Editing Photos in GIMP: Using Unsharp Mask
Unsharp mask is a powerful but unpopular tool.
Sometimes photos need to be sharpened, it doesn't matter why, whether it is because of the sea mist that plagues anyone that lives by the coast or the pollution that haunts anyone that lives in the city, or simply because you just want to make your photo look a little bit sharper. Once upon a time, we would simply have had to write off a bad photo and move on, but now we can easily remedy a little bit of blur or a lack of crispness.
Unsharp Mask Can Improve A Picture
No matter what software you use (I use GIMP) the unsharp mask result will be the same, the process might be different, but what you will be left with afterwards will be the same, and that is a clear, sharp looking photograph. That is, if you have used it properly. It's a tool that is described by both Photoshop and GIMP as one of the most powerful ways to sharpen an image and reduce blur, but according to both companies, most of their users tend to shy away from it.
It seems really complicated, and it's a trial and error situation, but once you have got the hang of it and mastered the method and figured out the best settings to get the results you want then you will wonder how you ever edited your pictures without it.
One thing that I did for a while was just use the unsharp mask on it's own, straight onto the picture. It was looking sharper but I seemed to be losing a lot of color. So after some research I found a better way to do it by reading a very helpful GIMP tutorial. The tutorial explained that I had to decompose the color in order to stop the color from being lost. Being a beginner at the time, I found it really confusing and thought I would never get the hang of it, but decomposing the color and then composing it again (NOT recomposing, that is totally different) is really simple.
Step 1. Open whatever picture you want to sharpen, go to colors > components > decompose, where it says color model, choose HAS from the drop down menu, click the "decompose to layers" box and then click OK.
Step 2. Another picture will appear and it should look like the picture below. You will work on the decomposed picture. Go to Filter > enhance > unsharp mask, you can adjust your settings, but for this, I have used the default settings.
Step 3. You won't notice much difference until you go to colors > components > compose and once again choose HSV for the color model and click Ok.
The color will be restored to your picture and the unsharp mask will have been applied. It sounds more complicated than it actually is and once you have done it once you will find it really easy to do. This method prevents color distortion and improves the overall look of the picture.
When it comes to sharpening, the key is to make it look just that, sharper. Too much sharpening looks really weird and unnatural, and sometimes you have to admit that no matter how much you try to sharpen it, you can't completely rescue a photo. Sometimes the blur is just too much and sadly you have to write that one off to experience (it happens a lot where I love because of the sea mist!)
Sharpening a picture in post production is no substitute for getting it right "in camera" so always try to get as clear a shot as you can possibly manage. The less you have to clean up in editing, the better and more natural your pictures will look.