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This GIMP (GNU) tutorial demonstrates how to Sharpen Images. To work along, you are welcome to download the Photograph I am working with Here. Unzip the file and open the image onto GIMP’s workspace.
Duplicate Your Image
To preserve your original image, remember to Duplicate it. To Duplicate an image, from the top menu, choose Image then choose Duplicate - Ctrl then D. Now, close the original image and work on the Duplicated Image.
Understand Colour Models
Optimise And Save Images/Photographs
Which Sharpen Filter?
Individual photographs will always have unique out of focus problems; therefore, for personal results, experiment with different Sharpening options and discover a technique that works best for your image.
Applying a Sharpening Filter instantly breaths life and adds clarity to any photograph, and for this reason, the Sharpening Filters are arguably GIMP’s most useful Filters. Generally speaking, it’s considered good practise to complete any photographic manipulation - (or Resizing Conversion) by applying a Sharpening Filter to it afterwards.
GIMP’s Filters usually work well when mixed with each other; that is to say, when more than one Filter is applied to a photograph: however, when road-testing the Sharpening Filters, you’ll produce much better Sharpening conversions if you Undo (Ctrl then Z) a previous(or a current) Sharpening Filter before applying a different one.
The Sharpen Filter
The Sharpen Tool
The Unsharp Mask Command
Open your Start Image onto GIMP’s workspace - File then Open - Ctrl then O.
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History).
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down
GIMP has two Sharpening Filters and one Sharpening Tool. To apply a Sharpening Filter to an open photograph, from the top menu, choose Filters and then choose Enhance, and from the subsequent drop-down list, select a Sharpening filter that suits your photograph’s needs. Your two Filter choices are Sharpen and Unsharp Mask.
The Sharpen Filter
From the Sharpen Filter’s dialogue box, left-click, and then drag the Sharpness slider to to a position that works best for your photograph’s needs, and then click OK.
The Unsharp Mask
The Unsharp Mask is named after a technique found in photography where a blurred and in-focus image (of the same subject) are combined to create a sharper image. When you blur an image, GIMP looks at all of the images pixels - takes their values, and then compares them to the values of the pixel. It then works out an average to create the new pixel value. The Unsharp Mask does the reverse, it looks at the value of the pixels around it and works out how it can subtract - so that it stands out more. Experiment with the Unsharp Mask Filter, and discover settings that work best for you.
Unsharp Mask’s Default Settings Example
The Sharpen Tool
From the left-side Toolbox, activate the Blur/Sharpen Tool.
And set the following Sharpen attributes into the left-side Options Bar.
Tip: Quickly Resize The Brush
You can quickly resize the Blur/Sharpen Brush by holding down your Keyboard’s Windows Key, and then tapping either the left or the right Square Bracket Key.
Now, left-click to apply the Sharpen Tool’s Brush to small photographic areas.
Sharpen Tool Notes
The Sharpen Tool is ideal for sharpening areas of images, rather than the whole image. Applying this Tool focuses soft edges, so increasing clarity. However, be careful, as over sharpening leaves a somewhat grainy look - as illustrated below. To avoid over sharpening, set a low Rate value in the Options Bar.
It’s best to make the sharpening subtle and increase it as necessary by repeatedly applying the Sharpening Tool over an area, building up sharpness, slowly.
Now you are familiar with GIMP’s Sharpening Filters and Tool, you’ll be able to get the very best from your digital photographs: spend a little time practising, and discover how Sharpening can dramatically improve your images’ clarity and focus.
Wendi E. M. Scarth. Top of Page.