How to Color Correct RGB Images Easily in Photoshop
I’m back again to bring you the next trick in my arsenal of Photoshop goodies. The subject today is color correction. Specifically RGB color correction, for web and screen (monitor, tv, little camera screen, iPhone) use.
There are 2 major, accepted color scales out there for consumption by human eyes – additive color and subtractive color. Subtractive color is accomplished via some sort of dyeing, screening or printing method. This is achieved by mixing either custom ink colors, or adopting a color scale , which in the subtractive realm of color, is called CMYK.
This refers to the 4 base colors used to physically, in paint or dye form, mix together to allow the formation of any color in the Cyan Magenta Yellow Black scale. This is what’s knows as CMYK – but i’m not sure why K stands for black though.
Additive color is the realm of discussion in this article. Additive color refers to the scale of color produced by adding different colors of light (rather than ink) to produce an image or color shade. In additive color, when you add the 3 primary colors together, Red Green and Blue (RGB), you get pure white, as illustrated in the additive color wheel above. Whereas if you mix together Cyan, Magenta, Yellow, and Black inks, you get a dull brown.
Since RGB is the primary color scale for all monitors, phones, screens, laptops, anything that produces light; we will be discussing this today, as a way to empower you to be able to have brilliant images on your websites, and to get the most out of the pictures you snap in with your camera in any condition. We begin with a picture of a clearing on the ocean.
The following picture looks dull, discolored and too red. But you’d be surprised how much color information is contained in the picture, that simply needs to be brought out.
Open the image in Photoshop and you can follow along as you read the article. The tool we will be using can be found in the Image menu under Adjustments, and it’s called Levels. Otherwise it can be Hotkeyed at Ctrl-L.
The levels panel is one of the most used panels in Photoshop. You will also find Auto Levels. It is not recommended to use Auto Levels because it simply cannot replace the eye, and most importantly the taste of the viewer.
Once you have the levels panel open, there is a simple way to tell if all of the available color information is being used. The following is the levels output from the original image of the clearing on the water, showing a red discrepancy where all of the available color frequencies aren’t being utilized to their potential:
In order to correct this, and the inherent lack of color and brightness in the image, we need to give each respective primary color its own attention.
Using the Channel picker at the top we first choose the Red channel. Next, pull the right, white slider over to the left where the dots begin to appear on the graph, indicating the channels are being used. Next pull the left, black slider over to the right to the point where the channel begins to show usage. Do this for red, green, and blue respectively.
As you make these changes, make sure the Preview checkbox is ticked so you can see your changes in action. Here’s what the process looks like, after gradually fixing red, green and blue:
Notice that even when we only fix the red channel, the picture already gets slightly brighter and richer. By bringing these sliders in, we are essentially telling Photoshop to spread the available color information over a wider range of color frequencies, and thus fill out the full spectrum more richly. Next we move on to the green channel.
At this juncture shown above, the picture starts to become richer and more saturated with color.
After finally adjusting the blue channel below, we can see the picture is at a very rich stage. Details that weren’t previously visible shine out now. What used to be shadows in the bushes are now more bushes, more leaves, more detail. And you would have never known the image contains all this information if you didn’t open the Levels panel.
Using these steps, you can take any RGB image and really pull the most out of the information that’s there.
Not all the detail in a picture is immediately visible to the naked eye. But with the Photoshop Levels tool you can maximize on detail and quality for each image.