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Tuesday, February 17, 2009

Aesthetics Of XDR

Using Extended Dynamic Range techniques judiciously will keep you from taking a good thing too far

This Article Features Photo Zoom

1) LDR image

HDR imagery is expanding today’s photographic aesthetics. Identifying the characteristics of contemporary HDR images will help classicists and pioneers alike. The basic ingredients are desirable for both sensibilities, but in varying combinations and to different degrees.

Pronounced Shadow And Highlight Detail. Preserving significant amounts of shadow and highlight detail, even in images containing extreme contrast ranges, is something long sought after and continually improving in photography. Prior limitations in the medium have established a conventional appearance for photographs that now needs to be reconsidered—first, in light of the way the eye sees at a glance; second, in light of the way the eye sees adaptively over time; and third, in light of the way we might like to represent a scene expressively. Excessive recovery can alter large-scale contrast ratios unnaturally and in extreme cases may yield localized solarization.

Accentuated Edge Contrast. In an effort to preserve midtone separation after extreme dynamic range compression, edge contrast is accentuated. This produces dark lines and bright halos, typically feathered rather than hard-edged. As they intensify, they begin to drive images away from a classic smooth, continuous-tone appearance.

Accentuated Texture. Boosting midtone contrast, in addition to contouring and haloing, also brings an exaggeration of texture. This tends to be particularly pronounced in shadows and highlights, but it can be found in midtones as well. What was initially low contrast with little separation can become more contrasty with significant texture.

Increased Noise. Separating signal (texture) from noise (grain or noise) can challenge even the most sophisticated software. When texture is increased, often noise also becomes pronounced.

Smoothed Texture. Aggressive attempts to subdue noise may leave transitions between closely matched tones excessively smooth with a significant reduction in texture. Some applications make real-world or captured information look synthetic or rendered.

Saturation Distortions. Brightness changes bring saturation shifts with them. When shadows and highlights are significantly compressed, saturation also shifts, sometimes yielding an unnatural appearance, typically but not exclusively oversaturated.