Sharpening images can be a delicate balance between too much and too little.
This difference can ruin a great image especially when printed larger than the usual 6 x 4 print.
Many of today's modern digital cameras have the ability to sharpen images within the camera.
This is fine for the snapper who will only print their images in small format if at all.
The serious photographer will need more control of their work; so all image manipulations should be carried out of the camera.
To sharpen an image we are basically making the image to appear clearer and crisper. This is done by boosting the contrast between pixels. So lighter pixels will become lighter and the darker pixels will become darker.
Luckily we do not have to carry out this procedure ourselves, instead we can use the strangely named Unsharp Mask Filter in Photoshop. This filter seeks out the lighter and darker pixels in our images and applies our desired levels of sharpness to them for us.
Note - Sharpening cannot be used to make an out of focus or blurry image appear in focus or clearer.
There are three main controls in the Unsharp Mask Filter that control the level of sharpness added to the individual pixels of the image.
Amount - This adjusts the severity of the definition of the effect on each pixel. Usually a setting around 100 works well.
Radius - This decides how many pixels are affected around the edges of the sharpened pixels. To retain detail a setting of between 0.5 and 1 are best.
Threshold - this tell the software how different the pixels around the edge of the affected pixels have to be before they too will be affected by the filter effect. A setting of 0 will allow all pixels to be affected by the filter.
An overly sharpened image can look awful and knowing what to avoid will prevent you from getting some ugly results when you print your photos.
Halos - If the amount slider is pushed too high a dark or light glow can appear around the edges of your detail. This will give an unnatural appearance to your image
Noise - Noise or graininess can happen within the smooth areas of your images, such as skies, if you sharpen your images too much. Zoom in close when using the Unsharp Mask tool to check this is not happening.
TIP -When using the Unsharp mask always set the view image amount to 100% to see how the sliders are affecting the pixels in your image.