a lot of people make an easy to avoid mistake when sharpening their photography I'm going to sharpen
this image in Affinity photo so you can see the problem I've already processed the image and when
magnified 100 we can see a lot of detail I'll now add a new life filter layer from the layer menu
to sharpen it in the sharpened group I can choose to apply the unsharp mask filter which is probably
the most popular sharpening filter when I do that you can see the new unsharp mask live filter on
top of the other layer the way this Filter Works is by comparing the tonal values between pixels
to identify edges we can then use the factor slider in the dialog to increase the contrast
between those pixels this makes the edges in the image Stand Out further and creates a sharpening
effect currently the factor slider isn't having any effect on the image because the radius is
set to zero what the radio slider controls is how wide an area the factor slider is affecting when
the radius is at zero it means the factor slider doesn't affect anything in the image if we look
at the distant Hills on the horizon and set a high radius and Factor you can see them being sharpened
this effect is called a sharpening Halo because what we see is an obvious bright area around
the edges of objects if we look at the area at 300 percent you can see what's happening
edges now have a dark and light area around them where the contrast adjustment is being applied we
can see this clearly because the radius slider is too wide and the factor slider is too high
reducing both of these can help to limit the sharpening Halo problem to prevent it becoming
obvious in the image sharpening Halos is something that we want to avoid and often indicate poor
editing now let's examine the lichens on the rock we can see that these are being sharpened
but perhaps not as much as they need to be to give them a 3d effect but when I increase the
sharpening I begin to notice the Halos again also if we check the grass in the foreground
some of the lighter areas appear overly sharp but at the same time some of the darker grasses look
fine it's easy to draw the conclusion from this that some areas of the image need more sharpening
than the others this is true but probably not in the way that you might be imagining
our problem is that we're applying too much sharpening to the areas that are already quite
light and it's turning them white that's what we saw on the horizon Where It produced the
Halo with a dark and light edge but when we look at the areas that appear to benefit from
stronger sharpening we see that they have a lot of mid-tones so what we really need is a way to apply
more sharpening to the image mid-tones and less to the shadows and highlights functionally there is a
way to do this using the blend options dialog in Affinity photo you can use this to control which
pixels in the image are affected by the adjustment based on their luminosity in other words how light
or dark they are to access the blend options first select the layer to control in the layer
Studio panel you can then click this small Cog icon at the top right of the layers panel what
we see now are two grids the one on the left is the source layer ranges and controls how
the sharpening layer affects the layers below it the grid is like a graph with the horizontal
axis representing possible tones in the image on the left is black and on the right is white
then at the side we have a value scale running from zero at the bottom to one hundred percent
at the top the line that we see running along the top of the grid is used to control how the layer
is affecting the image because the line is up at 100 value the layer is affecting the image with
one hundred percent now suppose we don't want our sharpening to affect the dark tones in the image
all we need to do is drag the black point on the left of the line down to the bottom now the line
is at zero percent value for black and 100 for white if we look at the mid value of gray in the
center of the grid we can see that it is set to 50 percent going back to what we said earlier we want
the sharpening to be applied to the mid tones but we don't want it to be applied to the darkest and
lightest tones to do that we move both the black and white points down to the bottom of the grid
and a value of zero percent we can then click and drag the center point up to the top and a value of
100 percent in fact what we really want is for the sharpening to be applied at full strength to the
entire mid-tone range and not just one point to do that we just need to add an extra point now we can
see the line is at the top for the mid tones but at the bottom for the darkest and lightest pixels
it's then possible to apply stronger sharpening without producing exaggerated sharpening halos
in the brightest and darkest areas now I know what you're probably thinking I've picked a
certain image to use for this video because it only works in special situations that isn't true
this technique works when sharpening any image because it avoids the mistake that most people
make which is to over sharpen the highlights and the Shadows but there's a lot more to using the
blend options dialogue than sharpening as I demonstrate in this video it's a great one
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