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Lighting & Contrast

The basic problem in photography lighting is contrast.

Contrast could be defined as the difference between how dark the darkest part of the scene is compared to how bright the brightest part of the scene is.

When purchases a television, computer monitor or display device the manufacturer will often gives specification on the “contrast ratio”. The contrast ration might be 1:400 or 1:1000 or even 1:10000.
A 1:400 contrast ratio means brightest part of the picture is 400 times brighter than the darkest part of the picture. Of course the majority of the image fits somewhere between the darkest and brightest spots. So you could say the different degrees of brightness between 2 and 399 are the shades of grey.

In the real universe the contrast ratio between the darkest cave and staring directly at a sun is probably incalculable.

At any given time, the human eye is capable of perceiving a contrast ratio of about 1:10,000. The human eye is capable of adjusting to dark or light environments. The full range of the human eye is probably about 1:1,000,000.  Yet the human eye has it’s limits. We all know that if you stare at something too bright such as the sun, you can go blind. Like wise, certain animals (such as cats) are capable of seeing clearly in low light environments which for the human eye would seem completely black.

Well the first thing to learn about photography lighting is that a camera has a contrast ratio range the is far smaller than a human eye.

When taking a photograph, If an area in a scene is so bright that it’s beyond the cameras contrast ratio, the area appear white. If an area in the scene is too dark for the camera’s contrast ratio, the area on the photography appears completely black.

Area of a photograph that were too bright for the camera’s contrast range are completely white and are called “overexposed” or “burned out” area.

Area of a photograph that were too dark for the camera’s contrast range are completely black and are referred to as “underexposed” areas.

Histograms

histogrambasic

A histogram is graphical representation of the exposure of a pictures. Areas on the far left of the histogram are underexposed and completely black. The area of the far right of the histogram are over-exposed or completely white. The areas in the middle of this histogram are within the cameras contrast range and represents shades of grey which can be clearly seen.

There are three styles of high contrast photography where the limited range of the camera contrast are used intentionally to produce an artistic effect.

Low Key Photography

Low key photography is dark. The photographer purposely creates a high contrast lighting situation and sets the cameras exposure for brighter part of the scene. The result is the shadows are completely black. This is purposely underexposing area of the photographic scene.


A histogram for a low key photograph will have a large portion of the graph to the far left, indicating the large portion of the picture is underexposed.

histolowkey

High Key Photography

High key photography is bright. The photographer purposely creates a high contrast lighting situation and sets the camera exposure for the darker areas. The result is the highlights in the photograph are completely white. This is purposely overexposing areas of the photographic scene.


A histogram for a high key photograph will have a large section of the graph to the far right indicating that the majority of the photograph is overexposed.

histohighkey

Silhouette Photography

Silhouette photography is a type of photography which utilizes a high contrast back lighting situation. The photographer sets the exposure for the background. The result is the subject is completely underexposed and blacked out while the background (being in the cameras contrast range) is clearly visible.  (Note: Only one of the examples pictures is my own.)


A histogram for the silhouette photograph will have a spike on the far left of the graph indicating that a portion of the photograph (the subject) is underexposed.

histosiloutte

Average Exposure Photography

Despite the three artistic styles of photography mentioned above, in most photos the photographer attempts to keep the scene within the contrast range of the camera. In other words, he wants everything in the scene within the exposure range, nothing overexposed and nothing underexposed.

A histogram in a standard photograph does not have any of the graph on the far right or far left. This indicates that every portion of the scene was within the contrast range. Again, nothing is overexposed and nothing is underexposed.

histonormal

In the real universe, the contrast between the brightest spots in scene and darkest spots in a scene are a far greater range than a camera is capable of recording. The handle this there is a whole gambit of photographic lighting equipment and different lighting techniques to adjust the contrast in the scene so it is within the limits of the camera’s contrast range. That will be the discussion in the next article.

Mike Williams

Austin Fine Art & Glamour Photography

One Comment

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  1. goldfishka / May 9 2011

    Really helpful!

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