How-to: Sharpening with edge masks

[MikaG]

Sharpening with an edge mask

 

1. This is a portrait after RAW conversion with standard sharpening applied to eliminate anti-aliasing from the sensor. The image is sharp, but not tack sharp. I will improve on this by using a sharpen filter in Affinity Photo. The problem is, that the effect is applied globally to the entire photo. Smooth gradients, like the skin will be affected also and in most cases this is not desireable. Therefore, I will show you a way to create an edge mask, which allows to only sharpen the edges and leave the gradient portions of an image intact.

[MikaG]

2. Duplicate the Background layer (Cmd+J) and apply the Detect Edges filter, so the copied layer will look like this.

[MikaG]

3. To turn this layer into a pure black and white image, create a new adjustment layer by pressing Cmd + U, which will add a HSL Adjustment layer. Take the Saturation Shift slider all the way down to -100%. Now you have a decent black and white edge layer where the edges are represented in white and the smooth gradients are “represented” in black. But we will improve on this in the next steps. Right now the edges are still too filigrane.

[MikaG]

4. By applying another adjustment layer, the contrast between blacks and whites are pushed even further. Press Cmd + L to create a Levels Adjustment layer and set the Black Level slider to around 5-10% and the White Level slider to around 40-50% as you see fit. The blacks are even more pronounced now, as are the whites.

[MikaG]

 5. Next select both adjustment layers and the b/w edge layer by Shift + click and press Cmd + Shift + E (or choose Merge Selected form the layers menu), so we can apply some more filters to the flattened edge layer.

[MikaG]

6. With this image I did no skin retouching whatsoever in the first place. Therefore all skin blemishes, spots and imperfections show perfectly in the mask. To reduce these press Cmd + 1 to zoom in to 100%, pick the brush tool and set the opacity to around 50%. Set the Blend Mode to Overlay and make sure black is your foreground color. With the Blend Mode set to Opacity, the dark pixels will be affected a lot more than the bright ones. To show the difference I painted the left portion of the face with the Overlay brush and let the right portion unaltered. If you already cleaned up the skin beforehand, this step is not necessary. But for the sake of demonstration of the cool Overlay feature of the brush, I cleaned up the mask a little. 

[MikaG]

7. Now it’s time to apply some more filters to expand and smooth out the masked portions of the image some more. First I apply the Maximum Blur… filter and set the radius to around 1 pixel. Activate the circular check box, to get smoother results. Now the boundaries expanded a little and the sharpening affect will eventually come through even more.

[MikaG]

8. With the help of the Median Blur… filter, adjacent pixels are evened out a little. Set the radius slightly above 2 pixels. I chose 2,1 in this case. As a rule of thumb, you generally want to set the radius to the double amount of the previously applied Maximum filter.

[MikaG]

9. The last filter that is going to be applied is good’ole Gaussian Blur. Once again, the double amount of radius of the Maximum filter is a good value. In my case I chose 2 pixels.

[MikaG]

10. This is the final version of the sharpening edge mask. Now it has to be applied to a sharpening filter to unfold its magic. Add a Unsharp Mask Live Filter and reorder the mask layer above the Unsharp Mask filter layer.

[MikaG]

 11. Activate the mask layer and choose Rasterise To Mask from the layer menu. Suddenly you can already see which portions of the image will be unaffected by the mask, i.e. sharpened. 

[MikaG]

12. Pull down the mask layer onto the Unsharp Mask layer icon to put the mask in place. Now double-click on the Unsharp Mask layer icon to adjust the sharpen values. Pull up the radius to the desired amount of sharpening. I set the radius to 2,1 pixels.

[MikaG]

Voilà! Details in the image are tack sharp right now and all the skin pretty much is untouched by the sharpen filter. Check out the before and after and readjust the sharpening sliders if you wish.

 

This procedure is applied quickly even if it has several steps. Once the function of Actions is added to Affinity Photo it will become a task even faster. To me it is absolutely worth the extra 60 seconds to get even better results with edge masking the sharpening effect. I have set custom keyboard shortcuts for most of the filters, so this speeds up its usage.

 

This method is totally influenced by Deke McClelland, who is one of the Photoshop Gurus and all the credits belong to him. After some trial and error I was able to translate his method to Affinity Photo and I hope to help some of you to achieve better results with sharpening techniques. Same rules apply to landscape photographs, architecture, still life… you name it. Play with the radius’ values depending on your sensor size and desired ‘focus’ of the sharpening effect.

 

Enjoy!

[bumz]

Very Nice. Good work.

[Madame]

Thank you. Saved this for later! :)

[anon1]

Nice and easy explanation, I'd personally prefer an threshold preview in the USM dialog to get close to the same effect and then simple mask out the remaining special areas (some skin regions).... Seems more flexible to me and hopefully we'll get it soon.

 

But your approach is certainly more precise (for those who have the experience)

[MikaG]

You kind of get a threshold preview when using the high pass filter. It affects mostly the edges in an image and leaves gradient portions untouched. I prefer high pass sharpening with people portraits almost all the time. USM serves better with lots of tiny details in an image. I only chose USM in my example, because it saved some additional steps like selecting blend modes like Overlay or Soft Light with high pass sharpen.

[anon1]

Yes you can certainly do so but it gives you not as much control (or costs more time to create the mask separately)

 

I'd argue that USM is even more useful at bigger structures because you can mask out the smaller ones.

 

For small structures a normal HP does the job.

[MikaG]

I know, it's a crutch. But you might get that threshold preview by changing temporarily the filter's blend mode to Difference.

 

I duplicated the layer, applied a USM live filter and set the blend mode to Difference. Difference will show you a preview of altered pixels compared to the layer below. You get an idea of how much pixels are affected by the USM filter. Of course you have to change back to Normal blend mode, to actually see the amount of sharpening you have applied. As I said, it's a crutch, but maybe worth trying...

[anon1]

At first I thought this could be great but trying it out I´m seeing that it does´t quite cut it yet cause it´s just way to unresponsive. Small changes are not reflected in the difference blend mode.

A sharpening effect I can already see in the picture (with USM set to normal) is not displayed in the difference blend mode. And if I´d adjust according to the difference blend mode - the picture is way over sharpened. 

 

So I´d still need the alt + drag unsharp mask preview that seems to feature some sort of gain.

[MikaG]

I haven't figured this out enough yet and maybe I got you wrong. But with Difference you can only estimate the radius of pixels that are affected by the threshold settings. It can't give a reliable preview of the strengh of USM. In my 12 megapixel example I can see faint changes in the Difference "preview" when I adjust the Radius value to 1% and it becomes even more obvious at the Radius of 2. Factor and Threshold I left untouched. Just make sure to view zoomed to 100% to get a representative pixel by pixel view on your display.

 

I agree, it would be great to have a more precise preview of each of the settings just by holding the Alt key, like Adobe Camera Raw does. But at the end of the day I'm fine with this method because I use edge masks anyway to protect from unwanted sharpening.

[MikaG]

As I dug deeper into AP - well, the help file obviously really helps - I finally got a grip on the Channels panel. Using channels makes life a lot easier, where masking is concerned. So, I decided to give a little update on my workflow. I’m still learning how AP works, so tweaking methods here and there happens a lot to me at the moment. Let’s get started with edge masking 2.0.

 

1. I chose the green channel, which provides the most details and right clicked on Pixel Green to choose Create Grayscale Layer which adds a new black and white layer in the layers palette.

[MikaG]

2. By pressing Cmd + I the grayscale layer is inverted and applying the Detect Edges filter reveals a base mask.

[MikaG]

3. Cmd + L adds a Levels adjustment layer. I applied roughly the same settings, as I did in my first tutorial. Now a really cool feature comes into play. In the Levels dialog box choose the Merge button in the upper right corner (actually rather centric, to be more precisely) and the Levels adjustment layer will be automatically merged/applied to the mask layer underneath. Another way to do this would be to make the Levels adjustment layer active in the layers palette and press Cmd + E, which also merges the adjustment layer down to the next pixel layer below, which happens to be the mask layer in this case. HINT: This method works with any adjustment layer.

 

From this point on all the afore mentioned methods still apply to create the edge mask and I won”t repeat these here. Just look into my first tutorial and continue with number 6 from here on.