My Picture Didn’t Look Like That On My Monitor!

Pt. 1

By Mark

It is time for us to take a little detour on our way to the Grand Canyon, and talk a little bit about color management. We often hear the sentiment expressed by the blog title when people get their photos back or try to display them on a different device than the one they worked on at home. Color Management covers a great deal of territory, so this blog will just cover some critical details.  There are volumes and tomes about the intricacies of this subject and they can make your head spin.  All of us want our images to look the way we envision them no matter the format or medium. 

One of hardest issues to wrestle with is the fact that none of us truly know how something looks to any other person on the planet.  There are people who suffer from color blindness and others whose astigmatism changes their perception of pure black into shades of gray—not 50 perhaps, but who knows?  Those factors are out of our control; but trust me, there are lots of knobs and sliders for us to work with.  We have to establish a common language to describe colors.

There are mathematical models which can tell you what wavelength the color red is—700-635 nanometers, but that doesn’t really help in fixing an image.  The human eye operates between ~400 and 700 nm but, unfortunately, our electronic devices such as printers and monitors can’t accurately reproduce all of the potential color combinations. A key term we need to know is GAMUT.  It is the specific subset of colors which can be displayed. 

Full Gamut of Visible Colors

Full Gamut of Visible Colors

The next key concept we need to know is COLOR SPACE.  A color space is a common set of standards that define a specific Gamut and which can describe a particular color.  In photography, we commonly use three of these: CMYK, L.A.B., and RGB.

CMYK is the most common for professional printing jobs.  Cyan, Magenta, Yellow and Black are combined to create rich deep colors. 

CMYK space.png

L.A.B. takes a completely different approach. As shown in the picture, you have an a channel which starts at green and goes towards the magenta. The b channel goes from blue to yellow.  A separate Lightness channel describes how far out from the black center a specific color sits.  L.A.B. can be very powerful in color correction, but is not the focus of this blog.

L.A.B. Space

L.A.B. Space

We normally work in the RGB color space.  Red, Green and Blue colors are mixed together to form all of the remaining colors. 

RGB

RGB

Unfortunately, RGB does not cover all of the colors that we can see.  There are two common RGB formats we need to understand: Adobe RGB 1998 and sRGB.  sRGB is actually the format used by most electronics. It covers about 35% of visible color.   Adobe RGB covers about 50% and more closely maps to the color range available in CMYK printers.  

RGB versus visible colors

RGB versus visible colors

Amazingly, at best, we are currently able to reproduce only half of the colors our eyes and brains can see.  As technology increases, other formats such as Pro Photo RGB are gaining ground. 

Whew, that is a lot of stuff to take in and we have not even started talking about how we can manage our work.  I guess that will have to wait until next week. 

Let’s Hear It for the Red, Green, and Blue

Most of us know that photos are made up of red, green and blue pixels that our eyes and brain process into the full range of colors we “see”.  The great pointillist painter George Seurat broke his images down into individual dots of color.  If you stand up close they are a mess, but stand back and the dots are transformed into a day in the park.

Photoshop works much the same way.  We spent the last few weeks talking about layers and how they interact, but we need to dig a bit deeper.  Down by the layers tab, is another tab called Channels.  If you select it, you will see four different versions of your picture.  An RGB composite and three greyscales called Red, Green, and Blue.  By default, Photoshop displays them this way because it really contains more info.  If you want to see what they really look like, just go to your Preferences, Ctrl-k or CMD-k on a Mac, => go to interface and check the show channels in color.   If you select them one at a time, you will see the color information for your image. 

If you click on two at a time, you will see how the colors interact to create new colors. 

I don’t recommend you leave them this way, because when we start to work with them later, this view is harder to use.  The grey-scales contain all the info you will need to manipulate the individual channels.  Take a few different kinds of images and look at their channel info.  See how much info you get from the red channel in pictures of people, the green channel in nature images and the blue channel where the sky or sea are dominant.