have a copy taht could be good looking anywhere, and in need, let say for example when you show this image in

sRGB to a client, when i will see the final CMYK he should not be desapointed too much, comapre to a flashy Pro

Photo image on screen.

 

Like i said, both road will give you lees popy color, and both will get rid of some important data. The thing is

with the CMYK is it will only look good on that particular press and paper, if you have to send somewhere else,

you will have to start from the original again and send this new CMYK file..when you could have just sent the

sRGB already fixed, or convert a new cmyk from this srgb already ready for that purpose. : )

 

I didtn want to comapre any photographic style in my example, i jst want to say that srgb is not only for

commercial photographer as per your statement, any style could use it, and any style want in the end a print that

look like what they think it should look for them. If you like your apple to be purple for a project its fine,

but if you decide to print it you certainly want this apple to be as closely purple as possible of what you think

it was or should be.

 

A best printed image is a best printed image. Theres no best version one and another flavor of best, liek a glod

medal..theres no other gold medal in the olympic, less yellow or more yellow : ) a best print is whatever you

approved to be the best you like for your need and project. not a best approved print across the world, but for you.

 

Its fine to want not similar color , when you decide not to have one. but when you decide to get that purple, its

good to have it.

 

 

Pro Photo is good

 

Adobe RGB is good

 

sRGB is good

 

CMYK is good

 

all depend of your final destination, all depend of where you will see the file, and where you will print it or

display it.

[tony_wellington]

Getting back to P's question about what to look out for in the conversion from RGB to CMYK... I shoot and print a lot of

landscape images. When converting from RGB to CMYK my one big bugbear is not the oranges, browns etc as others

suggest, but rather in the greens. Where I live it is high rainfall, pasture and rainforest, and often livid green. I find it almost

impossible to replicate the rich grassy green I can get in RGB when I convert to CMYK. In the end I have to settle for a

duller green in my books. Of course other colours shift a bit also, but the green issue is the one that drives me nutso. Don't

know if that helps you P?

[sean_murphy4]

One way when printing color on a press that wil help with getting a bit more gamut, as well as detail, would be to check if

your printer can print with stochasitc screens, ie not ruled halftone dots, of 150th or 200th of an inch but small spots of

10 15, 20 microns. This style of printing is more photographic, and can expand the gamut of a given ink/paper

combination. The increase in detail is superb. I can go into more detail for those that are interested.

 

 

 

One of the the things that I've noticed in this discussion is that color space and gamut are used interchangeably. While

they both refer to "the range of colors of a device" they are are not in terms of color management workflow. A color

management system -CMS- uses a device independent color -DIC- space to translate colors into and out of the DIC.

 

All color management systems are based on fundamental work done in the 1930s, (updated in the 1970s) on mapping

human vision mathematically. This created the CIE XYZ colorspace, a tristimulus color space derived directly from

human vision. A tristimulus color system unambiguously defines a color regardless of lighting. Its a huge space, bigger

than all the device gamuts mentioned here (AdobeRGB, sRGB, etc) and its nonlinear, because our eyes aren't. All other

color spaces are derived mathematically from it such as Lab and CIE L*a*b*.

 

Ideally you'd have a program like PhotoShop use CIE XYZ internally and convert colors in and out of it using a profile

that described the colors of the device used, and all colors would be translated correctly, as all device gamuts (camera

printer) would fit within it. Being nonlinear, the XYZ space has historically been computationally expensive to compute in,

to translate device colors like a camera or printer, in to it and out.

 

In 1976 the CIE XYZ system was reworked to be proportional, to make the math of conversion easier, and CIE L*a*b*

was created, a color space that holds all the color we can see and then some. The steps from light to dark are

proportional, from 0 Black to 100 white, 50 is gray. If you graph L*a*b* in 3 dimensions its a flat square block white on

its top center and black on its bottom center. Red Green Blue smeared around the sides. All of the gamuts mentioned fit

inside it. It was still computationally expensive to use to translate the RGB of a scanner or camera into it and get

accurate CMYK for a specific printer out of it. I worked with systems in the 93-95 time frame that used special

accelerator boards in desktop computers to do these transforms.

 

Because of this (and other factors) Adobe created the idea of a working space, and the AdobeRGB space was created to

support it. The idea being to create a smaller space in RGB that could still contain CMYK printers and RGB monitors.

The sRGB space is an ISO take (driven by HP and Microsoft) on Adobe's proprietary but open spec for handling color.

They share many qualities, but were created for different goals. AdobeRGB for digital to print applications -RGB to

CMYK, where sRGB is a standard color space that every one would use for their device, so profiles would not be

needed.

 

From the spec for Adobe1998:

 

The Adobe RGB (1998) color image encoding has a color gamut that is larger than

sRGB (IEC 61966–2.1) and encompasses typical press gamuts. The Adobe RGB (1998) color image

encoding is designed to be suited for display and print production with a broad range of colors.

 

 

From the sRGB spec:

 

Currently, the ICC has one means of tracking and ensuring that a color is correctly mapped from the input to the output

color space. This is done by attaching a profile for the input color space to the image in question. This is appropriate for

high end users. However, there are a broad range of users that do not require this level of flexibility and control.

Additionally, most existing file formats do not, and may never support color profile embedding, and finally, there are a

broad range of uses actually discourage people from appending any extra data to their files. A common standard RGB

color space addresses these issues and is useful and necessary.

We expect application developers and users that do not want the overhead of embedding profiles with documents or

images to convert them to a common color space and store them in that format. Currently there is a plethora of RGB

monitor color spaces attempting to fill this void with little guidance or attempts at standards. There is a need to merge

the many standard and non-standard RGB monitor spaces into a single standard RGB color space.

 

Pardon all the background here, but just as we had to learn about emulsions, contrast grades, toners, etc, we now can

use a little color theory about the tools we use. If you shoot JPEG and your camera supports it set it to AdobeRGB. If

you shoot raw convert to Adobe RGB. You get to the principle Patrick was getting at; your RGB values will match up

well with CMYK printing.

 

Set PhotoShop's working RGB space to AdobeRGB, now no conversions are needed to work in PS. Calibrate your

monitor to 2.2 gamma and make an ICC profile of it and store it in the computers default location for profiles. PhotoShop will

convert AdobeRGB of your file to your monitor RGB on the fly.

 

View your calibrated monitor in about 32-64 lux; that is about as bright as a single D50 fluorescent tube at 8-12 feet

away. (Remember there used to be rules for safelights and enlarger bulbs.) If you're really serious get and EIZO monitor,

it can show 98% of AdobeRGB, and is gray balanced, so you see all the colors in your file with no gamut compression.

 

Set your working CMYK to US sheet-fed -that comes with PS, are better yet, get the Gracol profile from gracol.com

(outstanding grey balance) and use that. A good sheet-fed printer shot be able to give you a proof of your files without a

problem and print them well on a #1, #2 stock.

 

Sean Murphy Director of Technology

Fusion Systems International