By: ledirlo
I'll say
it again: luminosity is the key to making good pictures; for those who
don't know , PHOTOgraphy means "light-print".Photo means light
(photon), when your eyes see an object , it doesn't see the object but
the light it reflects, absorbs, and/or emits.The intensity of light ,
it's tint, falloff , difuse map are what make your brain recognize an
object.Therefore, everything you do when you retouch a photo is to alter
the caracteristics of its light; a good , simple example is when you enhance
a landscape : you'll use curves, hue, etc, that all are commands that
alter the luminosity.Since 99% of you work on RGB monitors, photo retouching
consists in altering the value of each red, green and blue pixel in a
picture, modyfying the light it emits.
I just wrote this part because most people don't think of that and therefore
dont understand the way photoshop works, and wonder why I emphasize so
much on luminosity.Now I'll share some luminosity correction tips so you
can practice :
1: bad exposition
You just shot a pic , and the fact is that the exposition is bad: some
parts are visible, some are too dark.uneven luminosity.Here's a pic of
my nephew Lucas:
O bviously
the background on the left is too dark, so let's try this :
D uplicate the layer, (ctrl+j), invert the luminosity of the duplicate (ctrl+i),
put it in soft light mode, and give it a 9.0 gaussian blur:hooray the dark
part is now visible !
The problem is that it also altered the luminosity of the kid, therefore
just duplicate the soft light layer for safety, turn it off, and erase the
part of the visible one that overlaps Lucas with a large soft brush to get
rid of the luminosity settings the layer contains , and so you restore his
original luminosity
You can
see the shape of the layer in the layer palette: that's a way to correct
bad exposition , and even a pic's luminosity in a non destructive way.
2: Low contrast
If you shoot a pic and it has a low contrast, it means that his alpha channel,
or luminosity values are too modrate, low, even; in other words, the black
point and light point are not visible enough: I lowered the contrast on
the pic of Lucas to make an example
You have
two very good ways to fix it:
A: create a luminosity map:
Duplicate the layer, desaturate it (ctrl+shift+U), put it in luminosity
mode, and press ctrl+L
You can
fix the saturation by adding a little, and it's done!
Just
compare with pic 4 to see if you like it.
B:Jerry's
trick:
Jerry717
taught me and a few others that were on the discussion board this trick;
it's a very good example as it is efficient, easy, and practicing it will
make you understand the whole luminosity thing.
Take pic#4, create a curves adjustment layer over it; double click the eyedropper
on the right
And fill
in the rgb values with "250" : this prevents the picture to contain
a white point that would contain extreme, non printable color values.Press
enter, and , again with the same eyedropper, click on the bright part of
Lucas' t-shirt.
Now double click on the left eyedropper (set black point), and enter "3"
as rgb values for r, g, and b.press enter and click in the darkest zone
in the left side upper part of the pic .
Now do the same with the center eyedropper (set gray point), enter "128"
as rgb values: this makes your pic have the right, neutral color values.then
click the eyedropper where the arrow points at in pic 8
This
sets the gray point of the picture , and makes it get rid of the opposite
color that it contains.Try it everywhere on the pic to understand what I
mean.
Now just press enter to get out of the curves layer, duplicate the layer
and do this :put the adjustment layer in luminosity mode, duplicate it,
and put the copy in color mode.This lets you tweak each different settings
aprt from the others.Otherwise if you like the original result, just put
your adjustment layer in normal mode...the result I have is this one
The great thing about jerry's trick is that it also prepares the pic for
printing, since it implies good black point and light point values, both
for the eye and the printer.Thank you Jerry !!!!
Photoshop
CS added a "shadow/highlight" command that basically does the
same, but it doesn't explain you how it works....I prefer the old way.
You could
have tried the second trick "luminosity layer" with an overlay
layer instead.....just try some more, using opposite values, deasturated
layers so you understand precisely how this works.
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