swisspace wrote:
> Then I think I am confused in my understanding of using raw , if I use
> olympus viewer I can change the exposure a stop or two up and down and
> adjust the colour etc, but this doesn't help me for example when the sky
> is blown out but the main subject is dark, I would like to underexpose a
> bit for the sky and then overexpose for the subject and combine them, to
> solve the problem I have in this picture for example
>
I wish I could give more specific help, but I don't have that software
and, unfortunately, different converters label controls in different and
sometimes unintuitive ways. The various converters I've tried, PS, RSE,
Canon DPP, Canon Zoombrowser and VueScan, all appear at first to operate
quite differently from their interfaces.
In fact, there are four basic things to adjust in the area of concern to
you. White Point sets what percent of the highest brightness values ahta
are differentiated in the source file are set to pure white. Black point
is the same function for shadows. I don't even know just what the next
control is most commonly called, but it is the same as the central
slider on the Levels control in PS. It sets the brightness that will be
in the middle, with all others spread or compressed fill the brightness
range on either side. Finally, there is often a setting or settings for
the curve which determines how much highlight and shadow brightness
values towards the end of the histogram are compressed in order to allow
those in the center to spread out, increasing contrast in the most
visually important part of the image.
For the problem you raise, the key settings are, White Point and Black
Point. Other things can be done at this stage, but also can be done in
post processing. If your converter has a histogram, just try the
controls until you find the ones that pull big stacks on the right down
and to the left until you barely get space between them and the end
point of the histogram. Exact detail depend on how the app works and
whether you have RGB or only an averaged histogram. That will set the
White Point to recover all the highlight detail that can be recovered.
If concerned about the shadow detail, do the same thing for the other end.
> http://thattimeoflife.smugmug.com/photos/72560784-M.jpg
>
> which I tweaked to bring the old couple out of the shadow, but by doing
> so blew out the sky.
>
You think you lost much more than you did. There is a great deal of info
there that we aren't seeing, it's just mis-distributed in the histogram.
I've gone a little overboard, to make a point, and left the mountains a
little funny colored, but just want to show how much more info is hiding
there. <http://www.moosemystic.net/Gallery/Others/Street.htm> Don't
just look at the mountains, look at the sidewalk in the lower left and
right, where detail and texture that was lost in highlights and shadows
reappears. And of course, the old couple are much more visible; I almost
put a spotlight on them and added some contrast so the detail stands out.
So if there is that much additional brightness detail available in an 8
bit compressed JPEG, imagine how much may be locked up in the 14 bit RAW
file!
If you want to send me the RAW file, I'd be happy to see what I can find
in one of the converters I use to give you a measure of what's possible.
Moose
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