Tuolumne River Below Glen Aulin, Morning. Yosemite National Park, California. September 16,2011. © Copyright 2011 G Dan Mitchell – all rights reserved.

Early light on morning clouds above the Tuolumne River Canyon below Glen Aulin, Yosemite National Park.

This is the same bend in the Tuolumne River, located below Glen Aulin and before the river descends toward Waterwheel Falls and eventually the abomination of Hetch Hetchy Reservoir, that was shown in a photograph of late afternoon light that I posted here a few days ago. This time it was early morning. We had been up well before sunrise and had wandered off in various directions to find early morning photographic subjects. My main goals were the cascading water along the edge of this section of the river (a bit of which is visible in the lower portion of the frame) and a granite bowl to the right of this view. As I came over the rise above this area before descending I saw the beautiful sparse clods to the west, probably extending to the edge of the Sierra and still with pastel colors from dawn light.

A technical observation about this photograph. This scene presented a technical challenge in the form of an extremely wide dynamic range between the bright and red-saturated first direct sunlight on the ridge at upper left and the much darker areas of forest in shade along the river and in the foreground. With a digital exposure, in a scene like this one, the primary rule for me is “don’t blow out the highlights.” If I had overexposed the sky the clouds would have turned into pure white, texture-free blotches and that bit of early sun on the rocks would have lost detail and taken on a very strange coloration. However, an exposure that protects the highlights in a scene like this one can leave the shadows nearly black. While it is possible to “fix” that a bit in post, the result is not necessarily very good when the dynamic range is very large. One “traditional” solution would have been to use a graduated neutral density filter (or “GND”) that blocked some of the brightest areas at the top of the frame while not affecting the lower 2/3 or so. But I don’t use them, and in this case the result would not have been totally wonderful since the same filtering that would reduce sky brightness would also make the large granite dome at the right end up nearly black at the top.

So instead of filtering at the time of exposure, I decided that I would use the roughly comparable, but more flexible, “exposure blending” techniques in post. With that in mind I made several photographs at different exposures – some at shorter shutter speeds to avoid the blown out highlights and others at increasingly slower shutter speeds to reveal the shadow detail that my eyes could see but which the camera otherwise could not. During the post-production phase, I selected two of the exposures, one that was as bright as possible but without blowing out the sky and sunlight, and the other two stops lighter to reveal that shadow detail in a way that seemed consistent with what I recall the scene actually looked like. The two source images were carefully adjusted during raw conversion and their two layers carefully aligned. With the darker image (the one with the “good” sky) on the top, I began to “paint” out the mask to reveal the details of the foreground forest, river, and rocks. (In answer to the expected question, this is not the same as HDR. That is a more or less automated process that works in a different way. Exposure blending is typically a manual process that relies a great deal on the photographers judgment and recall of the actual scene.)

G Dan Mitchell is a California photographer whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
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