Controlling Contrast

Article by Ben Fewtrell

Controlling your contrast is not just for HDR, you will want to control contrast on any image. Adding contrast will help you to create depth in your image. Before we look at how to do this, what is contrast and what happens to your pixels to
create contrast in a digital image?

The word ‘Contrast’ is used to describe the difference between two ends of a spectrum, it could be the difference between political views, the difference in a person’s behavior or even a change in the weather. When used in photography contrast is referring to the difference in luminance, that is, the difference between light and dark. In an image, the lightest light is pure white, and the darkest dark is pure black. Contrast is therefore referring to the difference between the whites and the blacks. Every image is essentially a black and white image, or, in the case of a photograph, it is more a ‘greyscale’ image than one of pure black and white.

So you can see what I mean, open up an image in Photoshop party bouncy castle then select the channels Tab (if you can’t see channels goto WINDOW and select CHANNEL). Here you will see your RGB composite of your image, click on just one of the colors (Red, Green or Blue) and you will soon learn that there is no RED in the RED channel, no GREEN in the GREEN channel and certainly no BLUE in the BLUE channel… Just a mix of black and white to create different shades of GREY. Weird isn’t it? well, it is these three channels that work together to create your colorful image in RGB.

When you adjust contrast you are adjusting the contrast ratio between all of these ‘grey’ pixels. Contrast ratio is normally referred to
in a percentage with the maximum amount of contrast is 100%. A black and white checkerboard is an example of 100% contrast as there is only pure white and pure black.

In essence, increasing contrast will make blacks darker and whites lighter. Open an image on your favorite editing program and increase contrast to full (Usually +100). You will notice that the shadows in your image will become too dark and whites too bright, go the other way to -100 and the opposite will happen, you will have an image with much more even lighting throughout but it will have a cloudy look to it, and this is because the difference between the blacks and whites is much less.

Adding contrast usually adds “pop” and makes an image look more vibrant while decreasing contrast can make an image look duller or flatter.

So what is the best way to add contrast to your images? There are several ways ands sometimes I will use all of them. Each technique will give different results, so give them all a go.

1. Use the contrast slider in your photo editing program (Photoshop, Lightroom, Aperture etc.) They all have a contrast adjustment slider.


2.Use Photoshop Channels – In the channels view just select one channel and make adjustments to the contrast in the ADJUSTMENTS menu. I often use this if I just want to add contrast to certain colors in my image, adding contrast to the RED channel will increase the contrast in colors
containing red.

3. Using Curves – I can use curves in Channels or on my overall image, giving me some really accurate control over contrast throughout my image. By manipulating the curve so the darks are darker and the lights are lighter you will achieve a higher contrast ratio.


4.My favorite… Create an ‘overlay’ layer. You need 2 layers to do this in Photoshop, so if you have just one, press CTRL J (CMD J on a Mac) and  that will create a layer copy. then do this… you’ll love it!

a.Press Ctrl-Alt-Shift-E or CMD-Option-Shift-E on a Mac (It´s the command to take all of your layers and make a merged copy on top of them)

b.Now select the new ‘merged layer’ and change the blending mode to ‘Overlay’. You will immediately notice your image will have high contrast.

c. Now change the opacity to suit. I usually end up around 10% to 15% Opacity as a general rule, sometimes more, sometimes less.
There you have it… now go and add some depth to your images!

Ben Fewtrell is based in Sydney, Australia and has been a keen photographer since the 1990’s. He fell in love with HDR in early 2012 and now processes 95% of his images this way. His main interest is landscape photography and most mornings you will find Ben with his Nikon D800 on the coast of Sydney waiting for the sun to rise… you can find him at www.facebook.com/on3legs or follow his blog www.on3legs.com

Ben also has a free HDR ebook available: http://onthreelegs.com/learn/free-ebooks/