Dana : A Fine Line Between Beauty & Glamour. Blamour?

[Robert Mitchell]

Think of lighting as a contrast control.

If you're working with one light, you position that light and create highlights and shadows. You can move the light up, down, left, right to control the contrast and transitions from specular to highlight, highlight to diffuse, diffuse to shadow and shadow to black.

If you place your key light and add a fill light (true fill at camera position), you're lifting shadows and decreasing contrast. If you have a strong shadow under the chin you can add a light source or reflector to further lift those shadows, thus decreasing contrast.

If you have a small white room and you have a main light at camera left but find that you're getting some return from the right side wall, that is decreasing contrast. You can then subtract light with a cutter or gobo and this increases contrast.

Regardless of quantity of light or contrast, you adjust exposure accordingly based on where you want your highlights to fall. This only applies to digital. With film you had so much latitude that you didn't have to be concerned with a blown highlight and it was much more important to expose for the diffuse value. Exposing for highlights with film would give you a very muddy mid tone.

 

[Eye-level]

What about the principle of less light? All other things equal the less light on a subject the less contrast there will be. Consider the case of a white cube on a piece of black velvet. Though the black velvet cannot be made lighter, the cube can be made darker, by reducing the amount of light.

And what about this dogma of the perfect exposure being the minimum exposure just short of underexposure? Is it a film deal? Why doesn't digital deal with highlights very well?

 

[Robert Mitchell]

What about the principle of less light? All other things equal the less light on a subject the less contrast there will be. Consider the case of a white cube on a piece of black velvet. Though the black velvet cannot be made lighter, the cube can be made darker, by reducing the amount of light.

And what about this dogma of the perfect exposure being the minimum exposure just short of underexposure? Is it a film deal? Why doesn't digital deal with highlights very well?

I'd love to see the source for this principle of less light. That's not correct at all. If all other things are equal, including exposure, then contrast won't change.

If I have a light on my subject that produces f/16 and then reduce the quantity of light by 2 stops so that it produces f/8, contrast does not change at all. If it's changing then the light source has moved.

If you have a white cube on black velvet and want to render the cube as white then the velvet can't be black. If you want to render the velvet as pure black then the cube will be gray, not white. In this example, the perception of change in contrast occurs because you're sliding the exposure window around depending on where you want your mid tone. If it's a properly placed mid tone then neither the white cube or black velvet will render correctly but since contrast is really the difference between highlight and shadow, that range remains the same regardless of the quantity of light.

With digital, the key is to expose for highlights and to retain detail. All other values fall where they may. This is because in the digital world it's just like recording digital sound. When the level clips, you get distortion. With digital imaging, when highlights clip they are lost and can't be recovered.

If you expose for lower values then highlights and something like a white wedding gown will never be white and the chances of introducing noise are much greater if you underexpose and then have to raise exposure in post. You can further adjust black point to create the illusion of a wider dynamic range.

Digital sensors get better and better every day and the D800 or a medium format camera are examples of incredible dynamic range, but with most digital cameras the dynamic range is so limited that you can't have white and black at the same time and in terms of 'picking your poison', I'd rather push my highlights and have to adjust my black point rather than underexpose my highlights and raising overall exposure. Typically, DSLR's have more latitude above the midtone than below. Below the mid tone, black and shadows get crushed together and become a black mush.