Digital Camera Exposure Level, Color Contrast

When we use slides, the exposure level has direct and impossible to modify consequences in the tone, saturation and brilliance of the colors. While with a negative the image's final brightness depends on the intensity of the printing light, with slides the exposure level influences on the brightness of the projected scene. The films sensitivity indicates that the density obtained in a zone that receives a strictly correct exposure level reproduces the corresponding zone of the image with a brightness similar to the original. If the exposure level is greater, the corresponding scene gets lighter, if lower, it appears darker. This implies that the color saturation varies with the exposure level. Inside the exposure latitude limits, a density superior to the optimal reduces the saturation towards black; a lower density lightens, reducing the saturation towards white. On the underexposure limit, the pigment is too dense and the color looses it's tone , appearing practically black; on the overexposure limit, the pigment barely has density, and the color is almost white, destroying it's tone. Since the pigments are better when they have a certain density, the color's maximum saturation is reached for a slightly lower to OK exposure level.

Color Negative

Now let's imagine that what we want to obtain is a positive image on paper, without a limit to the number or size of the prints. This lets us, like in black and white, decompose the process in two phases: a brightness and color registration, and it's posterior printing to the desired size. We have seen that reversible film responds to the need to obtain positive and projectable images in one step. This implies great technical complexity, high characteristic contrast, low latitude and impossibility to correct image color and density after the exposure. These inconveniences, which are important to obtain quality slides, are repeated in the printing process. It's clear that if we want to obtain prints on paper it's necessary to use a less complicated process to avoid these inconveniences, even though it means giving up to a direct positive image. The negative-positive color reproduction system responds to this principle.