Digital Photography One on One Video Tutorials

DP 1on1 E010 – Light Ratios

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In this episode of Digital Photography One on One, Mark Wallace [] explains light ratios in the studio.

Question Answered:
1) How do I determine my light ratio?

Bonus Material

Equipment used in this video:

Model: Megan Accordino

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One thought on “DP 1on1 E010 – Light Ratios

  1. Russell MacDonald

    Hi Mark,

    I’m not sure you are aware that your tutorial on lighting ratios uses a different definition of the ‘lighting ratio’ than what is taught in photography schools.

    I measure my lights exactly like you do. It’s only the formal definition of ‘light ratio’ that is in question.

    The tutorial defines the lighting ratio as the ratio of the power of the two lights, but that is normally called the ‘incident light ratio’. This is not the same as the ‘lighting ratio’ as defined in classical photography texts.

    In photography texts, the ‘lighting ratio’ is defined as the ratio of the highlights to shadows on the subject (also known as the reflected light ratio).

    The fundamental reason for the difference is that when you use two lights, there are places where the lights overlap on the subject. In these overlap areas the reflected light is equal to the SUM of the two lights.

    For instance, if you use two lights of equal power, anywhere they overlap, the reflected light will be doubled. So, in the photography textbooks, when the incident light ratio is 1:1, the classical ‘lighting ratio’ by definition will be 2:1.

    If you use the definition of ‘light ratio’ given in the tutorial, then there will always be a one stop difference when comparing your work to other photographers.

    For instance, if you look at an image in a textbook that is labeled as having a 3:1 lighting ratio, it will have been produced by a 2:1 incident light ratio, (again, because the two lights add where they overlap).

    Another example: If you set your main to f/8 and your fill to f/16 (two stops different) your incident light ratio is 4:1, but your ‘light ratio’ as shown photography textbooks will be 5:1.

    You can also measure the light ratio by turning on both lights and using your incident meter to measure the brightest area (where both lights overlap) and the darkest area (where only the fill light falls). You will find that the ratio between the two measurements will be the correct ‘light ratio’ as defined by the textbooks.

    Again, this only becomes important when trying to compare your work to other photographers.

    Please let me know what you think.