sRGB versus Adobe RGB

If you’re a pro photographer or photo enthusiast, it’s likely that you’ve come across a debate about sRGB (standard Red Green Blue) versus Adobe RGB. If not, these names represent different colour spaces for RGB images. Digital cameras generally shoot and save in RGB, versus the CMYK (Cyan, Magenta, Yellow and Black) colour space that would be used for typical offset printing. There’s also an extended gamut colour space for offset printing known as CMYKOGV, which adds Orange, Green and Violet to the CMYK space to reach outside of the gamut that can be reached with CMYK alone. There’s no such thing as an RGB offset press. The focus of this article is whether Adobe RGB is preferable over sRGB.

Adobe RGB is a profile developed by Adobe in the very late 1990’s, based on the SMPTE 240m standard. The idea was to include the colour range that then predominately CMYK inkjet printers could reproduce. That colour range could then be displayed accurately on a RGB monitor.

sRGB was developed by HP and Microsoft to profile for various output conditions and released in 1996. sRGB is the default RGB profile for images without an assigned profile.

Despite some significant mis-steps in the creation of the Adobe RGB profile, Adobe included it with Photoshop 5.0. At the time, few to no useful profiles were available, so for Photoshop users, Adobe RGB was, essentially, better than nothing. Because of the development errors, Adobe RGB was not as accurate as sRGB.

Because sRGB became an IEC standard in 1999, all images viewed on the web are sRGB by default. sRGB has a slightly smaller gamut, or the range of colours that it can reproduce) than Adobe RGB. In practice, this difference is too small to make for a deciding factor.

The advantage of the slightly expanded gamut of Adobe RGB is apparent in output on certain types of images BUT the workflow has to take into account that display images on the web will be sRGB. So, it would be necessary to maintain at least two image files for each image, one for the source image in Adobe RGB and a second for web display in sRGB. Using straight Adobe RGB images in a web environment, that is, a web browser, will yield dull and inaccurate colours. Proper conversion of each image is essential.

For the photographer whose images are destined for print, it should be understood that outside output houses may not expect or account for Adobe RGB images in their RIP (Raster Image Processor) workflows. So, the output, assuming the image is being reproduced by inkjet or dye sublimation, will be inaccurate. Also, some output house don’t accept sRGB images at all, which would mean that the photographer dedicated to Adobe RGB would have to add another image to his or her growing library of digital assets – one specifically for output at a given output house. Since time is money, Adobe RGB may be the costlier choice for little, if any, gain.

Modern inkjet and dye sub output devices can reproduce a significant portion of either the sRGB or Adobe RGB spaces, but not the entire space of either as compared to a high-end video monitor. For most purposes, from commerical to fine art output, sRGB is more than sufficient for pleasing and ‘correct’ output and is more likely to be viewable for most of the gamut on a modern monitor or HDMI display, versus Adobe RGB’s 75% reproduction on an sRGB monitor.

So, both colour spaces can yield accurate reproduction but one, sRGB, is practical across more media without jumping through hoops.

Overprint Preview, Layers and Separations in Acrobat Reader, Pro and DC

To view overprints in Acrobat Reader, Pro or DC, open the source document, navigate to the “Preferences” option in the Acrobat menu. In the window that opens, highlight “Page Display” under “Category” in the left-hand pane. In the right-hand part of the window, locate the option “Use Overprint Preview” and select the option to the right from the drop-down choices, “Always”. Here’s a view of that setting:

Acrobat Pro and DC can “toggle” overprint preview, as well as view separations. For professionals in the printing industry that are viewing artwork for mechanical correctness, this is the correct and recommended way to view that artwork since this is how it will be separated to plates and go to press.

Separations are often mistakenly called “layers.” Layers are just that – different levels in a files that may contain different elements, like images, decoration or other features, placed on these different levels for mechanical reasons. Any number of different colours can exist on a single layer, but only one ink (or varnish or emboss or stamp, and so forth) can exist per separation.

To view separations and overprints in Acrobat Pro or DC, navigate to “Tools” and select and click “Print Production”.

In the pane that opens on the right-hand side of the viewport, select “Output Preview”.

In the Output Preview box that opens, note the option near the top of the window called “Simulate Overprinting”. By alternatively ticking and un-ticking this box, the displayed document will alternate between appearing with and without overprint.

Directly to the right of the “Simulate Overprint” option, Acrobat displays whether or nt overprint is present in the document being previewed. Separations can be toggled on and off by selecting the tick mark next to the colour name in the “Separations” pane on the lower half of the Output Preview window.

If there are layers in the file being viewed, those can be viewed by clicking the right-facing arrow on the left-most edge of the displayport. 

Several icons will become visible above the arrow’s location. Click on the icon that looks like layers of sheets of paper.

Whatever layers that are present will appear in the Layers tab that opens. Clicking on the eye icon will turn individual layers on or off.This feature is not meant to check colour separations.

Checking seps should be done ONLY with all layers on, just as the file would be used for production. Otherwise, there is a reasonable chance that an element on a turned-off layer that will interact with the rest of the art in the document when the going to press will not be noticed.

Scanning and Printing Fine Art

Fine artists that sketch, draw, do engraving, silkscreen or paint have a tougher path to replicating their output than digital artists and photographers. Since the material starts in an analogue form, making a reproduction means creating a digital file that can be used to image the reproduction media.

DIY Solutions Suck

Why not just take a photo? The answer is that all except the highest-end professional cameras don’t match the dMax, or maximum density, that contributes to sought-after ‘good blacks’ and excellent contrast and balance in the digital file. Further, optical distortion introduced by the lens optics of the taking camera will change the image somewhat. It’s possible to compensate for this problem with software, but it’s not an ideal solution since the alterations introduced by the software might be a sticking point for archivists and for purists.

One thing to keep in mind is that there is no utterly exact method of reproduction. There will be some variation from the original that will be detectable. Obviously, this is a good thing on some level. Most fine artists don’t intend to become their generation’s Currier and Ives. Still, for fine artists and their fans, reproduction is a way to own an authorised piece of art that would otherwise be inaccessible.

On the other hand, it is possible for the fine artist to begin the creative process with reproduction in mind. Rather than following the digital route, there are many methods of reproduction, like silkscreen, seriagraph, lithograph, engraving and many other systems that allow for direct, analogue creation of multiple pieces of essentially the same work.

If this is not the intent, the question returns to the process of digital reproduction. There are two methods for acquiring digital files for further production from painting, watercolor and other hand works. Very large format flatbed scanning, very much like a giant copier, only with extreme resolution and precise colour, is the more expensive and more precise method, arguably. The use of a large-format camera, 4×5 inch, usually, with an extremely high-resolution digital back in place of film is the other method. I say ‘arguably’ because the differences are so minute as to become the domain of subjective interpretation. It might be advisable for the artist or his agent to discuss the goal of the capture process with the vendor and do some tests to find if one process is preferable.

Here are links to a number of vendors with good reputations in the industry:

The first company in the list uses large-format scanning and the last company uses a camera method. All of these companies print on a variety of material, like canvas, watercolour and bamboo, but the middle company can make matchprints that are laminated to any surface, including metals and wood.

 

So far, there’s no way to exactly reproduce a brushstroke or daub, but that’s a good thing. Right?