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Advanced sharpening with high pass using Apply Image


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I was going through various videos and articles on sharpening to understand it better.
One unwanted by-product is halos and there are various ways to remove it. Also, some
methods produce harsher areas in the brighter part. Found this video

 

 


interesting but it is for photoshop. I was wondering how to use it for AP. Only two points are to be mapped for affinity photo.
One is Surface blur and another is the Offset and Scale inside the PS Apply-Image dialog box.
For the surface blur, AP equivalent is Bilateral blur. For the other two, I did some trials and found as below.

In the video, there are two layers - High and Low. High layer is the target and Low layer is the source
as far as Apply image command is concerned. Then offset is 128 and scale is 2.
To get the same result in AP Apply Image command under Filters, we have to first select the High layer.
Then from filters, click Apply image. Then click+drag the Low layer and bring it into the apply image
dialog box. Now the equations box will get enabled. click it. Now enter to make like this .
DR=((DR-SR)/2)+0.5
DG=((DG-SG)/2)+0.5
DB=((DB-SB)/2)+0.5
Blend mode is NORMAL and not SUBTRACT.
Click Apply.
Now the result is same as that of PS, in the video.
The bracketed step shown in the next line which de-saturates is not a must I think but some videos recommend it.
(To the High layer, clip a HSL adjustment layer . In the HSL, move the saturation slider to extreme left (-100%). This is to remove color info
from the High layer. Merge the HSL layer with the High layer.)

From here, the video can be followed as it is same for AP or PS.

Incidentally, the above method is also used for frequency separation in many PS videos with the difference
of using gaussian blur instead of surface blur. Here also, the same equations can be applied. (De-saturation step is never done in frequency separation). Since there is a frequency separation filter available in  AP , manual method is not required unless one is
experimenting or learning.

I tried various advanced sharpening methods and found this PS video to produce very good results.
With the above workaround, the video can be applied to AP also.

If any expert or others on AP equations note any mistakes in the above formula or method, please step in and
correct because I do not want anyone to follow wrong methods as I am not an expert in advanced
methods of AP.

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The above text is edited today. There was a monochrome conversion(de-saturation) of the High layer using vibrance adjustment layer after
Apply image. This step was giving color cast. It is now done with an HSL adj layer with its saturation slider set to -100%. B&W adj layer can also be used.
Now there is no color cast.

After viewing different videos on advanced sharpening , I note that some of them de-saturates and some don't. Technically, de-saturation is preferred I think because it then uses only the luminosity value.

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The images below shows that the advanced method is really good, does not smudge away details and also does not
make highlights overly bright. I have also not used the HSL de-saturation step in the trial below.

 

This is original 100% magnification screenshot without editing.

original.jpg.088a907ed24000d77da905fa3612d52a.jpg

 

This is the advanced highpass method described in the first thread. In one image I did about 7 radius and 14 threshold
for the blur. In another image, it was 14 radius and 14 threshold. So the second image has more sharpening. A mask was used
to bring only the face from the 2nd image and not the hair. Note that compared to the USM sharpened last image, there is
no smudging on the face and the small white highlight below the left nostril is not harsh. USM sharpened image is harsher.

highpass.jpg

 

USM sharpened image

usm.jpg

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Here is another screen shot of 100% or 1:1 pixel on screen. The left image is original and right image is sharpened with above method.
Before sharpening , mild colour and contrast improvement was done in LAB mode. Sharpening done last, in RGB. The background
is masked out from the sharpened layer using a mask that is white for the bird. So only the bird appears sharpened. So no unwanted
noise or grains in the background green unfocused area. D7000/ sigma 150-600 C, 1/320 sec / 1000 ISO, 600mm , handheld.

 

LEFT ORG RIGHT SHARPENED 100 PER MAG.jpg

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