Light Travels in a Straight Line

Light travels in a straight line. Light never ‘bends.’ Light never ‘wraps.’ Well, it does around black holes but that’s another book. On earth, light only goes straight.

Light can be reflected or absorbed - but not bent.

Understanding that light travels in a straight line is essential. If you know this, you’ll have a much clearer understanding of how to manipulate light. You’ll know why some lights produce harsh shadows and others create soft shadows. This will empower you to create more beautiful portraits.

Small Lights CAN’T Reach Around Facial Features

Because light only travels in a straight line, a small light creates harsh shadows. The reason is simply that no portion of a small light can ‘reach’ the dark side of the subject’s face.  This is why the popup flash on consumer cameras creates such a harsh shadow - it’s very small. Small flash = harsh shadows.

Large Lights CAN Reach Around Facial Features

If you could draw a straight line from any portion of a light source to the dark side of a face, the shadow will be softened. Therefore, large lights have the ability to soften shadows. A portion of a large light can usually reach around to the shadow side of your subject’s facial features - even if it’s only 25% of the surface of the light.

Summary

If you’re wanting soft shadows in your portrait, you should first consider how large your light source is. If you’re using a small light source (speed light, sun, popup, lightbulb, flashlight), then your portrait will have harsh shadows. If you’re using a large light source (large reflector, umbrella, large diffuser, big white building, entire sky), your portrait will have soft shadows. I’ve spent my life believing that size doesn’t matter but, alas, it does.