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In this exercise I am going to show you what happens to those dark and light halos when
we are tracing an image that contains gradual transitions.
I am still working inside the Sharp Shapes.PSD file that's found inside the 01howitworks
folder. I've got my Layer Comps palette open and I
am going to switch- right now we are looking at the Standard Layer Comp-
I am going to switch down to the Gradients Layer Comp, this one right here.
So this is an alternate view of the image. It still contains the texture pattern but
instead of having a dark serpentine line set against a light background, we've got a gradient,
a dark to light gradient serpentine line set against
a light to dark gradient background. So we've got some opposite gradients going
on right here. That will allow us to see what happens to
those halos as I was saying, when we have gradual transitions. And you can see that.
Let's go ahead and zoom in on this image so we can really take it in close and personal
once again, so it translates to the video, and I am going to switch over here to Sharp
grads, this guy right here, this Layer Comp. And notice that we Now toward the top of the
image, notice that I am looking at the top region of the
image where the serpentine line is dark and the background is light, and we have a pretty
familiar pattern of halos here. We have dark halos around the
outside of the circles for example and light halos around the inside of those circles.
As I pan down, the farther that I pan down and the closer that we get to this region
where the gradients are pretty similar to each other, where we just have a bunch
of midtones going on. Notice that the edges, those halos, drop out.
So the halos actually get thinner and thinner and decline here almost like calligraphic
brush strokes, this one is happening here, its almost like
lading up off the pressure of a stylus, for example.
So that the dark edge is just disappearing, the dark halo is just disappearing.
And then it switches places. Then we start seeing a light halo emerging as the gradient
serpentine line becomes lighter than its background. So what was formally a dark halo transitions
to a light halo and what was formally, in this case up here, a light halo
on the outside transitions very slowly to a dark halo down toward the bottom and so
they gradually and automatically switch places. So Photoshop is intelligent enough not only
to the detect the edges inside the image and increase the contrast of those edges,
but also to trace the light halos, always on the light side of the edge and the dark
halo along the dark side of the edge, and the lightness
or darkness of those halos is commensurate with the degree of contrast.
So down here toward the bottom of the image where we have the highest degree of contrast
between the white serpentine line and the dark background, we have very nearly
a white halo on the inside and that black halo on the outside, and those halos become
less and less defined as the natural contrast between
the edges grows less defined as well, so that you can see that those halos just
start becoming not only more tapering but they also start growing darker,
the light halo grows darker and the dark halo grows lighter as well.
So there we have it to look at sharpened edges inside of a gradually transitioning image.
In the next exercise, I am going to show you the effects of combining sharpening with noise
reduction inside Photoshop.