today we're going to be looking at how sharpening works and specifically how
you can use this information with the Photoshop unsharp mask now I'm picking
the unsharp mask because it's quite simple to understand what's going on
let's start that by creating what we call a sharpening wedge now the way to
do this in Photoshop select the marquee tool we can then use that to draw out a
rectangle though this will form our sharpening wedge where to draw the wedge
we need a gradient now I've got mine set up to go from black through to white I'm
just going to click on one side of the marquee and drag across to the other
when I release that creates my gradient I'm now going to copy there and now I'm
going to paste that now that creates me a new layer in the layers window can
turn off the original and you can see the new layer
but I'm going to do now is select the move tool I'm going to use this to
transform the new layer that I've created by flipping it through 180
degrees I can now move that down and align it to the other gradient so I've
now got two gradients running in opposite directions that go right next
to each other know for a bit of theory about how sharpening actually works that
zoomend on the gradient over here on the left side you can see that we've got a
very dark area and a very white area which we going from black to white now
notice how easy it is to see the sharp edge between the two in the gradient now
let's move over towards the center of the gradients where they cross over here
the tones are very very similar and it's very difficult to see the difference
between the two it's this difference in contrast between two adjacent areas that
creates a sharpening effect if we want to make one gradient stand out more
against the other what we need to do is make me this edge here more like the
edge here in other words rather than being too similar gray tones we enhance
the edge and make one darker on one lighter this is what sharpening does
it's a contrast adjustment along an edge and I'll show you how that works in just
a moment with the unsharp mask now before I do this I just want to create
what we call a stamp layer and that will combine these two layers together this
means that I'm no sharp link one layer that has both of the gradients on it so
let's open the unsharp mask and have a look at it you'll find it in the filters
menu and then under the sharpened submenu
though straight away you can see we've got some enhancement going on along the
edge now this amount slider here is what controls Hosts strong that enhancement
is so for example at the moment we've got it at 1% so it's having virtually no
effect at all watch what happens in the areas here where the tones are very
similar gray as I move the slider up
as I increase the slider what we're starting to see is that an edge here is
being created and that edge is making gray appear grayer and light grey appear
lighter what determines whether a tone becomes lighter or darker is how near it
is to the mid-tone gray value of 128 so if something is lighter than a mid-tone
the contrast enhancement applied by the amount slider makes it lighter if it's
darker than a mid-tone then the contrast enhancement makes it darker and the
further I move this slider up to the right the more that contrast adjustment
is applied so that it becomes stronger and stronger and when you can see it
expects iment value it's affecting almost the entire length of this
gradient until you get to the mid tone here where there's no difference between
the two pixels so they both the same value but that's where it has no effect
no look at the width of this enture that's being created but the moment it's
were really easy to see now this is called a sharpening halo now a lot of
people talk about sharpening halos as if they're a problem and they're not a
sharpening halo is always produced if it wasn't produced you wouldn't get the
sharpening effect the problem comes if you make the sharpening angle out too
strong as we have done here the amount is at 500 so literally every edge is
going to be black and white and that's very easy to see when you look at an
image and you don't want that so typically you'd reduce the slider down
here to where it becomes less obvious now I'm going to leave it up at maximum
value from the moment and the reason is because I want to show you this other
slide the radius slider now the radius slider controls how wide an edge is
being created now at the moment it's 4 pixels if I push it up further to 45
pixels you can see a massive edge is being created if we move it down to
around 1 you can see that hardly any edge is being created
and if we combine the two together so that we've got not too strong a contrast
enhancement and a small radius what we see is that there's an hour distinct
edge between the two gradients but that's very hard to detect even though
unmagnified at 200% now the final slider that we've got here is threshold so
let's have a look we will strengthen this we'll make it wider so you can see
it and we'll push the amount up again so we've got a very distinct edge now as we
said before you can see that edge extending right the way along the
gradients until we get to the middle what determines whether or not Photoshop
detects an edge is the threshold so what the threshold is doing is its testing
adjacent pixels and it's trying to see how much of a difference there is
between the two and when we've got it down at zero basically it will enhance
any difference at all that it finds in pixel brightness if I move this now to
the right what we see is that the pixels have to have more of their difference
between their levels of brightness before the enhancement takes place and
that's why we're not seeing any sharpening in this central area now and
the further I move this slider over to the right the less effect it's having
notice that the effect now is in this left side of where the two gradients
cross and I can move that all the way out here to where there's literally no
effect and no sharpening between the two because there has to be a massive
difference between the adjacent pixels before they become sharpened if we pick
something like 60 pixels or what we're saying is that the difference between
the lightest and brightest areas has to be at least 60 difference on the tonal
scale and remember the tonal scale runs from 0 to 255 0 being black 255 being
white the radius slider now will can reduce that down so we'll move it back
down to a default of our own one which is usually good amount and if we move
that down to around 96% what we see here is an
enhancement of the two gradients in the sharpening wedge to make that edge stand
out so I'll apply that I'll go back to 100% and you can see that the two
gradients are a little sharper than they were before
we've enhanced this sharpness but we haven't made it so obvious that we
detect a problem well let's look now at applying what we've learned to this
image and we'll sharpen it using the unsharp mask now I've already created my
new layer for the sharp link and I'm going to zoom in to 100% on the
background I'm also going to look at this particular area so that I can
monitor it for sharpening now it's already quite sharp but we can probably
make it better using the mask I'm going to no take the unsharp mask filter and
apply it though the default settings that I've got and just the ones that I
was using earlier and I can change these to something that's more suitable for
this image so let's start by pushing up the sharp link to a higher amount if you
remember that this creates the sharpening effect by enhancing the edges
with greater contrast now as I've done that you can see an edge very faintly
starting to appear along the headland here and if I make that a little bit
wider using the radius slider you can see we've got a sharpening halo that's
quite ugly so let's pull that back down for a little bit down to about one tab
and we'll also make this sharpening radius a little bit narrow
that's about 1.7 and we'll move it down still further because I can detect the
edge a little bit too much so at 1.4 it doesn't look too bad and we can probably
get away with applying a little bit more sharpness
though the other thing that's happening is that we're sharpening with the
threshold at zero so that means everything is being sharpened where
Photoshop detects a difference between adjacent pixels and I don't really want
that because there's a lot of sort of the water from the long exposure here so
I'm just gonna move that up to something like 30 now what that's doing is it's
concentrating the sharpening onto the rocks where there's a greater tonal
difference between adjacent pixels and it also means that I can push the
sharpness up probably further still and the radius just a little bit more now I
still have to be careful because on this edge here there's probably quite a
difference between the sky and the rocks and it will still show an edge but let's
turn off the preview for the moment and I'm not sure if you can see it on the
video but actually it's made a reasonable
difference to the rocks in terms of the sharpening and I can probably drop the
threshold down a little bit further there now given that this is only the
unsharp mask and not the smart sharpen filter we don't have any controls that
we can use to get rid of the halo all we have to do is try to not make the hay
look too strong and that looks about right if we were using the smart sharpen
filter we had to have options there to fade the sharpening in the highlights
and the shadows so that we can control the halos better for now I'm happy with
the result let's click OK we can turn that off where we can see there is a
difference between the sharpening if I turn it on you can see that especially
in these areas where we've got the likens on the rocks I hope you find this
useful I'm Robin Whalley you've been watching the lenscraft I'll see you
next time for another video