Visualizing Color Spaces

In Astrophotography, and in photography in general, I display my work in three different media: my monitor, the internet and in print. How an image is presented depends somewhat on calibration and setup of my processing system. Unfortunately, there is not a single way that I can process a single image and display it on all three media in the same way. Some might argue this point and say that properly calibrated equipment will yield WYSIWYG results on a variety of display media but in my experience this cannot be the case. After much trial and error, I have come to the conclusion that I must process final images separately for the different color spaces. This is sure to be a point of controversy but I have tried most every way to use a single image for all three color spaces and it just doesn't' work for me. Although my Canon i9900 and the Chromira printer I use for larger prints come very close to the AdobeRGB 1998 image on my screen, they are still not an exact match. Worse still is sRGB on the web, which make the images look considerably more lifeless and dull.

The hard truth is that different media use different color spaces, each with a different color gamut, and it's just not possible to process an image in one color space and have it look the same in another. Well, you could if you used the least common denominator in terms of color space gamut and displayed and printed them all the same, but this would eliminate the benefits of the other color spaces. Of all the color spaces I normally use, AdobeRGB 1998 has the widest gamut and because of this I use to initially process all my images. Next in the gamut range is sRGB, which is the standard for web display. If you save a file for the web in PhotoShop, it's automatically converted to sRGB, and this is just as well because on the web no one can see all the colors in your beautifully processed image done in the Adobe RGB 1998 color space.

The worst of the lot is some print media using CMYK. RGB and CMYK are completely opposite in how they display colors.

The best way for me to visualize the differences was to try it on my own system. This was very easy to do using a test image I built myself in a couple of minutes. Credit goes to and article in creativepro.com for the idea. The images below are obviously not representative of what I see in my monitor because they are all converted to sRGB.

Here's what I did. Using AdobeRGB 1998 as my color space, I created a new 16-bit RGB file PhotoShop with dimensions that allowed the full frame to be displayed on my monitor.

Once the file was created, I selected the gradient tool and picked the spectrum gradient, as in the image below:

Next I dragged the cursor and created a horizontal gradient like the one below. This gradient contains all the colors in the color space.

The next step was to create the shades from pure black to pure white for the color space model. To do this, I created a new layer and used the gradient tool again ,this time to add a new vertical black and white gradient (first gradient on the gradient palette in the first image above) with black at the top. The layer looks like the one in the image below.

Finally, I changed the blending mode of the new layer to hard light and flattened the image. The resulting image is the full color gamut for my monitor in the AdobeRGB 1998 color space - as shown below. Look closely at the image and you'll notice that my monitor has problems producing a smooth gradient between green and yellow and cyan and blue. This shows as a rather solid line in the color space. I assume different monitors will show different problems, or hopefully none at all.

The last step was to duplicate the image and apply the different color models and see the effects it had on the images. For this example I included a Canon i9900 Photo Paper Pro proof below. The difference is readily apparent on my monitor and there are differences in the sRGB color space as well, especially in the all important darker reds and blues present in nebulae.