Contrast and color casts
It is all about the enviroment
In some of my previous blog posts I have talked about diffusion and its effect on the contrast of an image from what I term “environmental bounce.” I have two photographs here that I think will help demonstrate and explain what is happening. When we diffuse our light we spread out the beam of the light. The light bounces around the room and various surfaces in the room become secondary sources of illumination. These new sources help fill in the shadows making them less dense (lowering contrast, but not softening the shadow edge transition unless the diffusion is larger than the original light source). If the surfaces are not neutral in color, they can also add a color cast to the photograph.
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In this first photo the light is an Interfit Photographic 65-inch (across the opening, 7-foot measured along the arc) silver parabolic umbrella. The light is an Interfit Honey Badger flash mounted deep into the umbrella to focus the light making it very directional (see my previous article on Parabolic Umbrellas). In the reflection in the eye you can see the bright catchlight concentrated in the middle of the umbrella, but you can barely make out other items in the room (the environment).
In this next image the modifier is still the same silver 65-inch umbrella at the same distance. But now the lamp head is pulled out of the umbrella to defocus and spread out the light. The light also spills out around the edges of the umbrella, lighting up the walls, ceiling, and most notably the wooden floor. The environment is much more noticeable in the reflection and has much more effect on the photograph.
The difference here is what I mean when I talk about environmental bounce. The first image is more contrasty and cooler in color. The second image is less contrasty with the pores in the skin being filled in a bit more and it is warmer in color due to the light bouncing off the wooden floor. You can better see the difference in color in the stacked pair at the right. A closer view of the eye appears below. All the things you see in there, the floor, light stands, photos hanging on the walls, the ceiling, etc. all contribute to the look of the photograph.
The smaller and brighter your space, be it your living room, spare room, garage, studio, or wherever, the more effect the environment will have on your images. Outside at night in an open field or in a warehouse size studio with black walls, floor, and ceiling there would be very little difference. In a small studio you can use baffles like grids, snoots, and barn doors on the lights or black foamcore sheets around your subject (negative fill) to control contrast and color casts.
Thanks again for following along! Wishing you a happy and joyous holiday season and a bright new year!