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Adobe Photoshop Image Restoration Tutorials
Basics / High Pass Filter
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Subtitles of the Movie (Adobe Photoshop Image Restoration / Basics / High Pass Filter)
Let us take a look at another method for achieving sharpening that works in some cases. You will be presented with situations that the high pass filter is really the better way to achieve a good sharpening result. You won't see this too often, but you will see it enough where you should be familiar with this process and the reason why we are not going to use the unsharp mask for this process is because, as we discussed when we were looking at the picture of Karen here, the background is a contiguous tonal range with very little variation, there is virtually no contrast in the background on this image, so it is very easy to adjust the threshold adjustment in the unsharp mask, to segregate the background from the foreground and achieve the desired result. In this particular image, however, we do have contrasting information in the background, although it is out of focus. We have very good depth of field in this photograph; there is still contrast in our tonal information here, and the unsharp mask is going to pick up on that and try to adjust this portion as it will this portion. That is what we do not want, we do not want to fight that battle. It is just a lot easier to do an end around and go with another process to achieve this sharpening result and leave this area here almost one hundred percent untouched, which is what we were looking for. This is a fifty-six mega-pixel image, very high resolution scan, and we do this for a reason, four thousand dpi is where I usually try to get all my scans done, so this may work a little bit slow but the way we begin this process with the high pass filter is we duplicate a layer and we call it a background copy and we change the opacity down to fifty percent. This is a very important part of this process and that is what it looks like. Then on the background layer we apply the high pass filter, now I have got it pegged up here because I was practicing with it before we actually began this particular lesson. But you will find high pass filter down under other, under the filter drop-down list, it is under other at the very bottom and high pass is you want to get. Now when you click on the high pass filter, you will see an adjustment that can be done on this filter, and it is important to adjust. You can do this visually, and it is important to adjust correctly on this thing. You want to focus out and see how we have just Sherry's image here, we do not have anything in the background showing right here. We can boost this, as we boost this, the background on the high pass filter starts to show through. What we want to do is adjust this down so that Sherry's outline is showing up here and we are not getting any background right here. It is kind of tricky, you've got to play with it; it's like anything else in Photoshop, there is no one way to do it. You suggest a way that you think it looks good but what you are trying to do is to reject this background information, and that right there looks like it is going to be about the best. You click OK and that is going to apply, then you come up here and you flatten your image, you merge your visible layers, then you go up to your image - adjustments - levels, and let us see what the automatic button is going to do. And that brings it right back to where it should be, or does it. I think it needs to be warmed up a little bit, let us do it manually just for giggles. Here is our histogram, very narrow histogram; this took a lot of mid-range in that image, that is just the result of the high pass filter and what it does. We bring these in, we increase our contrast and that looks better than the auto button, because I did not like that automatic color adjustment that they put on it. There you have it, that is how it is done. This is before and this is after. Notice we have done very little, maybe one percent adjustment on the sharpening on the background, which is what we wanted to achieve. We have got a real good result on the forefront image, before and after. Now keep your eye on the background, see if you see any difference. It changes very very little. Try this at home and I think you will be very pleased with the result. This will print very, very well. The other thing that is very good about the high pass filter in this situation, see the texture of the hat right up here, this is a mesh hat and on the unsharp filter you get a herringbone pattern; with a high pass filter you do not have any of that. The high pass filter works really well in certain particular situations. Practice with it.
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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