As some (many?) of us who are lurkers and new to digital photography, I
would very much appreciate any comments the more experienced and regular
posters could add describing any post editing alterations they make to
the original image before they post them here.
I am playing with brightness, contrast and histograms, and am interested
in what you are looking to change and why.
For example, what exactly does sharpening do to improve an image?

john smith > wrote in news:4692f081$0$4672
:

> As some (many?) of us who are lurkers and new to digital photography, I
> would very much appreciate any comments the more experienced and regular
> posters could add describing any post editing alterations they make to
> the original image before they post them here.
> I am playing with brightness, contrast and histograms, and am interested
> in what you are looking to change and why.
> For example, what exactly does sharpening do to improve an image?


Okay, I do a lot of photo editing, you just don't see my stuff here
because I have few opportunities to shoot aircraft ;-)

First off, sharpness and contrast work better when your image is at
the "final" size - resize it for posting before messing around with
sharpness.

Sharpening is simply an increase in contrast in specific areas - how
specific is usually up to the user, but it depends on the editing program
you use. Do it after contrast adjustments (and contrast adjustments work
better in direct conjunction with brightness adjustments - usually you fare
better by increasing contrast about half as much as you increase
brightness).

Softness, at the pixel level, is actually a gradual transition
between one color (say, the black of the aircraft) and another (the blue of
the sky). If the transition is abrupt, little gradation between the colors,
that's what we see as a sharp edge, or good focus. So the editing programs
simply increase the contrast in areas where there is already a distinct
transition. In an area where the pixels might go from black, to dark grey,
medium grey, grey blue, bluish grey, dull blue, to bright blue, sharpening
may simply "round off" the transitional tones a bit to make the transition
from black, to bluish grey, to bright blue. More abrupt, and "sharper."

It can be overdone very easily, and this can create halos around
edges as the program overcompensates - that's too much, and makes an image
look too altered. I find that the best way to judge sharpening (or unsharp
mask, if you use a higher-end editing program) is to view the image at 200%
finished size, and watch an area of high contrast. When the halos appear,
back it off a bit.

Histograms can be useful, but only if you know what they represent. I
find that "curves" (if your program has that option) works better in that
you can selectively alter the levels easily - for instance, bringing out
the yellow in the midtones without altering either the highlights or
shadows. And it helps to be able to work in individual color channels (Red,
Green, Blue) rather than all at once. I have seen very few digital captures
that did not benefit from a color tweak, and most often, a decrease in
blue, which is a subsequent increase in yellow, because they're
complementary colors. Know your color wheel ;-)

Another little trick - pics in shade or overcast almost always have a
different color cast to them than bright sunlight, so brightening them also
requires a shift in color - more yellow, and a tad more red. And bright
sunlight is higher contrast, so a boost in contrast as well. Boom, you now
disguised the fact that the skies were not cooperating with you that day
;-)

Changes should be exceedingly subtle. It's very easy to
overcompensate when you're staring at the monitor. Look away for a minute
or come back to it a little later - you may see you overdid it.

And always save the original unaltered!

That's a start, but photo editing is a complicated process, so don't
hesitate to poke around on the web for tips, and spend some time learning.
Good luck!


- Al.

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