Jim’s question about sharpness – part II

Jim followed up on my reply to his initial question by supplying a couple of sample photos that he was not totally happy with. I won’t reproduce them here since they aren’t my photos, among other reasons, but I will post a few comments and observations.

The two photos were both taken in Yosemite, this summer I think. I took a more careful look at a photo that I think I recognize as being taken along the Tuolumne River in Tuolumne Meadows, with Mt. Gibb in the distance. I have several observations about this photo:

  1. The exposure seems pretty good. Judging from the jpg I saw, it may be slightly underexposed – the histogram stops a bit before the right edge and detail is missing in the shadows of the trees on the right side. (This detail might still be recoverable in the RAW file.)
  2. It looks like the photo was made at a f/22… and this likely is a problem as far as sharpness is concerned. The best aperture for optimum sharpness on crop sensor cameras is generally right around f/8, plus/minus a stop or so. While closing down (e.g. – f/22) would seem to provide greater depth of field, it also emphasizes diffraction effects that decrease the maximum sharpness of the lens. Imagine that you were perfectly focused on an object at f/8; you would likely be obtaining the sharpest possible image of that object. Now decrease the aperture to f/22; this object in the focus plane is now less sharp than it was at f/8. In Jim’s photo, most of the scene is a pretty good distance away… and out of focus due to diffraction. There is little to gain by increasing depth of field, and I suspect that the small aperture is responsible for the fuzzy focus.
  3. In terms of effective framing of the scene, this might be more effective with a tighter crop. There is not enough to hold my interest on the right and left margins or in the foreground, so cropping some of these areas out of the frame might produce a more effective image I think. (It might be possible to go for a squarer format and do most of the cropping from the sides.)
  4. There is a strong blue cast on parts of the water’s surface, probably picked up from the sky. I would adjust this by selecting this area (with a feathered edge) and reducing overall saturation and especially saturation in the blues.
  5. Other parts of the image might be improved by a bit more saturation – perhaps about a 10 or 12 setting in PS.
  6. I would perhaps make a feathered selection of the distant ridge and by levels or curves adjustments give it a bit more contrast.
  7. The other photo is of an impressive scene that almost all Yosemite visitors have gawked at – including me. It was shot along the road descending into the valley from the north, looking east into the valley.

    The difficulty with this shot is mostly the lighting. This is a very difficult place to photograph unless the light is just right, typically very early or late in the day during the summer. It looks to me like Jim was there during the middle of the day when the light is almost directly overhead and is quite harsh – tough conditions!

    I didn’t take a close look at the technical aspects of this image, though it does appear to be fairly well exposed. It may be a bit overexposed, judging from the histogram of the blue channel which picks up the intense blue of the sky – but again there is a good chance that this could be handled in the RAW conversion.

    Dan

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