The
easiest method for using a photograph is to run Image > Adjust >
Threshold. Maybe clean it up with some airbrushing, smooth out some of
the rough edges, and you're good to go.
But Threshold is so harsh, isn't it? I usually opt for Image > Adjust
> Levels (ctrl + l) as it offers a more control. It's also a good idea
to convert a colour photo to greyscale before using Levels. Since brushes
are greyscale, converting to grey first will give a better visual indication
of how your custom brush will look.
That brings me to converting a colour photo to greyscale. Things are
going to get a bit tricky here, and I'm going to start talking about Adjustment
Layers. Ready?
This is a cool little trick passed down to me by a photographer buddy
of mine. This is a great way of converting a colour photograph to greyscale.
Open your photo in PS. Add an HSV Adjustment Layer and bring Saturation
all the way down. Tada! Instant greyscale, but some of the contrast between
colours can be lost. To fix it, use a Curves Adjustment Layer *between*
the photo and the HSV Adjustment Layer. Not only does the Curves give
you control over the contrast, but you can tweak the contrast in the seperate
RGB (or CMYK) channels. Did you catch that?
Okay, start with a photo of some clouds. Nice white clouds and a nice
blue sky. When such a photo is converted to greyscale, chances are pretty
good that there isn't enough contrast. You could adjust the contrast after
the fact, but a great deal of control is lost in doing so. Enter Curves.
With Curves, you can tweak the contrast seperately in the Green and Red
channels, thus pumping up the contrast for the greyscale. Woo!
Works
great as a stand-alone technique. Can really work wonders when converting
flesh tones to greyscale. And, because of using Adjustment Layers, you
can paint areas out if your adjustment layers that are too harsh for some
areas of the canvas.
What does this have to do with making custom brushes from a photo? Well,
brushes are greyscale, and having this kind of control over converting
colour to greyscale is a *major* bonus.
Ah, but chances are you don't want to turn a whole photo into a brush
-- just select bits and pieces of it. Right? Thought so. Enter Colour
Dodge. Bah! Rather than explain this in it's entirety, I'll just run you
through setting this up.
Grab a photo. Add your Curves Adjustment Layer and HSV Adjustment Layer
in the proper order (don't forget to bring Saturation down all the way
down in the HSV Layer). On top of all this, add a new layer, fill with
white, and set the Blending Mode to Colour Dodge.
At this point, everything should look white. Wah? Well, the Colour Dodge
Layer is for painting on with black. I use Airbrush set to about 25%.
If you want a part to show, paint with black. If you want to hide something
that you don't like, paint with white. It's easy and pretty neat to be
able to paint a new custom brush in this manner. It's kind of like sculpting.
I usually add a Levels Adjustment Layer to top off all of this. Woah,
even more control (normally I would use another Curves, but Levels is
enough control for me at this point). Sometimes I'll run a slight Gauss
on the photo if the edges are too harsh.
In the end, it looks a little something like this:
5)
Adjustment Layer > Levels. Tweak to taste.
4) Layer filled with white and set to Colour Dodge -- this is the layer
that is painted on (Airbrush ~25%).
3) Adjustment Layer > HSV with Saturation all the way down.
2) Adjustment Layer > Curves. Tweak to taste, in seperate channels
if necessary.
1) Photo, sometimes with a light Gauss.
I have an Action that I recorded that sets all this up for me for when
I'm in the mood to play around. Pretty damn spiffy, and a quick way to
make custom brushes. With all of the tweakability, quite a few brushes
can be made from the same photo. The really cool thing is that Edit >
Define Brush works on Merged -- gotta love that.
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