Adobe Photoshop Image Restoration Tutorials
Basics / Increasing the Sharpness/Detail of the Image
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Subtitles of the Movie (Adobe Photoshop Image Restoration / Basics / Increasing the Sharpness/Detail of the Image)
Let us turn our attention just a little bit to another process to improve the appearance of your image and that will be sharpening. Really sharpening is just another way of describing the increase in focus on an image. If you do it right, it can really improve the appearance of your image. If you do it wrong, it will degrade your image considerably and I have seen images that were over-sharpened and then it really looks horrible. So let us look at how to do it right and first thing you have to understand in order to be able to achieve the correct sharpening level is to understand how it works. So let us take a look at two photographs. I love to listen to people talk about the sharpening that they do and they always say well, we sharpened it with x number of settings without any discussion whatsoever about what the original resolution of the shot was, because that is an integral part of the sharpening process is to know what your original resolution is so that you can choose the right settings to get the desired result. I am going to explain to you how this process works. Now we have two photographs here; one is a JPEG, it is low-res, only 72 dpi. This is a 300 dpi TIFF image, and obviously it is larger, this is a seven meg file, this is a three hundred and seventy-one KB file and so there is a whole lot more color information here than there is there. Now these are the same size as far as the dimensions on the screen are concerned, and they do different things when you apply the sharpening process to them. But for the purposes of demonstration, let us look at the high-res image, and we are going to increase the magnification on this image considerably, we are going to look at this area of Cynthia's hair, and since it has got quite a bit of detailed contrast, let us go and take this up to the pixel level so that I can demonstrate to you what happens in the sharpening process. Now by definition, sharpening is really nothing more than an increase in contrast between adjoining pixels. Now how does that differ from contrast and brightness adjustments in Photoshop in other applications? It differs because this sharpening process is occuring at the pixel level. The contrast adjustment on a photograph is occurring at the tonal adjustment, in other words over certain shades of color and not at the pixel level. Sharpening is a pixel level, very finite adjustment that does nothing more than increase your focus. So what do we use to sharpen? Well there are a couple of different ways to achieve sharpening, but the most popular is the unsharp mask. I will get into details about how to use the unsharp mask later but just so that I can explain to you the theory of sharpening, let us take a look at all of the different adjustments that can be done. Now this is an untreated photograph. Remember we have got strands of hair, with the light area, dark, lighter, dark and so on. So we have an adjustment here of a hundred percent, meaning we are going to double the contrast, we are going to double the intensity of the light images and we are going to double up the darker images. The radius of two pixels means that for every other pixel, we are going to make an adjustment. The threshold is three levels, doesn't really have a mathematical application, it is more of an abstract representation of where these top two adjustments are going to be affected. The greater the number, the less effect of sharpening you are going to get, the lower the number, the greater the sharpening effect you are going to get. That is basically all you really need to know, if we just used these settings on the high-resolution shots, here is what we get. Now I want to increase the amount of sharpening so that you can see this but when I click on that, can you see how the darker pixels are reduced in brightness and the lighter pixels are increased in brightness. This is not done on the tonal level now, keep in mind this is pixel-level adjustment. You see the increase in contrast there it is occurring on the pixel level. Do it again, that is before and after. Now let us increase the amount, let us take it up to five hundred pixels, just to show you what happens. That is a very pronounced amount of sharpening, too much, that would be too extreme for this image. Let us take it back to a hundred, and it barely moves, I doubt that you can even see it in this tutorial, but it barely moves. Now let us make another adjustment, let us take this down to say zero point eight, and I use that quite a bit for JPEG images, you cannot even see it. Let us take this back up to five hundred and you can barely see it. The radius is how far out, in other words, how far out from dark and how far out from bright are we going to affect these changes. So the greater number of pixels, see there, is the greater amount of contrast that you achieve on your result. Some of these concepts are a little bit abstract and you've got to get a feel for it, you've got to practice. You really have to practice with the unsharp mask to really master it, but I want you to see these as they are affected, and the best way to do it is just to do it and let you watch it and go from there. But it is a very, very useful tool, and if you do it right it is a wonderful thing, if you misuse it or you do not understand how it works then you are going to screw up your images even more than they were before you started messing with them. But that is the theory behind sharpening, now let us move on and see the various tools to achieve that result, and the first thing we will look at again is the unsharp mask, and what I am going to do is show you the difference between a low resolution image and a high resolution image.
Tutorial Information
| Course: | Adobe Photoshop Image Restoration |
| Author: | Phil Hawkins |
| SKU: | 33473 |
| ISBN: | 1932072705 |
| Release Date: | 2004-01-27 |
| Duration: | 4.5 hrs / 77 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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