RE: [ECI-EN] Re: ECI-RGB / Any advantages?

Hello Olaf, Thank you very much for this post. Exactly what I was looking for. For now, at least, I will continue to use AdobeRGB, but I think that it would be interesting, if there is a good upcoming space as you mention, for it to be communicated to software developers, camera manufacturers, etc. once it is ready. This way it would be much easier for users outside of Germany to implement it. Best regards. Darrian -----Mensaje original----- De: eci-en-admin(a)lists.transmedia.de [mailto:eci-en-admin@lists.transmedia.de] En nombre de Olaf Drümmer Enviado el: miércoles, 10 de diciembre de 2003 11:35 Para: Mailing List [ECI-EN] Asunto: [ECI-EN] Re: ECI-RGB / Any advantages? Hi, I would like to draw attention to some aspects sometimes overlooked with regard to this discussion and also to broaden the perspective a little bit: - focus on what's essential! eciRGB is definitely only one of several reasonable options for a working color space RGB profile; so if your image archive happens to be stored using Adobe RGB or what else, or you are successful and happy using whatever you are using at the moment, there typically is no need to switch to eciRGB just for the sake of it. And: nobody _has to_ use eciRGB (though quite a few successful users are using it). Stating eciRGB is a good option should not at all be understood as stating everything else is rubbish. - what's the original? This is one very essential aspect often forgotten. As I see it, the original is not what's out in the real world and getting photographed, nor is it what even the best camera captures. It is what the photographer or the person doing retouching/color correction etc. of the raw image wants it to be. Thus it becomes an issue not only what colors occur in the real world, but also what colors can be printed. - do we really always know where an image is going to be printed? Please do not forget that images may be reused, the initial use being maybe a display ad for a magazine general, then a similar campaign in newsprint, then some digitally printed direct mailing pieces, then a huge poster at some trade show, and so forth. eciRGB at least for many users in Europe has proven to be a very suitable general purpose working color space. Again: is it the only reasonable one? No. Does it have serious deficiencies that some other profile does not have? Not that I know of. - color science does have a decent understanding of what real world colors are. Some admittedly do not occur that often but they may occur. - Ugra in Switzerland has done a research project for Ifra (I am not sure when the report is going to be available, probably first quarter next year, they presented the preliminary results at the Ifra Color Management Working Group during Ifra Expo October 2004 in Leipzig): Ugra compared quite a few common RGB working color spaces and - using quite an impressive range of metrics - arrived at the conclusion that all in all eciRGB comes in first, with a couple of other profiles coming in next very close. - one reason to not necessarily stay in a scanner profile color space (unless you leave it un(re)touched) is that such profiles are not very linear - thus color corrections, retouching etc. can result in unnecessary loss of detail. - there are always trade-offs in every area of our business: e.g. detail vs. gamut (especially as long as 8 bit data is used). If maximum detail is key and there is no need to be prepared for all possible real world/ pritable colors, some profile other than eciRGB may have advantages. - 8bit Lab does have its limitations: less than a third of the possible Lab value triples exist as real world color, i.e. one is only making sensible use of roughly 5 millions out of 16 millions possible color value triples. This _is_ a threat to keeping as much detail as possible. - Jo is right in still asking for a summary of why eciRGB should be considered and what's relevant to know about it. Here is a summary that I have compiled for upload to the ECI website (going to be available there shortly): What is eciRGB 1.0, and why should I care? ------------------------------------------ eciRGB 1.0 is recommended by the European Color Initiative (ECI) for use as an RGB working color space and for color data exchange for ad agencies, publishers, reproduction and printing houses. There are a couple of aspects that led to the development and release of eciRGB by the ECI in 1999: - Up to Adobe Photoshop 5.5 the default for the working color space was the monitor profile of the computer on which Photoshop was running. This turned out to be a less than perfect approach, as every computer may have a different monitor profile, and a working color space should not depend on what happens to be the monitor profile on a given computer, but should always be the same, at least within any given workflow. - Furthermore a monitor profile typically does not cover certain ranges of colors that can easily be produced on a printing press - the major area of weakness of a monitor compared with a press is in the Cyan color region. - Staying in the scanner profile's color space often makes no sense, as a scanner's color space typically is not very uniform (a characteristic offered for example by the Lab color space) this makes them unsuitable for any corrections or editing. - Lab in principle looked like a good alternative candidate, but hardly any widely used software (until very recently) supported editing and retouching for 16 bit Lab data or import of 16 bit Lab images (and while PostScript/EPS supports up to 12 bit Lab data, in PDF 16 bit image data have only been introduced very recently in version 1.5, earlier versions only accommodating a maximum of 8 bit), and 8 bit Lab data was far too inefficient, as only less than a third of all possible Lab color values actually occur in real world color data: which means that out of the 8 bit only a bit more than 6 bit would actually be used, which simply isn't enough. Even with 16 bit Lab the issue arises that it uses twice the amount of data - while the increase in file size often will be moderate due to compression, the amount of RAM needed definitely doubles. - while there were and still are other reasonable offerings around in terms of RGB working space ICC profiles ECI wanted to see one that ... has a gamut that covers all colors that can be printed on today's printing presses - whether sheet fed or web offset, gravure or newsprint - but not much beyond (in order to not to waste precision for bits that never really get used) ... produces a neutral gray whenever the values for Red, Green and Blue are equal ... approximates uniform distribution of color values, i.e. equal difference between two color values in eciRGB mirrors an perceived equal difference when these colors are seen by the human eye ... is based on a Gamma of 1.8 and a light source of 5000K. This profile was created and extensively tested in 1998/1999 and provided to the public free of charge in 1999. Most ECI members have meanwhile based their internal workflows on eciRGB as the preferred (and often the only) RGB working color space, and have been more than satisfied with the advantages achieved. Is eciRGB the only working color space that makes sense? Definitely no. Other experts and user groups in the industry as well as vendors have been working on this issue and have come up with alternative options that may work as well as eciRGB. If you happen to have been working with let's say Adobe RGB or ColorMatch RGB until now, it would not be a good idea to convert your image database to eciRGB just for the sake of then having eciRGB data. Nevertheless, when you are about to set up a new print oriented workflow, the ECI is confident that there are hardly better options than eciRGB (though possibly quite a few that are comparably good). How does eciRGB compare to sRGB? sRGB has seen excessively wide use, as especially HP and Microsoft were promoting it as the standard RGB profile (in the end often going so far that they - whether directly or indirectly - propose not to use any ICC profiles anymore but instead to simply implicitly store and exchange any RGB data as sRGB. More and more digital cameras, low end inkjet printers and even monitors now simply assume sRGB. While this may look like a smart move, it must not be forgotten, that sRGB as a color space has serious weaknesses - there are a lot of colors today's printing presses as well as other output devices like photo printers, large format printers and many inkjets (not to speak of up to date monitors or digital cameras) can produce that cannot be stored in sRGB. If quality is important, sRGB is not an option. Should I get rid of my scanner profiles right away and use eciRGB instead? No, definitely not. Simply assigning eciRGB instead of the specific profile e.g. for a scanner is one of the worst things you can do. Always use the correct source profile for the data at hand, and then convert from that color space into eciRGB. Note 1: What's a working color space anyway? The short answer is, that such a color space is good for working on an image (or rather any color object), whether color correcting or retouching it or editing it in any other way. A working color space can be made such that it is independent of idiosyncrasies of a specific device (e.g. it can be made uniform to preserve detail equally well in each area of the color space). At the same time it can be made such that it serves a class of color spaces well, e.g. that it comprises all or most of the colors that can be output with all monitor and printing devices that are available today. Note 2: In ISO there is currently work underway - as ISO standard "ISO/CD 22028-2 Photography and graphic technology - Extended colour encodings for digital image storage, manipulation and interchange - Part 2: Reference Output Medium Metric RGB colour image encoding (ROMM RGB)" - to possibly arrive at a working color space that is even better than eciRGB or other widely used working color spaces. Sorry for the lengthy post, folks! Olaf Druemmer Vice chairman of the European Color Initiative _______________________________________________ ECI-EN mailing list ECI-EN(a)lists.transmedia.de http://lists.transmedia.de/mailman/listinfo/eci-en