Image sharpening is creating emphasis in texture bringing the viewers’ attention to what is the focus of the image. There are different methods and means of sharpening an image, some are creative, others are for correcting issues caused when images are captured or outputted. One question I was recently asked during a twitter chat
Yes even for beginners all images need some sharpening and once you start sharpening your images you will never go back.
Capture Creative and Output
One of the first steps in editing an image should be capture sharpening. When we take a picture, the picture goes through the lens and then is recorded onto a light sensitive material, be it film or digital. During the capture process the lens and the sensor soften the focus of the image. The reason for this is that cameras capture images on red green and blue information channels, in doing this it can create artifacts and random colored pixels as well as stepping. Camera manufacturers don’t want their cameras producing images with these defects so they apply a slight blurring to the image in camera, softening the image.
Capture sharpening allows you to correct this softening effect.
Output sharpening is similar to capture sharpening. Sharpening for output needs to be the last step before printing and applied after you have resized your image. How much you sharpen the image will depend on your image size and output medium and device. Output sharpening is used to compensate for the softening caused by some output devices. All images being printed need to be sharpened for output. When you print the ink falls on the paper and it becomes deformed, spreads and runs. This happens because of the absorption of the paper and the ink being used. From device to device this softening effect will be different so there is not one sharpening setting for all.
Images being projected would need a little less output sharpening and those being used for web would usually need none, if capture sharpening has been applied.
Creative sharping is a nice term to mean localized sharpening, unlike capture and output sharpening, creative sharpening is not made globally but applied selectively to an area using brushes, masks and gradients.
How does sharpening work?
Most sharpening software uses something called an unsharp mask. Sharpening with an unsharp mask works by creating contrast between light and dark pixels (lighting light pixels and darkening dark ones) emphasizing edges. Although the process creates an apparent sharpness, the computer though doesn’t know if two pixels next to each other are actually an edge or digital noise. This is why with most sharpening tools you are given three settings, Amount, Radius and Threshold. Amount controls the strength of the process, while Radius sets how far from the edge sharpening is applied and Threshold controls how many pixels need to be next to each other to define an edge.
For capture and output sharpening these global settings are fine and creating presets wouldn’t be a bad idea. Though when it comes to the actually editing of images, you will need to be sharpen for that specific image. With portraits you would really only want to sharpen the eyes and mouth while not sharpening the skin, whereas a landscape image with a lot of texture may need several elements sharpened at different strengths
Sharpening In Your Workflow
There is no one right or wrong method to sharpen an image; it comes down to personal preference and what software you use to edit your image. The first step capture sharpening is applied when first editing an image and after you have made adjustments to the midtone contrast (clarity). Creative sharpening can be applied after you have reduced image noise (so as not to sharpen noise). Output sharpening is the last step before printing. I will not apply this sharpening step when I save the original image file. I will sharpen for output when I open the file to print because the sharpening needs to be applied for the specific paper and printer.
In the coming days, I am going to share how to sharpen images with different software and techniques. If there is any software you use and you want to know how best to sharpen your images with it, leave me a message in the comment box below. If you want to get updates of when I post, click the follow link below.
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