OV3: Sharpening with Unsharp Mask

OV3: Sharpening with Unsharp Mask
Final edit with Unsharp Mask
OV3: Sharpening with Unsharp Mask, Intermediate edit
Intermediate edit with Art Filter, Contrast, and Saturation

What is Unsharp Mask

Contrary to what you were thinking when you first came across the term, an 'unsharp mask' is actually a tool used to sharpen an image.

It is most probably the most common type of sharpening and is available as well on Olympus Viewer 3 (OV3) for sharpening of both JPEG and *.orf RAW image files.

OV3: Sharpening with Unsharp Mask, RAW file
*.orf RAW image file as uploaded
Technically, the process works by utilizing a slightly blurred version of the original image which is then subtracted from the original to detect the presence of edges. Contrast is then selectively increased along these edges using this mask, leaving behind a sharper final image.

The three images above (shown in reverse) shows the 3-stage process which I adapted in my workflow. Briefly, Stage 1 is to get the image uploaded and opened in RAW Development Mode on OV3, Stage 2 covers all edit necessary, including Crop, before applying the Unsharp Mask in Stage 3, which may take a while due to the inherent slowness of OV3.

Olympus Viewer 3 RAW 1 Basic Edit tools

When to use Unsharp Mask

Sharpening should also be the last step of the editing process. Do this after you have completed all other functions which may include Art Filter application, Exposure Compensation, White Balance setting, Highlight & Shadow Control, Contrast, Saturation, Crop and Tone Control adjustments.

It is also pertinent that you do the Unsharp Mask adjustments in 1:1 view or at least 50% magnification. Doing it in other magnification may end up with images having anti-aliasing weirdness.

In RAW Development Mode on OV3, I do this by simply following the function/feature list on each of the three menu sets displayed - RAW 1 (Basic 1), RAW 2 (Basic 2), and Edit. Go down the list of the menu items and pick the one you want to use, before moving to the next menu block. You will end up in the Edit block where Unsharp Mask is the last item listed.

Olympus Viewer 3 Image Edit tools

Function Variables

Digital unsharp masking is typically controlled by three settings - Amount, Radius, and Threshold. In OV3 they are displayed as slider controls on the function menu:
Olympus Viewer 3 Unsharp Mask tool
  • Amount - Controls how much darker and how much lighter the edge borders become. The value is adjustable between 0 to +500, listed as a percentage.
  • Radius - Controls the size of the edges to be enhanced or how wide the edge rims become. A small radius enhances smaller-scale detail while high radius values can cause halos at edges. The value is adjustable between 0 to +250 pixels.
  • Threshold - Controls the minimum brightness change that will be sharpened or how far apart adjacent tonal values have to be before the filter does anything. The value is adjustable between 0 to +100 pixels.

*.orf RAW Image file
*.orf RAW image file as uploaded

Worked example

Let us go through a worked example here, another image of one of my garden plants. the mage was in *.orf RAW file, uploaded and opened in RAW Development Mode on OV3.

Intermediate edit with Art Filter, Contrast, and Saturation
Intermediate edit with Art Filter, Contrast, and Saturation
Stage 2 development was done with the following adjustments:
  • Art Filter: Pop Art
  • Contrast: +2
  • Saturation: +2

And for Unsharp Mask, work was done at 1:1 with the following function values.
Olympus Viewer 3 RAW Development Window at 1:1 zoom
Unsharp Mask edit at 1:1
  • Amount: 400%
  • Radius 4.0
  • Threshold: 15

The final image

OV3: Sharpening with Unsharp Mask Final image
Final edit with Unsharp Mask
Going forward
You may want to use my values here as a start to your own image sharpening process using the Unsharp Mask. Treat this as a start point, and you’ll want to push the values around until it looks right to you.

Try even starting with: Amount: 85%, Radius=1.0, and Threshold: 4, and see where you will get from there. These are figures quoted for an all-purpose sharpening I picked off the Internet.



Resource Links:
Unsharp Mask: How Do You Actually Use That Thing?
PSA: Say Farewell to Unsharp Mask When Sharpening Your Photos

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