Light, Science & Magic, 4th edition. By Fil Hunter, Steven Biver, Paul Fuqua.
Published by Focal Press, Taylor & Francis Group.
Light reflects differently depending on the surface that it is hitting.
There are three types of light reflection to consider in photography – direct reflection, diffuse reflection and glare. In some cases there may be a mixture of the three different types of reflection from the subject to be photographed.
Diffuse Reflection – evenly reflected light.
White paper is a good example for diffuse reflection as no matter which direction the light source is coming from the paper reflects the light evenly across the it’s surface. If three cameras where set up around the paper equal distances away from the paper, they will all record an image of the paper with the same brightness. This is because the surface is scattering the light in different directions allowing all three cameras to capture the reflected light from the paper. This type of reflection will have much softer highlights if it has any at all.
Direct reflection – is light bouncing off a surface whilst maintaining its original intensity. A mirror is a good example for producing direct reflection as it will reflect the light keeping it’s original intensity. The brightness of direct reflection also remains the same regardless of distance only the size of the area will change. With direct reflection the light will also bounce of the mirror at the same angle as it hit the mirror. Or in other words,
the angle of incidence equals the angle of reflection
As a result to view this reflection a camera must be positioned in line with the angle of reflection (in other words within the family of angels). However, from any other angel around the mirror the camera doesn’t see the reflection.
Glare – is polarized direct reflection this can be polarized light from source or by the material that it is reflecting off. A good example of a surface that creates polarized direct reflection is water.
Perfectly polarized direct reflected is exactly half as bright as unpolarized direct reflection. Like unpolarized direct reflection it bounces off a surface in the same way; so the reflection can be only seen from the one angle.