Improving Blurred Images

Sharpen tools usually have a "power" or "strength" setting (or "amount" in Picture Publisher). This controls the strength of the effect, obviously. Although you might be tempted to throw this setting up to maximum and go, this isn't always the best way, as it can lead to over sharpening. Unusually hard and bright edges are a sure sign you've gone too far. Take it a bit easy.

Let's see it in action then. As usual, the original is first, followed by the improved version. You should just be able to see on the thumbnail images that the second image is a bit sharper. Click the images, and have a look at the larger versions. The second one is noticeably sharper. Good. Mission accomplished.

Picture Publisher provides a few extra options, which might have helped. Note that "method" settings. By choosing "soft edges" as our method, only the side of the building (where the edges are indistinct) would have been affected. The hard edges where the building meets the sky, which we aren't interested in, wouldn't have been affected. This would have looked slightly better.

If the image had more colour variation, the "Lightness only" option would have helped preserve the colours' distinction, without blurring them at all (yes, the sharpen tool blurs the colour boundaries slightly). As this picture is mostly one colour, we don't really care.

For the power user who really needs more sharpening ability, the tool you need is the Unsharp Mask.

Yes, despite the deceptive name, the Unsharp Mask (or Unsharpen tool) increases the sharpness of an image in emmense amounts - far more than normal sharpen tools. At the same time, the effect is usually a bit smoother and more even, although you still have to watch those controls! Over adjustment is very easy. Incidentally, the Unsharp Mask was originally a photographic technique, but now we have our own computer equivalent. Let's take a look at it.

Again, the Unsharp Mask tool from Picture Publisher has a few options associated with it (as will most versions). The easy one is "strength" - the power of the effect, like in the sharpen tool. The threshold control basically sets the level of edge in the picture required before the unsharp mask takes effect. A high threshold means only well-defined edges will be sharpened any more.

The final control is the radius or area of the effect. Setting this higher produces much greater sharpening. Keep it low - it is easy to adjust this too high. If you want more sharpness than the default values allow, adjust the radius upwards, but decrease the strength (or possibly increase the threshold) to reduce the effect back to sensible levels. You will still get much more sharpening.

Let's see the effect then. Below, I have put side-by-side the original image, the image with the sharpen tool, and the original image with the unsharp mask applied. You should be able to see on the thumbnail images that the unsharp mask has produced a much sharper end result. Probably too sharp, in fact. As I say, you have to be careful with those controls. Click the images, and have a look at the larger versions.

Original Image	Image with Sharpen Tool	Image with Unsharp Mask