Exploring and Measuring Light


Matt Smith was recently asked a few questions on light by one of his students. Here were his answers!

Q: In your Red Rock video, you explain that the sunlight is warm and the shadows are cool. My understanding is that cool light, whether it is North light or any light indoors or out, produces warm shadows. What are your thoughts on this?

Matt’s answer:

There are three properties of light. Intensity (brightness), temperature (color), and direction (angle). Outdoors, on a sunny day, there are three light sources. Direct light which is the sun, reflected light which is anything the sun illuminates, and reflected blue sky light. For the second two to exist you need the first one, the sun. No matter what anyone tells you sunlight is warm because it’s a giant ball of fire. The temperature of the sun will change throughout the day but it’s always warm. When the sun shines on something it warms it up. In turn, the shadows will be the opposite or cooler. Maybe not cool (due to reflected light) but cooler than the sun-struck areas. The reading that was taken was most likely influenced by reflected blue sky light (indirect light) which is cool. In direct light the reading would register as warm.

Q: Yes, the sun feels warm on our bodies but measuring the light source with an instrument shows just the opposite (daylight being cool). What are your ideas on this?

Matt’s answer:


Read all the books on color and light, and experiment with tools like a meter, as they will help you better understand what is happening out there. However, at some point, you’ll need to set that all aside and go outdoors and observe how light works firsthand. Believe what you see rather than what some scientific tool or a fellow artist says as you are the one processing the information.

On a separate note, not all light indoors produces warm shadows as some indoor lighting is cool and some warm. And north light is cool because it is indirect light. As mentioned, identify the temperature of the light and adjust the shadows accordingly. Also, a cloudy day produces a cooler filtered light so the shadows would be warmer. The thing is, the intensity of the light is diminished so it won’t be as obvious due to the narrowed contrast.

Another thing to look out for:

Form shadows tend to be warmer than cast shadows as they are influenced by a warmer light source (anything the sun illuminates and warms) and cast shadows are influenced by the cool sky. Keep an eye out for that as a camera often times misses it and/or averages the two. You’ll also note that the lightest lights in the sun-struck areas will actually turn to the cool side but account for a small percentage of the overall light. Same thing with the shadows…..the darkest areas can turn to the warm side.

Matt’s last tip:

Remember, get out there and study these points first hand. That is where the truth lies.


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