Masked Sharpen Procedure in Photoshop
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I started a new forum post rather than responding to BCrose and GiacomoD in a post "Bored in BC" where I mentioned using a sharpening mask to eliminate the harsh lines that appear due to sharpening already sharp edges. This probably belongs in another section, so if Donald decides to move it or eliminate it, I hope he will mention that in a private message to those two individuals.
This description is used to prevent over-sharpening existing edges while still significantly sharpening non-edge portions of an image.
Before getting started, you should know there is a nice tutorial on sharpening on Cambridge In Coulour's web site at https://www.cambridgeincolour.com/tu...sharpening.htm
I used Photoshop CS6 for this procedure.
The first image is the original pre-sharpened image.
Step 1: Select the Blue Channel only by turning off Red and Green Channels.
Step 2: Right click the Blue Channel and choose Duplicate Channel. Accept the default name and click OK.
Step 3: Turn on the new Blue Copy channel (click the eye) and turn off the normal Blue channel (click the eye). The image will appear black and white.
Step 4: From the main menu, choose Filter > Stylize > Find Edges. You will now see an image where all the edges are various shades of black. The sharpest edges will be the darkest, and the less prominent edges will have shades of gray.
Notes:
A.) In the mask we are creating, the lighter the area, the more sharpening will take place and the darker areas will be less sharpened.
B.) If there are areas that you do not want sharpened, use the paint brush to paint black over those areas. For example, sometimes sharpening the background can be distracting and takes away from the main subject. You can paint the background area black to keep it less sharp while you sharpen areas of the main object.
C.) You can use a levels adjustment to darken or lighten the areas. Use keyboard Ctrl(Cmd) and 'L'. Another thing you can do is to make a pure black and white mask with no shades of gray by setting a threshold. From main menu, choose Image > Adjustments > Threshold
Step 5: From the main menu, choose Filter > Blur > Gaussian Blur. Set the radius to 2.0 pixels before clicking OK.
Step 6: Save this channel as a mask. Do this on the channels pane (window) by clicking the circular dots icon at the bottom. After clicking you will see the dashed lines all over the image.
Step 7: On the channels pane, turn on all the color layers (by clicking the eye to the left of RGB) and turn off the Blue Copy channel (by clicking eye). You will now see the selection on the colored image.
Step 8: Save this selection. From the main menu, choose Select > Save Selection. I name the saved selection Sharpen Mask.
Step 9: Next create a new layer with pixels. If the only layer in your project is the background layer, right-click it and choose Duplicate Layer. If you have layers above the background layer, or do not have a background layer, choose the top layer and then using the keyboard, hold down Ctrl(Cmd) + Shift + Alt(Option) and then press the 'E' key. I like to use smart layers, and to do this, right click the new layer and choose Convert to Smart Object.
Notes:
A.) If the selection disappeared off the screen, you can restore it from the main menu. Choose Select > Load Selection. When the dialog appears, click the Channel drop down and choose Sharpen Mask. You should again see the dashed lines all over the image.
Step 11: Expand the image to 100% and scroll to an area that you want to view during the sharpen process.
Step 12: Choose a sharpen option from the main menu. I prefer the smart sharpen option. From the main menu, choose Filter > Sharpen > Smart Sharpen.
Step 13: On the dialog that appears, choose the sharpen amount. I typically use between 80% and 120%. Choose the sharpen radius. I typically use between 1.3 and 2.6 pixels. Choose what you are sharpening, which will normally be Lens Blur. Then click OK.
Step 14: Deselect from the main menu by choosing Select > Deselect. Adjust image size on screen to your liking.
Here is a view of a section of the original unsharpened image.
Here is a view of the same section sharpened. Note that there is a light line around the top the church and the intersection of the land and sky. This is probably the result of some sharpening that I did in previous processing steps. It is less than what you would have seen if the mask were not used.
And here is the full image sharpened.
Here is my caveat. Results will vary depending on sharpening and noise levels in the original image and the settings and type of sharpening you choose. Use at your own risk! I recommend practicing this technique until you get a feeling for settings and images that work well for you.