If you'd like to know more about the essential role that light plays in photography, then you’ll love our course, A Photographer's Guide to Light. In this lesson, you’ll find out what exactly contrast is, and how it works.
A Photographer's Guide to Light: Contrast
The world looks a lot different on a clear, sunny day compared to an overcast day. Why? The answer is contrast.
What Is Contrast?
In photography, contrast is the difference between the light and the dark parts of an image; it is this difference in luminance (brightness) or colour that makes an object or its representation in an image distinguishable. Contrast is measurable.
In this image, you see a checkerboard pattern with black and white squares. About half this image is as black as your display will allow, and the other half is as white as your display will allow. If you were to view this on a different display, you might see more or less contrast depending on the quality of the display.
If we reduce the contrast, then a grey tone is introduced into the blacks, as grey lies between black and white. The difference in luminance between darkest and lightest is reduced: there's less contrast.
A similar thing happens if we take the white squares and darken them from a bright white to a grey tone; the result is lower contrast.
If both the black squares and the white squares were pushed towards grey, then of course the whole image would become grey and you wouldn’t see any squares at all, and that shows us that contrast is really important as without it, you can't define an image.
In the real world, everything you photograph will have at least a little contrast.
Hard Light and Soft Light
Let's look at the two ends of the spectrum: high contrast and low contrast. The way to tell the difference is to look at the shadows.
High-contrast light will result in a shadow that has a sharp and well-defined edge, like the shadow in this picture of an apple. This is what you typically get with the sun on a clear day and no clouds in the sky.
These types of shadows with well-defined edges are usually called hard shadows, and the lights that produce these shadows are called hard lights.
Let's imagine that the clouds roll in and obscure the sun. The shadowing on the object will be very different. In this situation, the sun's light scatters through the clouds and hits the object from many different angles. This is low-contrast light.
The result is a shadow with a smoother gradation between the area that's fully in the light and the area that's fully in the dark. This is called a soft shadow. The lights that produce these types of shadows are called soft lights.
Size Relative to Subject
The main difference between a high-contrast light and a low-contrast light is its size relative to the subject. A high-contrast light is small relative to the subject, and a low-contrast light is large relative to the subject. The sun is huge, but because it’s so far away it acts as a small lighting source.
The clouds on an overcast day are much larger relative to the objects on earth, and they diffuse the light from the sun and bounce it around, acting like a large lighting source. The illustration of the sun and the clouds is useful as the same idea applies to photographic lights.
Take a small light and shoot it through a much larger material, and you get a very similar result. The light from the flash hits the material and is scattered around. This material now becomes the light source, and because it's larger, the light will hit the subject from many different angles. You can take a high-contrast light and modify it to get a low-contrast light.
To make a low-contrast light into a high-contrast light, just think of the sun. You know that the sun is huge, but it's really far away. Take a low-contrast light source, like a soft box, and move it far away, and it becomes a high-contrast light.
A Light Source Isn’t the Only Means of Creating Contrast…
The contrast of a light source is only one of the factors that determine an image's contrast. If you take a bare flash and use that as your only lighting source, you’ll get high-contrast shadows, but does that mean that your image will be high contrast? Not necessarily, and the reason is we don’t know how much of the shadow you’ll actually see. If the flash is very close to the camera's lens, the shadows will be behind the objects you’re shooting. This means that you don't see very much of that shadow.
If the image was made up of objects that were all around the same tonal range—as above—this wouldn’t make a very high-contrast image.
Move the flash away from the lens, and you start increasing the contrast of the image because now you’re seeing more of that shadowing. The same thing applies to a low-contrast lighting source. By altering the composition, exposure, and post-processing, you can get a high-contrast image from a low-contrast light, and you can get a low-contrast image from a high-contrast light.
The main thing to remember is that high-contrast lights always produce hard shadows, and low-contrast lights always produce softer shadows.
More Resources on Light From Tuts+
About the Authors
David Bode created the video course that includes this lesson. Dave is an expert on video and audio production, and he lives in the upstate New York area. He works as a camera operator, editor, inventor, motion graphics designer, recording engineer, and studio musician.