The Professional Photoshop Book - Volume 7 2015

Pro tricks for mastering colour

24 The Professional Photoshop Book

UNDERSTAND AND USE

MAKE SENSE OF PHOTOSHOP’S COLOUR GRAPHS AND

LEARN HOW TO USE THEM TO ENHANCE YOUR IMAGES

HISTOGRAMS

T

he histogram is an incredibly powerful

tool for monitoring and editing colour in

your images, but many Photoshop

users are put off using it by its seeming

complexity. The truth is that histograms are

relatively simple to understand once you’ve got

a good grasp of basic colour theory and

Photoshop’s other colour tools, and using the

histogram enables you to take complete control

of the colour and contrast in your image so that

you can achieve professional results.

At its most basic, the histogram is simply a

graph, which shows you how dark, light and

midtones are balanced in your image. The left

hand side shows the darkest tones, the middle

the midtones and the right hand side the

lightest, brightest tones. You can display the

histogram at any time by going to

Window>Histogram, and control how the

histogram shows you the colour and tonal

distribution in your image by using the

drop-down menu in the Histogram panel to

select RGB, Colors or Luminosity. You can do

this for the whole image, or make a selection

and view an individual histogram for this part of

the image alone, which is particularly useful if

you’re adjusting the colours in a composite. You

can also get a split view of the individual Red,

Green and Blue channels in your image

underneath each of the types of histogram.

TYPES OF HISTOGRAM

AND HOW TO USE THEM

RGB HISTOGRAM

The main RGB histogram gives you an

overview of the distribution of lights, darks and

midtones in an image. There is no such thing

as a ‘good’ histogram, but there are a few

things to keep in mind. If you want a dark

image your histogram should stack to the left,

and if your image is mainly light-toned, it’s

stacked towards the right, while a midtone-

based image should form a loose bridge shape

with the peak in the middle. If your image has a

strong contrast of light and dark it should form

a U-shape dominated by peaks on either side.

COLORS HISTOGRAM

The Colors histogram shows you the

distribution of light and dark, plus the

distribution of colours in your image. When a

painting’s colour scheme just looks ‘wrong’

the Colors histogram can provide you with the

reason why. You can instantly see which

colours are over and under-represented and

how they relate to the intensity of tones in the

image. Remember – warm light, cool

shadows; cool light, warm shadows!

LUMINOSITY HISTOGRAM

The Luminosity histogram monitors the

brightness of your image, and to do that it takes

account of how we see levels of brightness. It’s

a quick and easy way to check if an image is

over or under-exposed. It looks at your image

pixel-by-pixel and determines whether each

one is mainly red, blue or green – our eyes are

more sensitive to brightness changes in green

light than they are to blue or red. It’s a useful

resource when you’re matching light or tonal

levels between multiple photos in a composite.

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