RGB Adobe 1998 vs. SRGB

<p>I've been shooting RGB Adobe 1998 ever since I got into Digital. Recently, however, I read on a pro lab's website that all printers only read SRGB and files that are sent in should be SRGB if not the lab would convert them to srgb before printing. If this is true, is there any reason to shoot RGB for pictures that are going to be printed?</p>

<p>It is not true.<br>

Check with your lab for your specific situation.</p>

<p>More often than not, you can get an optimized profile from them to use.</p>

<p>Hmm. Do you know which pictures you're going to print before you take them? If so, well I've been at this game a while but I must be missing something because I can't, and like all poor souls with this lack of foresight I have to take photographs offering me the widest possible range of options for colour, applications and processing- and thats Raw. </p>

<p>In any case the person advising you is wrong. Some printers can get outside the sRGB gamut, though apparently not the machines employed by this lab. Using a profile appropriate to the medium (paper) and printing machine will help you optimise colour for an individual image without risking the lab converting your colourspace rather randomly. If the lab doesn't provide profiles, use another. </p>

 

<p>There is no such thing as an sRGB printer (that color space is based on a theoretical CRT display). So no, the labs <strong>demand</strong> sRGB but they have to convert to some other color space to make a print. Unless you are only using this lab, today and in the future, best to use a larger color space, convert to sRGB for this lab and hope for the best. I say this because you have <strong>zero</strong> control for soft proofing or converting the data to this output device. Flying a bit blind. So no, all printers absolutely do not read sRGB, many will not accept an RGB document (the drives demand CMYK!). </p>

<p>For information about RGB color spaces, why you’d want something larger than sRGB, certainly for an archive color space, see:<br>

http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf</p>

<p>David: Yes, I know which ones will be printed. When shooting sports or schools they're all printed.</p>

<p>If you shoot in RAW format, the color space makes no difference. It is applied only when you view, edit or convert the image. If you shoot in TIFF or JPEG format, then you are committed to the selected color space. When editing, Adobe RGB (or better, Profoto RGB) has more tolerance for adjustments. Once adjusted, you can convert the results sRGB for printing without noticeable loss.</p>

<p>Theoretically, a processing lab could "read" any color space and use it accurately. In general, it's safer to convert the images to sRGB before submitting them for printing at a lab. If you adjust the images using a calibrated monitor, it's best to instruct the lab to print them without further adjustments.</p>

<p>You have more options when printing at home. If you print from a color-managed application like Photoshop, the color space doesn't matter - the software does the necessary conversions automatically. If you instruction Photoshop to manage the color when printing, you get the best results using a print profile for that printer and paper combination. If you let the printer manage the color, find a combination of settings that works best for you. Either way, the results will be reasonably consistent from image to image.</p>

<p>If you print from a non-CMS program, like Internet Explorer or Outlook Express, you won't have a choice which color space to use. It may be that sRGB, in combination with printer settings, will work best, or some other color space and settings. That usually requires a lot of trial and error, which takes time and wastes material. If you sent images to unsophisticated recipients, it's usually best to convert them to sRGB. That might include most minilabs.</p>

<blockquote>

<p>If you print from a color-managed application like Photoshop, the color space doesn't matter - the software does the necessary conversions automatically</p>

</blockquote>

<p>Not clear. The encoding color space (the RGB working space) does indeed make a difference in the final output. That is, if you start with sRGB versus ProPhoto RGB as an example, but use the same output profile and settings, there will be a difference in many printers (that exceed sRGB in this example, there are plenty). </p>

<p>Andrew,<br>

Recently I did a test. I edit in PS CS5 using the Prophoto RGB color space and print on an Epson 2200.<br>

First, I loaded an image and printed it using the correct color profile for the paper.<br>

Second, I converted the Prophoto to Adobe RGB and printed it again, making no changes, and on the same sheet of photo paper.<br>

Third, I closed and reopened the same image and then converted it to sRGB, and printed it again. As before, I made no additional changes.<br>

When I examined the images, all three printed very nicely and I could discern NO noticible differences.</p>

<p> I expected to see a difference between the three. Shouldn't I have?</p>

<p>Harold</p>

<p>Harold, much depends on the image gamut itself. Had you provided an image who’s gamut exceeded Adobe RGB (1998), those colors could be output on the 2200 (an older, lower gamut printer by today’s standards) assuming those colors fell within the gamut of this printer. Otherwise I’d expect you’d see no difference. </p>

<blockquote>

<p>When I examined the images, all three printed very nicely and I could discern NO noticeable differences.<br>

I expected to see a difference between the three. Shouldn't I have?</p>

</blockquote>

<p>You are using a profile for the printer, even if you do not realize it. If you don't choose one for the printer, the printer will provide one to the calling software. Even if you select "none" on the printer, it just provides a zero adjusted one. Ether way, the printer gets a profile to print with. Hopefully the one it gets has a wide enough gamut to do the job.</p>

<p>The difference is one is a guess, and one is not. Most of the time a "guess" is an educated one providing all materials are provided by the same manufacturer. People like me, who enjoys the fruits of other worlds, need a broad gamut and a custom profile.</p>

 

<p>On another note, you should *always* use as large of a colour palette as your software allows. Once a colour has been removed, converting to a broader palette will not get it back; it is gone forever.</p>

<p>(Just when I thought I understood this stuff...)<br>

OK. I understand that once lost, color data cannot be recovered. But how about this...<br>

Photo A - taken from Lightroom (which, I believe, operates in ProPhoto RGB) into PS CS5 set to edit in ProPhoto RGB. Then (in PS) convert to sRGB.<br>

Photo B - (same image) taken straight from camera into PS which is configured to edit in sRGB. In other words, it has never been in a color space other than sRGB.<br>

Question: Won't these two images be identical. If the sRGB gamut is only so large, why would an image that was originally in ProPhoto gamut and down-converted to sRGB, the smaller gamut, be any different than the one that had never been in anything else?</p>

<p>Harold</p>

 

<p>Harold, much depends on the image gamut itself. Had you provided an image who’s gamut exceeded Adobe RGB (1998), those colors could be output on the 2200 (an older, lower gamut printer by today’s standards) assuming those colors fell within the gamut of this printer. Otherwise I’d expect you’d see no difference. </p>

<p>Lightroom’s underlying color processing space is very similar to ProPhoto. But you can export in any number of other color spaces so check that. When you tell LR to export to a TIFF (or open in Photoshop), the color space is based on the preferences set. So while the processing might be ProPhoto internally, what comes out the back end, into Photoshop may be much smaller. </p>

<p>It depends on your image.</p>

<p>If I had an image of a white backdrop with a black hammer, my gamut (simply speaking) may only need two colours. Your B would seam unchanged.</p>

<p>If I had sunset, full of the rich colour that something like that contains. The key here would be to look for grads. Its the gradual sweep from one colour/tone to the next that jacks up the gamut. You would see a noticeable difference on the B image.</p>

<p>You need to look at your images in this way. Also noting that your monitor is incapable of reproducing the full range of your image (sRGB, mentioned above). I keep a stock of 4x6 paper around for the "real" proof before I commit big amounts of ink.</p>

<p> </p>

<p>Andrew Rodney said...<br>

<em>Not clear. The encoding color space (the RGB working space) does indeed make a difference in the final output. That is, if you start with sRGB versus ProPhoto RGB as an example, but use the same output profile and settings, there will be a difference in many printers (that exceed sRGB in this example, there are plenty).</em></p>

<p>There are minor differences at the extreme limits of the color gamut which may or may not be visible in some printers or monitors - Prophoto RGB > Adobe RGB > sRGB. What I'm saying here is that Photoshop (or other CMS application) interprets the digital words in the image file according to the embedded color space. There will be little difference in the appearance of these files if you convert from one space to another. However, some information is lost once you convert to a smaller color space, and not restored if you convert back. You can use soft proofing in Photoshop to highlight differences gamut limitations.</p>

<p>You can see how various color spaces behave if you "Apply" different spaces within Photoshop. This process changes the representation of the digital file without changing the actual numbers.</p>

<blockquote>

<p>What I'm saying here is that Photoshop (or other CMS application) interprets the digital words in the image file according to the embedded color space.</p>

</blockquote>

<p>Agreed. But if the encoding is a smaller color space, but the capture and output device have that gamut potential, you are throwing away color that exists and can be reproduced. It is not that the sRGB image looks like crap in comparison. You are wasting gamut from your capture and output device that exists that exceed sRGB. IF saturated colors are important to your imagery, you’ll notice the difference. </p>

<blockquote>

<p>There will be little difference in the appearance of these files if you convert from one space to another.</p>

</blockquote>

<p>On-screen most likely. On a print, not necessarily depending on the output device and the document color space. <br>

There are way, way more colors that can be defined in something like ProPhoto RGB than you could possibly output, true. But we have to live with a disconnect between the simple shapes of RGB working space and the vastly more complex shapes of output color spaces to the point we're trying to fit round pegs in square holes. To do this, you need a much larger square hole. Simple matrix profiles of RGB working spaces when plotted 3 dimensionally illustrate that they reach their maximum saturation at high luminance levels. The opposite is seen with print (output) color spaces. Printers produce color by adding ink or some colorant, working space profiles are based on building more saturation by adding more light due to the differences in subtractive and additive color models. To counter this, you need a really big RGB working space like ProPhoto RGB again due to the simple size and to fit the round peg in the bigger square hole.<br>

Then there is the issue of very dark colors of intense saturation which do occur in nature and we can capture with many devices. Many of these colors fall outside Adobe RGB (1998) and when you encode into such a space, you clip the colors to the degree that smooth gradations become solid blobs in print, again due to the dissimilar shapes and differences in how the two spaces relate to luminance.Printers produce color by adding ink, working space profiles which are theoritically based on emissive devices are based on building more saturation by adding more light. These are due to the differences in subtractive and additive color models. There's the question of clipping. It's not at all hard to capture colors that are outside Adobe RGB. If you convert to this or a smaller space from a capture device that exceeds this gamut, gradations of those colors get clipped to solid blobs in these dark areas of color space. So the advantage of ProPhoto isn't only about retaining all those out-of-gamut colors it's also about maintaining the dissimilarities between them, so that you can map them into a printable color space as gradations rather than ending up as blobs. <br /> </p>

<p>While there are way, way more colors that can be defined in something like ProPhoto RGB than you could possibly print, we have to deal with a significant disconnect between these simple shapes of RGB working space and the vastly more complex shapes of output color spaces. Simple matrix profiles of RGB working spaces when plotted 3 dimensionally illustrate that they reach their maximum saturation at high luminance levels which makes sense since are based on building more saturation by adding more light. The opposite is seen with print (output) color spaces where this is accomplished by adding ink; a subtractive color models. One reason we need such big RGB working space like ProPhoto RGB again due to its simple size and to counter the disconnect between mapping to the output space without potentially clipping. There can be issues where very dark colors of intense saturation which do occur in nature and we can capture with many devices don’t map properly with a smaller working space. Many of these darker colors fall outside Adobe RGB (1998). When you encode into such a space, you clip the colors to the degree that smooth gradations become solid blobs in print, again due to the dissimilar shapes and differences in how the two spaces relate to luminance. I suspect this is why Adobe picked ProPhoto RGB for the processing color space in their raw converters. That again is something one can see on a print, assuming the printer has a sufficient gamut (and many modern ink jets do). </p>

 

<p>The answer depends on printer gamut.<br>

If printer gamut is large, you can stay in larger color space (Adobe 1998 or Prophoto).<br>

If printer gamut is small, it is better to stay in sRGB color space.<br>

Lab printers can have small gamut, so the suggestion to submit images in sRGB.<br>

The conversion from a large color space to a smaller one (may be smaller than sRGB) is problematic.<br>

Compressing a huge lightnes range and, worse, a huge chroma range is not able to produce a pleasant rendition.</p>

<p> </p>

<blockquote>

<p>If printer gamut is small, it is better to stay in sRGB color space.</p>

</blockquote>

<p>Below you can see a slice of several common, smaller gamut, sliver output devices plotted in 3d over sRGB. The solid red plot is sRGB, the colors that exceed that gamut is shown in the colors that would clip<strong> IF using sRGB</strong>. Are any of these colors important to your images? And this is one slice, there are other colors that clip to such devices using sRGB. If you use sRGB, you will not get crap! You will also not use all the color gamut of the printers which seems like a waste to me. <br>

<img src="http://digitaldog.net/files/sRGB_vs_SilverPrinters.jpg" alt="" width="603" height="1749" /></p>

<p>My info are different.<br>

I get profiles from a lab, in italy (they suggest sRGB as color space). I printed using the lab and softproofed my images.<br>

I modified the image using my own software to get better results than using relative or perceptual from their printer profile.<br>

The prints were excellent, but colors are well inside sRGB.<br>

Just a general example of gamut inside sRGB:<br>

<img src="http://img225.imageshack.us/img225/7433/frontierr.jpg" alt="" /></p>

 

<p>Jacopo, the gamut of the printer is shockingly small which makes me suspicious of the profile itself. My custom Frontier profile is significantly larger. <br>

There are a number of ways to pass data through a Frontier. One allows the use of profiles and that’s how mine was built. The others restrict sRGB data and I wonder if this profile was built under that front end. The gamut is super tiny! </p>

<p>I don't know. But I can assure you that the gamut of the lab I used, may be more than one year ago, was tiny too. I used the profile from the lab to get my conclusions. I don't remember the lab printer. But the image was modified based on the profile, so I think it was a good profile.</p>