Wednesday, September 8, 2010

Photo of the Day: "Bighorn River Near Dusk"

Nikon D90, 17-35mm
f2.8, 17mm, f13, 0.6 sec. Handheld, ISO "Lo1" (ISO 100 equivalent), no flash or VR. Aperture-priority exposure mode, landscape scene mode with matrix meter engaged.

This was taken a few hours before yesterday's photo of the day and only about 50 meters away.

A few notes. The camera settings were dictated by one variable: shutter speed. There is a certain sweet-spot with moving water, which varies by the speed of the water. Shutter too slow and it turns to fog. Shutter too fast, and you lose the sense of movement. Six-tens of a second turned out to be the best speed for this shot. Handholding was accomplished by bracing against the handrail of the bridge from which this shot it taken.

Once I determined .6 sec. was the optimum exposure length, I found the camera wanting f16 at ISO 200, the base ISO on the D90. Furthermore, I should have dialed in some negative exposure compensation: the pink/orange highlight of the cloud is dangerously near blowout.

ISO "Lo1" and f13 was the best I could do since I didn't have an ND handy. I'm left dealing with a few things that each slightly degrade image quality here, but hopefully the cumulative effect isn't too bad.

At ISO "Lo1" the D90 loses some highlight control, which is why those clouds are so near blowout. f13 is just starting to get soft from diffraction. Fortunately, there isn't enough near detail for a hint of blur to become too much of an issue.

I don't have post-processing information available for this photo, but I have two other issues I'd like to touch on.

The first is exposure blowout, when things get too hot for the camera settings and turn to mush and white. Newer Nikon bodies have a setting called Auto D-Lighting, or as Rockwell refers to it, Automatic Dynamic Range, which tries to reduce this problem. Figures 1, 2 and 3 show a portion of this image with exposure reduced four stops in Lightroom, and a portion of another blown out image taken with a D80, both before and after that same four-stop reduction.

Figure 1.                                    Figure 2.                                    Figure 3.

The D80 lacks ADL/ADR, whichever you prefer to call it, and it shows. The D90 image, while on the bloody edge of overexposed, retains a color-correct falloff toward blowout. That is D-Lighting at work, making th best out of a difficult situation. With the landscape scene mode (which jacks up saturation) and ISO "Lo1" set, this is pushing the camera pretty hard. But look at the D80 images: there is zero color falloff once you hit blotto overexposure: it just turns straight to white. Also note that the D80 does have a setting in the RETOUCH menu for "D-Lighting," but it doesn't make nearly as much of a difference as the in-camera routine of newer bodies.

The other point I wanted to touch on, actually complain about, is metadata handling in Adobe products. Lightroom reads today's image as ISO 100, which is close enough to correct for me, but Bridge just throws up its hands and displays a blank in the ISO spot for metadata. Photoshop also reads ISO 100. Bridge incorrectly says this was taken in program mode (it was really in aperture-priority mode). Lightroom is stingy about telling me whether or not I used flash. You get the idea: none of these three programs consistently tells me everything I need to know. End rant.

While I have misplaced my post-processing notes, I do have the original photo:

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