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Photoshop CS3 Sharpening Images

Using Convolution Kernels for more accuracy


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Photoshop CS3 Sharpening Images

with Deke McClelland

Video: Using Convolution Kernels for more accuracy

Once again for those you who are fans of sharpening theory, I've got another theory exercise here for you. I was telling you at the end of the previous exercise how the More Accurate checkbox is based on the notion of a Convolution Kernel. A Convolution Kernel allows you to compare neighboring pixels to each other and exaggerate their differences or downplay their differences as well if you want it to. It's a primitive sharpening effect. It does a great job of bringing out noise inside of a digital photograph, which is one of the reasons you don't really want to work this way, but it also does a great job of sharpening the minutia in the image, which is what the More Accurate checkbox does.
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  1. 50m 30s
    1. Why every image needs sharpening
      2m 38s
    2. Understanding the effects of sharpening
      5m 26s
    3. Understanding the mechanics of sharpening
      4m 19s
    4. Understanding sharpening and gradual transitions
      3m 21s
    5. Understanding sharpening and noise reduction
      4m 0s
    6. Understanding amount and radius
      7m 50s
    7. Measuring your screen resolution
      6m 19s
    8. Using reliable zoom ratios
      5m 30s
    9. Calculating the actual print size
      4m 54s
    10. Gauging the ideal sharpening settings
      6m 13s
  2. 59m 31s
    1. Everyone knows you sharpen last (and everyone is wrong)
      1m 8s
    2. Understanding the conventional sharpening workflow
      5m 4s
    3. Flattening and saving to TIFF
      6m 39s
    4. Downsampling (and why you shouldn't upsample)
      6m 8s
    5. Understanding last-step sharpening
      6m 44s
    6. Recognizing problems with the conventional workflow
      9m 38s
    7. Erasing sharpening with the history brush
      4m 30s
    8. Using alternative sharpening workflows
      2m 37s
    9. Sharpening a scanned photograph shot on film
      2m 45s
    10. Sharpening a digital photograph
      3m 6s
    11. Sharpening specific details
      3m 43s
    12. Finding broad workflow conclusions
      2m 49s
    13. Learning that technique trumps timing
      4m 40s
  3. 1h 27m
    1. Comparing and contrasting neighboring pixels
      1m 6s
    2. Using the Gaussian Blur filter
      4m 25s
    3. Using Gaussian luminance distribution
      4m 47s
    4. Using the Unsharp Mask filter
      4m 54s
    5. Understanding the history of Unsharp Mask
      3m 51s
    6. Building your own USM with Gaussian Blur
      7m 35s
    7. Using the Smart Sharpen filter
      7m 35s
    8. Compensating for camera shake
      8m 50s
    9. Building your own Smart Sharpen with Lens Blur
      6m 59s
    10. Using directional sharpening with Emboss
      9m 13s
    11. Using Smart Sharpen extras
      8m 56s
    12. Using Convolution Kernels for more accuracy
      7m 8s
    13. Using the High Pass filter
      7m 32s
    14. Using Luminance Sharpening
      5m 5s
  4. 2h 14m
    1. Smoothing filters, smart objects, and masks
      1m 25s
    2. Using the Median filter and Dust and Scratches
      7m 7s
    3. Using Smart Blur and Surface Blur
      6m 12s
    4. Using the Despeckle filter
      8m 17s
    5. Softening flesh tones selectively
      10m 15s
    6. Using the Reduce Noise filter
      7m 27s
    7. Combining smoothing and sharpening
      8m 24s
    8. Making an image into a smart object
      9m 24s
    9. Applying editable smart filters
      6m 8s
    10. Combining two smart filters
      8m 5s
    11. Assigning a filter mask
      5m 59s
    12. Nesting one smart object inside another
      10m 32s
    13. Employing a static High Pass layer
      8m 59s
    14. Matching static pixel-level edits
      4m 37s
    15. Avoiding clipping with luminance blending
      9m 7s
    16. Sharpening and smoothing
      6m 36s
    17. Making an edge mask
      8m 14s
    18. Making a non-edge mask
      7m 17s
  5. 1h 33m
    1. Sharpening with Adobe Camera Raw
      1m 29s
    2. Introducing Camera Raw (4.1 or later)
      8m 13s
    3. Understanding why to sharpen for source
      5m 14s
    4. Using Camera Raw’s sharpening control
      5m 52s
    5. Previewing limitations and tricks
      6m 45s
    6. Why downsampling doesn’t work
      3m 12s
    7. Reducing chromatic aberration
      7m 30s
    8. Using the Defringe option
      3m 32s
    9. Understanding high frequency, low radius
      5m 21s
    10. Raising the Detail value
      3m 6s
    11. Using on-the-fly edge masking
      5m 41s
    12. Sharpening a low-frequency portrait
      6m 36s
    13. Eliminating color noise
      4m 47s
    14. Reducing luminance noise
      4m 42s
    15. Correcting “false sharpening”
      7m 15s
    16. Reducing shadow noise
      5m 22s
    17. Approximating ACR sharpening in Photoshop
      8m 35s
  6. 59m 8s
    1. Gauging and exploiting luminance frequency
      1m 27s
    2. Using low-frequency source sharpening
      5m 53s
    3. Using High Pass for portraits
      4m 19s
    4. Actioning a low-frequency edge mask
      7m 42s
    5. Modifying the source sharpening
      5m 21s
    6. Using high-frequency source sharpening
      5m 26s
    7. Using Smart Sharpen for cityscapes
      3m 2s
    8. Actioning a high-frequency edge mask
      5m 4s
    9. Downplaying color artifacts and clipping
      4m 4s
    10. Sharpening a medium-frequency image
      5m 24s
    11. Sharpening a layered composition
      7m 16s
    12. Sharpening for multiple frequencies
      4m 10s
  7. 1h 8m
    1. Who needs dull when you have sharp?
      56s
    2. Focusing in on a person’s eyes
      4m 22s
    3. Blurring the area outside the eyes
      4m 22s
    4. Sharpening eyes and other details
      5m 38s
    5. Darkening the lashes and eyebrows
      7m 13s
    6. Sharpening dark-haired people
      5m 2s
    7. Edge mask and emphasize
      3m 39s
    8. Nesting a Smart Sharpen effect
      4m 48s
    9. Density mask sharpening
      5m 35s
    10. Adding depth of field
      4m 39s
    11. Sharpening a background
      4m 23s
    12. Masking background from foreground
      8m 51s
    13. Eliminating halos around a person
      5m 38s
    14. Deepening and warming a background
      3m 28s
  8. 1h 18m
    1. Reverting back to convention
      1m 37s
    2. Understanding the use-neutral composition
      4m 15s
    3. Restoring much-needed antialiasing
      4m 2s
    4. Reducing noise in a high-frequency image
      7m 24s
    5. Making a third-level smart object
      3m 55s
    6. Preparing an image for print
      5m 18s
    7. Using ideal settings for commercial reproduction
      5m 37s
    8. Calculating very large-format settings
      5m 11s
    9. Using ideal settings for inkjet output
      4m 26s
    10. Sharpening for commercial reproduction
      5m 45s
    11. Sharpening for inkjet output
      4m 58s
    12. Revealing high-frequency multipass sharpening
      5m 21s
    13. Using Gaussian Blur to sharpen hair
      5m 41s
    14. Flatten, Save As, Resample, and Sharpen
      5m 9s
    15. Revealing low-frequency multipass sharpening
      3m 30s
    16. Sharpening an image for web or screen
      6m 22s
  9. 1m 50s
    1. Goodbye
      1m 50s

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Photoshop CS3 Sharpening Images
10h 33m Intermediate Feb 15, 2008

Viewers: in countries Watching now:

Real focus happens inside the camera's lens element. The sharpening features in Photoshop CS3 exaggerate the contrast along edges in a photograph to transform a well-focused image into an outstanding image. In Photoshop CS3 Sharpening Images, Deke McClelland teaches a host of sharpening and noise reduction techniques, including using filters such as Unsharp Mask, Smart Sharpen, High Pass, and Reduce Noise. The training teaches the essentials of sharpening, including what it does, why it's important, and how the filters function. Plus, the training covers Deke's recommended best practices, including the four distinct varieties of sharpening, which can be used independently or in combination with each other. Photoshop CS3 Sharpening Images is about how to transform images from looking good to looking their absolute best. Exercise files accompany the course.

Topics include:
  • Understanding the effects of sharpening
  • In-depth examinations of Unsharp Mask, Smart Sharpen, Emboss, and High Pass
  • Smoothing an image with the Surface Blur, Despeckle, and Reduce Noise features
  • Working with smart objects and smart filters
  • Creating edge masks and non-edge masks
  • Sharpening for digital-image capture using Camera Raw
  • Gauging and exploiting luminance frequency
  • Exploring creative applications of sharpening
  • Sharpening a multilayer composition
  • Sharpening eyes, hair, and out-of-focus backgrounds
  • Reducing noise in a high-frequency image
  • Determining ideal settings for commercial and inkjet output
  • Sharpening very large-format images
  • Sharpening an image for the web or screen output
Subjects:
Photography Sharpening
Software:
Photoshop
Author:
Deke McClelland

Using Convolution Kernels for more accuracy

Once again for those you who are fans of sharpening theory, I've got another theory exercise here for you. I was telling you at the end of the previous exercise how the More Accurate checkbox is based on the notion of a Convolution Kernel. A Convolution Kernel allows you to compare neighboring pixels to each other and exaggerate their differences or downplay their differences as well if you want it to. It's a primitive sharpening effect. It does a great job of bringing out noise inside of a digital photograph, which is one of the reasons you don't really want to work this way, but it also does a great job of sharpening the minutia in the image, which is what the More Accurate checkbox does.

So I am to going to show you a Convolution Kernel. I am not suggesting this is the way you work once again, just a little bit of theory I am going to show you a Convolution Kernel and then we'll see how it compares to the better More Accurate checkbox. I am working inside the test shapes.PSD image which is found inside, once again, inside the 03 sharpen filters folder. I am going to go up to the Filter menu and I am going to choose Other and I am going to choose this guy right here, Custom. The Custom filter allows you to multiply the luminance levels of pixels inside of an image and then add them together or subtract them from each other. Do all this wacky stuff.

Here's the idea. It's little hard to understand if you've never seen it before' which 99% of Photoshop users havent. Basically whats going on is, remember I was telling you that all of the sharpening filters inside of Photoshop and Gaussian Blur, the Blur filters as well and the Averaging filters, are actually scrubbing through the image. So you imagine all these little scrubbing bubbles going through the image and at any nanosecond of time you are evaluating a single pixel inside the image and trying to decide how to change that pixel or at least that's what Photoshop is doing, its making a decision based on the luminance level of that pixel and the luminance level of the neighboring pixels on a channel-by-channel basis incidentally.

So whats going on inside of this 5x5 grid is were seeing a grid of 25 pixels. So 5 pixels wide 5 pixels tall, right there in the center that's that one pixel that's being evaluated at any given nanosecond in time, and right now according to the default settings we are seeing, multiply the luminance level of that one pixel by 5 and then look at the pixel directly above it and multiply it times -1, so subtract its luminance level and take the guy directly to the right and subtract him and take the guy below and subtract him and take the guy immediately to the left and subtract him.

So if you do the math here, which is pretty simple: 5-1-1-1-1, that's 5 minus 4, so that's 1. So in other words we are attempting to maintain a consistent level of brightness inside of the image. If I were to raise this value to six, so the math is of, its now 6-1-1-1-1, so 6 minus 4, it gives you 2. We're essentially doubling the brightness of the image. If I were to take this value down to 4, so that the sum is now 0 instead of 1, we are darkening the image.

Don't worry about Scale and Offset. This is just going to multiply the overall effect and this one is going to add or subtract luminance levels, you typically don't want to work with them, you want to leave them alone. Actually you probably want to give this filter the path in general, but you can't, there are things you can do with it, you can create these really cool like sort of Color Emboss effects if you want to and you can do some blurring and you can enter all kinds of values inside of these various option boxes and play it to your hearts content. All you want to make sure, those of you who are comfortable with arithmetic, you just want to make sure that all your numbers whether positI've or negatI've they all add up to one.

So the end result is one, so I could enter 9 here for example and then a -1 here and a -1 here and a -1 here and a -1 here and now we have eight -1s, so we have 9 minus 8 and that's going to give us 1. Once again, so we are maintaining a consistent level of brightness. Now when you have a positive value in the middle and negative value surrounding it, you get a sharpening effect and so the default value, I'll go ahead and press the Alt key or Option key in order to change the Cancel button to Reset and I'll click on it and that will give us the original values which are 5 surrounded by -1 that gives you the most basic sharpening effect that you can apply essentially inside of this dialog box, so this is the lowest level sharpening and you can see how Photoshop is going in there on a really granular basis.

This is before and this is after, and applying the sharpening on a pixel-by-pixel level essentially. So theres no such thing as radius or halos or any of that stuff, you don't have that kind of control. You are just exaggerating pixel differences. So I'll go ahead and click OK so that we have that saved up and I'll go ahead and zoom-in, and when I say, "Its saved up, its stored now inside the History palette, so we can come back to it. Then I am going to go to the File menu and I am going to choose the Revert command so I am bringing back the original version of the image inside History so we can work with a flat file which is important just because for demonstration proposes I am using a flat file.

Later we'll be using layers which is a better way to work. So having reverted the image, now I am going to go up to the Filter menu, I am going to choose Sharpen and then I am going to choose Smart Sharpen. The idea is, we're going to compare the effect of the More Accurate checkbox, and this time I am going to change the Amount value something like 200%. I think it would work better for us. Lets take this Radius value down to 2 pixels, we've got Lens Blur, now lets turn on More Accurate and you'll see the difference, you might be able to see it there, lets go ahead and zoom-in a little bit so that you can see it little more closely.

So this is what this image looks like without More Accurate, this is what it looks like with More Accurate. So it's bringing out even more information inside the texture detail. So it's over-highlighting essentially the texture and it's not doing much to the big details at all. So its highlighting that high-frequency information and ignoring the low-frequency information that's already been treated by the other values here and as a result we are making this sort of textury effect look almost leathery inside of this particular image.

So I would say with this image More Accurate could be a good thing if you decide to go there out, because this isn't a portrait shot, it's a high frequency shot, so that's a good thing. Whenever you want to exaggerate the high-frequency details, that's when you turn on More Accurate. And well see more examples of this when we take a look at sharpening details in a later Chapter, but for now there it is, I am going to click OK and just so that we can compare the two effects I am going to move this guy over a little bit, bring up the History palette and this is what the Custom Convolution Kernel looks like and this is what the Smart Sharpen effect looks like.

So if you were to compare them very closely you would see that the Custom effect is very detailed, but its also very choppy, we have some razor like lines going on and we have some jagged transitions as well, whereas Smart Sharpen is a little more rounded, its a little more defused and its ultI'mately a better effect, but again, More Accurate hails from days of Convolution Kernels because it gives us that control over sharpening the high-frequency details inside of the image.

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