Photoshop Colour Information
As users push their skills levels from beginner through intermediate to advanced, they also tend to shift the adjustments they use on their images. Beginners start with adjustments that are easy to understand and use, but that may be limited in functionality. As users become more proficient, they’re more willing to give up some ease of use to gain versatility.
The Photo Filter adjustment (Image>Adjustments>Photo Filter) is the simplest of the Warm/Cool category. It allows you to shift the overall look of your image toward any one colour. What’s not immediately apparent is that it can push an image away from any colour by shifting the image toward the opposite colour. For instance, if you find that an image is too orange/yellow, then you’d have to shift the image toward blue/cyan to make it look more neutral (because that’s the colour that appears directly opposite from orange/yellow on the colour wheel). Halfway between looking to orange/yellow and looking to blue/cyan is where the image doesn’t have a colour bias.
The other warm/cool adjustments are more powerful than Photo Filter because they are able to isolate areas of your image based on brightness or colour. The only problem is that along with additional control come the requirements that you think about your image as Photoshop does. That means you’ll have to describe the colour areas, toward which you want to shift, as a combination of red, green and blue or cyan, magenta, yellow and black.
Variations (a visual version of Colour Balance) will allow you to limit an adjustment to specific brightness ranges in your image (via the Shadows, Midtones and Highlights options). Instead of simply choosing the colour that you want to shift your image toward or away from, variations will present you with the visual results of making such changes so you can simply click on the version of your image that you thinks looks better than the current one.
The Colour Balance choice is often used as a replacement for Variations because it’s available as an Adjustment Layer, which allows for more versatility when adjusting an image. Moving a slider to +15 or -15 is approximately the same as one click in the Variations dialog.
The main issue with Colour Balance and Variations is that the definition of their Shadows, Midtones and Highlights are rather broad, which means that they aren’t always going to isolate an area with enough precision to make them especially useful.
When you need to isolate an area based on a colour instead of brightness, you’ll need to use a Selective Colour adjustment. After choosing a colour from the Colours pop-up menu, you can adjust the amount of Cyan, Magenta, Yellow and Black that makes up that area.
Keep in mind that making an area less cyan will cause it to shift toward the opposite of cyan, which means it will head toward red (since it’s across from cyan in the colour wheel); making an area less magenta will cause it to appear more green; and making it less yellow will cause it to look more blue.
If you have trouble remembering these relationships (because you don’t have a colour wheel tattooed to your arm), then choose Window>Info. You’ll see that CMY appears on the right side of the palette and the opposites of those colours appear on the left side of the palette.
Selective Colour is particularly useful in the following circumstances:
• By choosing White and adjusting the black slider, you can control how bright the highlights are on the shiny objects such as diamonds, chrome, or water. Brightening these areas make the subject matter extra shiny and it “jumps off the page”.
• By choosing Blacks and adjusting the Cyan, Magenta and Yellow sliders, you can shift the colour of any dark shadow area in an image.
If you want to shift the overall colour of an image with Levels, you’ll first have to choose a colour from the Channel pop-up menu to indicate which colour you’d like to shift your image toward or away from. The middle slider is usually the most effective at shifting colour and will often produce a result that’s preferred to using the Midtones setting in Variations or Colour Range – because it causes less of a shift in the highlight and shadow areas.
Curves is by far the most versatile choice in the warm/cool category of adjustments because its not limited to isolating shadows, midtones and highlights, and it allows you to isolate any brightness range within your image. Along with this control, however, comes complexity that makes Curves one of the most difficult adjustments to learn and master.
Both Levels and Curves offer three eyedroppers that can be useful when attempting to colour-correct an image. The idea is to find areas that measure the exact extent of colour contamination by clicking on areas that should look grey but currently look to warm or cool. The two adjustments in this category are designed to allow you to re-interpret the individual colours that make up an image by isolating them independently adjusting three qualities of the colour.
1. Changing the basic colour by moving it around the colour wheel clockwise or counterclockwise-known as changing its hue;
2. Changing how colourful it is by pushing it toward the centre or outer edge of the colour wheel-changing a colour's saturation.
3. Changing how bright it is-adjusting its lightness-which is not part of the colour wheel because the basic wheel doesn’t include the full brightness range of colours you can create in Photoshop.
This type of adjustment is the most useful for changing the general appearance of isolated areas, such as making a blue sky a deeper blue, changing the colour of a car, or making yellow/green grass look greener. Two adjustments-Hue/Saturation and Replace Colour-take this approach to working with images and both of them are designed to easily isolate areas of an image.
The Hue/Saturation dialog can isolate areas based solely on their basic colour. It cannot tell the difference between areas that vary in brightness or saturation. To isolate an area, start by choosing a hue from the edit pop-up menu at the top of the Hue/Saturation dialog. This makes a group of grey bars and tiny sliders appear in between the two horizontal bars at the bottom of the dialog. Photoshop will only change areas that contain colours that appear above the grey bars: it will apply the adjustment at full strength to any colours that are above the dark grey bar and then cause the adjustment to fade out as it extends into the colours that appear above the light grey bars, so that there isn’t an abrupt transition between the area you're adjusting and its surroundings. You can fine-tune the range of hues being isolate by moving the tiny sliders that define those grey bars at the bottom of the dialog.
Once you’ve isolated an area, you can move the Hue slider to change its basic colour, the Saturation slider to control how colourful the area is, and the Lightness slider to brighten or darken it.
Replace colour offers the same adjustment controls found in the Hue/Saturation dialog and only differs in the method used to isolate areas and prevent the adjustment from affecting the entire image. The Replace Colour dialog can isolate areas based on a combination of colour, saturation and brightness (unlike Hue/Saturation, which is limited to isolating areas based on basic colour while ignoring difference in brightness and saturation). Replace Colour therefore can isolate areas that Hue/Saturation wouldn’t be able to tell the difference between.
To isolate a range of colours, start by lowering the fuzziness setting to zero and click on the colour you would like to isolate within your image.
Then to expand the range of colours being isolated, hold shift, click on additional areas within your image to add those colours to the selection and adjust the fuzziness slider if you would like to allow Photoshop to work within the areas that vary from the ones you clicked on. Once you’ve isolated an area, you can shift its colour by adjusting the Hue/Saturation/Lightness sliders or by clicking on the Result colour swatch and picking the colour you desire.
The Channel Mixer allows you to mix the Red, Green and Blue channels that make up an image. This type of image adjustment is often used to push detail into one channel that lacks detail. It can also be used to shift colours-similarly to what Levels and Curves offer (by switching between the Red, Green and Blue Channels)-which can be useful when you need to exaggerate the difference between different colour areas in an image. Note: I recommend that you only use this advanced adjustment when you have lots of experience working with the contents of the Channels palette and know how those pieces affect the overall appearance of an image.
The Gradient Map adjustment does a rather simple and unusual thing: It first converts an image to greyscale and then replaces the shades of grey in the image with the colours that show up in a gradient.
The main problem with using Gradient Map is that you can easily end up with bright colours across the full range of the image, which will trash the contrast of the image. To prevent that, apply the adjustment by choosing Layer>New Adjustment Layer>Gradient Map. In the New Layer dialog, set the Mode pop-up menu to Colour and then click OK to get the Gradient Map dialog. This will prevent the adjustment from affecting the brightness of the image.
I often use the Gradient Map command to transform a backlit image into one that looks like it was taken at sunset. All you have to do is create a gradient that starts with black and slowly fades to orange and then yellow.
Match Colour will attempt to make a selection in an active image look similar in colour and contrast to a second active image (chosen from the Source pop-up menu). Once the two images match, you can adjust the image Options sliders to fine-tune the results. If you want Photoshop to analyse a small portion of either image, just make a selection in the image before applying the adjustment and turn on the appropriate checkbox near the bottom of the dialog.
As users push their skills levels from beginner through intermediate to advanced, they also tend to shift the adjustments they use on their images. Beginners start with adjustments that are easy to understand and use, but that may be limited in functionality. As users become more proficient, they’re more willing to give up some ease of use to gain versatility. The point is that it’s rare for users to need the full list of adjustments because many perform the same function and only vary in precision, flexibility and ease.
At the very least, I hope this demystifies the mind-boggling arsenal of colour adjustment tools. At best, perhaps it will nudge you into taking time to refine your adjustment skills and ultimately help you get your colour adjustment tasks completed quickly and efficiently.