Tuesday, July 30, 2013
Keeping It Real With HDR
How to use HDR software to maintain appropriate contrast, overcome the limitations of the sensor and bring out detail—without overdoing it!
7) Beware halos where dark objects meet bright backgrounds. This is another dead giveaway of an overbaked HDR. HDR packages have become much better over the past few years at controlling halos, but they can still be an issue, particularly if you compress the tonal scale too far.
8) When blending shadow and highlight regions into a believable whole, gradients can be your friend. Our visual system is very sensitive to abrupt change, but quite insensitive to gradual change. For example, we're sensitive to the abrupt change of color and density at the boundary between highlight and shadow regions, but rather insensitive to gradual changes in density within each region. By employing a digital graduated ND tool, such as the one found in HDR Efex Pro 2, you can place both the shadows and highlights relatively close to midtone, then blend them in a way our visual system finds believable.
Imagine a simplified example, in which the top half of the frame is filled by sunlit mountains and the bottom half of the frame shows shadowed flowers. You place a digital graduated ND filter over the image, with the transition zone of the filter centered over the dividing line between shadow and light, which lies in the middle of the frame. Now let's trace the changes in density caused by the filter as you examine the image from top to bottom. In the highest quarter of the frame, the filter has made the image uniformly darker. In the next quarter of the frame, which is still sunlit, the image gradually gets lighter as the virtual filter begins its transition from dark to clear. The beginning of the third quarter marks the beginning of the shadow region. The filter's transition from dark to clear continues in this quarter, so the shadow is darkened most at the very top of the quarter and not darkened at all at the bottom as the transition zone ends. The bottom quarter of the image is unchanged. Both the bottom and top quarters can be rendered close to midtone, but the transition from highlight to shadow still looks natural because there's still a strong color and density change at the shadow boundary.
In the days before digital, a "film aesthetic" ruled. A photograph was deemed "realistic" if it looked the way film originally recorded the subject. For a high-contrast scene, that meant bright highlights and inky black shadows. The invention of digital photography gave photographers greater control over highlight and shadow density, and the film aesthetic began to erode. Today's HDR software gives you total control over the density of every part of your frame, from the deepest shadows to the brightest highlights. This unprecedented power has completely overturned the old film aesthetic, but a new aesthetic hasn't yet become widely accepted. I've worked diligently to prepare a realistic-looking HDR rendition of a high-contrast scene, one that closely resembled what I saw, then had experienced photographers tell me they thought the result looked quite unnatural. During this period of flux, your best guide to "realistic" will be your bracketed set of images, your knowledge of how our visual system processes high-contrast scenes and your own good judgment.
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