Preserve the Colors of your Images Recently Ron sent me an email and hinted me towards the fact that I missed the last mile on my workflow tutorials.
I was asked to give some more insight into the process of preparing images for web viewing and/or printing.
In this tutorial I am going to cover some of the basics of color profiling and in the next tutorial I am going to talk a bit about resizing and compression of images. After all you want your images to look good without annoying your viewers (and your wallet) by large data transfers. As you can see this site has a reasonable amount of graphics, but (hopefully) still loads fairly quickly. Part of the reason (besides a good host) is that I optimize my images for online viewing. Since I have automated the process, I forgot to cover this subject. You can use the same technique to send your pictures via email.
Color Profiles and Management
I am by no means an expert in color profiling, nor do I understand all of it. But I can give you some tips on what worked for me without drifting too much into technical jargon.
Color Management should be part of your digital workflow and it is tightly interwoven with all the applications.
Since different devices use different technology (an LCD uses light and color filters to render pixels while an inkjet puts ink onto a paper), you need color management to make the picture look the same on either of them. You want the picture to be printed the same way it looks on your screen. Today's consumer grade LCD screens are often too bright and too cold (blue/green tint). I guess the reason behind this is that manufacturers want them to look brighter in the show room. Unfortunately, this really messes up your color management, so if you are serious about getting the best quality from your pictures, check out my short article on LCD Color Calibration.
Even after you calibrated your monitor, you still need an application like Photoshop that supports color management. As far as I understand the process, the monitor profile consists of two parts. One part is loaded in the operating system (the one that converts a standard color space to the color space of your monitor) and another part is used by the application.
All you need to worry about is that your application supports color management. On some LCDs (like my laptop screen) I can see a visible difference between an image that I open in Photoshop on the calibrated monitor and one I open with the Windows picture viewer.
In order to color proof your image for your printing service, you need an ICC Profile. Since EZPrints offers good prices and a color profile (EZPrints Profile), I am going to use them as an example. Simply download the profile and right click on the file. Select "Install Profile" and start (or restart) Photoshop.
In Photoshop open the picture you wish to color proof.
Go to View -> Proof Setup -> Custom
Under Device to Simulate select ezprints.icc (or whatever printer you want to use) and leave the rendering intent on Relative Colorimetric.
Now you can do two things:
1) You can go to View -> Gamut Warning and let Photoshop highlight the areas in your picture that are out of Gamut (that have levels of saturation your printer cannot reproduce). If you have a lot of those areas and if the color range is wide, you will see posterization effects. That usually happens when you try to boost the saturation too much.
2) Or you can go to View -> Proof Colors. Provided your Monitor is calibrated and able to reproduce the entire color range (that's usually the case, as a monitor has a wider color space than prints), you will be able to preview exactly how the final print colors will look like. Don't even try this with an uncalibrated screen.
I have also set up Photoshop to use ProPhoto RGB as my working color space (Edit -> Color Settings). For some reason, Photoshop only lets you select ProPhoto RGB after clicking the "More Options Tab" (which cost me quite some time to find out).
Ron asked: "The instructors for Photoshop at the UC ext. courses there in Cupertino always said to use Adobe RGB color space. Now I see that people say sRGB might be better."
Color Profiling, Color Space, Color Management: if all of this sounds confusing to you, let me assure you that you are not alone.
For the past years I have been using ProPhoto RGB for editing and sRGB for printing and web publishing with good results. The only reason I can use ProPhoto RGB is the fact that I shoot mostly RAW images and do the conversion myself. When I "develop" the RAW file I can choose whatever color space I wish (RAW files do not contain color, only luminance) and I can use 16-bit color. If you are shooting JPG, you should set your camera to Adobe RGB color space (Most cameras offer sRGB and Adobe RGB).
Although my final goal is to produce a picture in sRGB, my entire workflow is based on ProPhoto RGB since it offers a much larger color space than sRGB does. As my camera does also record more colors than the sRGB color space can reproduce, I know that I will preserve all colors by choosing ProPhoto RGB, which is one of the widest color spaces available. sRGB and even Adobe RGB will not be able to reproduce ALL the colors my camera can record and might end up looking a bit flat.
When you work with ProPhoto RGB (or even with Adobe RGB), you should work with 16-bit files in order to avoid banding effects (since the color space is that much bigger, you need more bits).
In the picture below, I put 3 screenshots next to each other, showing how much highlight clipping one can expect when selecting different color space profiles (the red areas are indications of clipped highlights in Adobe Camera RAW). Those colors might be washed out in the final result.
So obviously ProPhoto RGB gives us a lot less clipping (or a wider gamut range).
That is the reason for me to choose ProPhoto RGB for photo editing.
One has to be careful though, since the color range is so wide, that it is arguable what is still visible. The color space of most monitors is usually close to sRGB and that of most printers is even less (they cannot reproduce those extremely high saturated colors).
Therefore, after I have done all my editing, I convert all my images to sRGB for printing and web viewing.
The reason is that EZPrints and most other printing companies expect images to be uploaded in sRGB and that they have set up their equipment this way. I still color proof everything, but I convert to sRGB before sending it out.
For web viewing you also have to choose sRGB, since web browsers do not make use of color management profiles. And since color information may not be stored in your optimized jpg (see next tutorial), most browsers and operating systems assume sRGB per default.
To convert to sRGB simply go to:
Edit -> Convert to Profile
Conversion Options: Engine: Adobe, Intent: Perceptual, Black Point Compensation, Dither
Since web browsers usually ignore color profiles or have no use for them, most people don't even save them for images to be uploaded online.
What happens if an image is in ProPhoto RGB but the browser assumes it is sRGB, can be seen below (the images will look identical in Photoshop if we tell it that the image on the right is actually in ProPhoto RGB color space).
Depending on your monitor, the results might look more or less dramatic.
Image converted to sRGB and then saved
Image saved in ProPhoto RGB
Basically the Browser simply
remaps misinterprets the colors of the much wider color space. But since the image didn't fill the entire color space, it now looks flat.
So finally we are able to answer Ron's question:
For editing we should use a color space with a wider Gamut range such as ProPhoto RGB or Adobe RGB, but for printing and displaying we should always convert to sRGB (after you have made all your image adjustments). I usually make the conversion to sRGB followed by the conversion to 8-bit the last steps of my image processing actions.
Creating a Profile for your own Printer
Colorvision also offers a product to create a profile for your own printer. I have never done it, since I don't produce my own prints (SmugMug handles that so nicely for me and I can use their profile). I own a Canon printer that produces a reddish hue on my pictures, but it is sufficient for some cards and small prints. If you are planning to produce your own high quality prints, you should probably check out the PrintFIX from Colorvision. It works similar to the Spyder for your prints and lets you create a profile for your printer in order to match up the results to your screen.
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