Here's what I do:
00) Presumes a calibrated display system and Adobe Photoshop set up
to use color management as appropriate for best results.
0) RAW conversion is adjusted to set the white and black clipping
points and fix the overall histogram to maximize having data to
process. This is not necessarily the best looking color rendering.
All other steps can be done from any RGB file. [EMAIL PROTECTED] data
allows more processing overhead before roundoff errors start to
damage the image.
1) Add an Adjustment Layer using the Channel Mixer over the
background image data. Set the default values to R=20%, G=75%, B=5%,
bias=0%, "monochrome" checkbox on, name the layer "BW Conversion". (I
have an action that does this in one keystroke.)
2) Examining the image, adjust the Channel Mixer percentages of R, G
and B to provide the tonal differentiation and spectral response you
are trying to achieve ... This is the part that take some time and
practice to learn. If you are trying to separate skin tones in
tungsten light, you'll need different settings from when you're
trying to render foliage under the noonday sun. Etc.
3) Sometimes an image needs one mix of spectral response in one area
different from the others, other times the illumination level changes
color temperature and thereby a different spectral response is needed
for dark areas vs light areas, sometimes you need to handle noise in
some areas by selecting a different mix as well. You can stack
Adjustment Layers using the Curves tool *between* the background data
and the Channel Mixer layer and edit the curves in Red, Green and
Blue explicitly. Also remember that you can add masks to every layer,
mask an adjustment layer to constrain the effect to exactly what is
needed.
4) Once you have all the chroma translation done into data you can
work with, you add Curves adjustment layers and masks *above* the
Channel Mixer Adjustment Layer to control the grayscale tonalities.
This is where you apply the analog of burning and dodging under an
enlarger, or even changing the paper grade of a section of the image
with custom filtration, etc.
5) Save the .PSD file complete with layers ... that allows you to go
back and re-adjust any piece of the rendering process you might want
to at any time. The background data is completely unchanged.
6) When you reach a point of calling the image finished, flatten all
layers. The adjustments you've made are now all integrated with the
background data. I usually combine this with a colorspace conversion
to Grayscale Gamma 2.2 or 1.8, or sRGB for web presentation. Save As
to a new file ... you cannot go back to the RGB rendering from this
file, it's for output to printer and further processing work for web
presentation.
Other layered approaches include techniques like using HSV adjustment
layers to manipulate chroma translation to grayscale and can produce
results right on par with this, but I find the above to be easier for
me to work my head around and more selectively manipulable.
Godfrey
On Oct 31, 2005, at 4:39 AM, Adam Maas wrote:
Would you mind posting your workflow for this method? I'm using the
non-layer Channel Mixer method:
Open Channel Mixer
Set Monochrome
Set Red to +60
Set Green to +40
Tweak for basic tonality
Add contrast curve if necessary
and would rather like a quick into to a non-destructive method. My
experience with layers is sadly lacking, so I'm not sure where to
start when adapting this method to layers.
-Adam
