For those curios about what I'm speaking about --- although I have
the feeling that I'm alone in this boat :) --- I'll highlight bellow
some outputs of my prototype.
All the outputs are available at the link below, one folder per
RAW image, and for each resulting image one JPEG (several hundred KiB)
and the uncompressed `PPM` / `PGM` (multiple MiB's in size). (All the
images linked in this email are JPEG's, although they contain in the
name `ppm` or `pgm`.)
(Please don't judge these images aesthetically because they are
mostly experiments.) :)
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/
For exposure assessment one could look at the following image.
White is overexposure (the value in any of the channels is larger than
99% of the maximum possible value), and black underexposure (less than
1%). The other 12 gray shades are obtained by combining 4 levels for
each channel.
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/dsc_2401/exposure-z.pgm.jpg
The original can be seen at:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/dsc_2401/preview-rgb.ppm.jpg
The same over- and under-exposure is also overlaid on a color
"sketch" of the image, at the following link:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/dsc_2401/blinkers-rgb.ppm.jpg
The main information I get out of this --- except the obvious
over-exposure in the sun and its reflection --- is that the tree
branches and the other side of the river are under-exposed, thus I
won't be able to get out any color for those parts. (Obviously the
scene latitude is larger than the exposure latitude of this camera,
Nikon D3100.)
Another example is the following:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6196/exposure-z.pgm.jpg
The original being:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6196/preview-rgb.ppm.jpg
Although it is obvious from the original that the light-bulb is
completely over-exposed (and a small part of the bow), it's harder to
notice with the naked eye that almost all specular highlights are
overexposed.
Interesting to see in this image is also the sharpest parts of the image:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6196/sharpness-rgb.ppm.jpg
Thus switching to the sharpness evaluation, see bellow two small
variations of the same scene in which I've played with manual focus
(trying to "guess" the hyper-focal value on my lens, because I wanted
to include the forground in focus also).
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6226/sharpness-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6229/sharpness-rgb.ppm.jpg
Looking at the two originals (linked below), even at 100% it's
harder to decide which is sharper. However on closer inspection of
the previous two "helper" images I could conclude that 6226 has better
focus of the foreground, while 6229 has better focus of the distant
shore.
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6226/preview-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp6229/preview-rgb.ppm.jpg
For other three tough decisions see the following "siblings"
bracketed in a hurry at 0.7 EV:
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5653/preview-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5654/preview-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5655/preview-rgb.ppm.jpg
Their exposure (seems the meter was dead-on):
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5653/exposure-z.pgm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5654/exposure-z.pgm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5655/exposure-z.pgm.jpg
Their sharpness (seems the second one is less fuzzy, however not by much):
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5653/sharpness-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5654/sharpness-rgb.ppm.jpg
http://data.volution.ro/ciprian/bdf753de58c560bc/6d20367506baa6fb/_igp5655/sharpness-rgb.ppm.jpg
As you can see I'm not searching for a magical decision device,
just something to help me assess the alternatives, pointing me to the
parts of the picture that need my attention (especially in the case of
focusing errors or camera shake.)
Hope I was able to exemplify what I was after. :)
Happy new year!
Ciprian.
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