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Lighting ratios in photography is something many people seem to find confusing, when in actual fact ratios are very simple to understand.

What are “lighting ratios”?

Lighting ratios are simply the difference in output between your key light and your fill light. These two lights are the main players in providing your photo with the shadow and depth required to make it look dynamic and interesting – just remember that good lighting is about good shadows!

Many people get frustrated with lighting when they start trying to work with 3 or 4 lights all at once. The best way is to set up each light individually. Get the first light to work in the way you want, and then move on to the next.

So let’s say we have set up our first light, take a meter reading and we get f/8, then we set up our second light and also get a reading of f/8 we have a lighting ration of 1:1 – equal output from both. That’s simple enough.

Now let’s make a change to the first light, and change its power until we get a reading of f/11. We have now doubled the light output (+1 stop of exposure is twice as much light) from that light, giving us a ratio of 2:1.

So, a 2:1 ratio would mean that there is a one-stop difference between the lights. A 3:1 ratio would be a stop and a half difference, and 4:1 would be a two stop difference.

Still with me?

Start with the maths – it’s simple

It really is simple:

A factor of 2 (2:) is equal to one stop of exposure.

So, a 2:1 ratio would mean that there is a one-stop difference between the lights. A 3:1 ratio would be a stop and a half difference, and 4:1 would be a two-stop difference.

All you need to remember when working out ratios is that it’s a simple case of multiplication or division by 2.

To work out the ratio 8:1 just divide 8 by 2 – you get 4 – which means 4 stops of difference in exposure.

To work out the ratio of a shot with 2 stops of exposure difference just multiply 2 by 2 – you get 4 – 4:1

Easy!

How is this useful?

Understanding ratios allows you to translate an image in your head to the final shot. Ratios are the foundation on which creative lighting is built.

To illustrate this, here’s a basic outline of the type of images you can expect from the most commonly used lighting ratios:

Play around with ratios, you won’t be disappointed, and your grasp of lighting will extend from procedural to experimental and creative in no time!