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- Understanding grayscale values and channels
- Evaluating and correcting images with histograms
- Saving to different file formats
- Managing color
- Cleaning the scanner and images
- Reproducing versus assigning colors
- Recognizing contone versus dot pattern images
- Understanding bit depth
- Scanning logos and line art
- Scanning transparent film, positive or negative
- Capturing high dynamic range (HDR) scans
Skill Level Intermediate
Earlier in this course, we discussed how important it is to calibrate, and color manage your scanner, why? So that we can get the grayscale values right. If we get the grayscale values right, our continuous tone images and our color images are going to be correct, and we'll be passing on to the rest of our workflow a tonally correct and color correct file. In this movie and the following movie, I am going to show you first how to calibrate your scanner using a ten step target and then we're going to follow that up and create a color profile for a scanner based upon an IT8 Target.
The first step here is going to be to calibrate our scanner and to do that, we're going to use this 10 step target that I have actually created and developed for use in digital photography and in desktop scanning. Each of these swatches, these 10 swatches here have a grayscale value assigned to them. An RGB value, 242 for the first one, 219 for the second one, 196, 173, 150, 128 for the midtone, 105, 82, 59, and 36 and the way this works is we scan this target, we do a preview of the scan and then we're going to measure the grayscale values that the scanner actually sees, and then we're going to compare those values with what are on this target, and if there's a difference, then we're going to apply a correction curve to our scanner so that when it looks at this target, it's going to see the grayscale values properly, and if it sees these grayscale values properly, then it's going to see the proper tonal values in our images properly, and then our grayscale and our color, contone images are going to be properly captured.
So let's dive right in, let's go on over to our scanner, here's our target that we pre-scanned and I will go ahead and pre-scan it again, so we go through the whole process. In this case, we're going to do a neutralization, which is the more complicated of the two calibration procedures. We can just do a grayscale calibration, which just involves getting one grayscale value correct for each of these swatches or we can do a color calibration. To do that, we'll choose a 48 to 24 bit Scan Mode, which means we're going to be capturing three 8-bit grayscale channels and we want to make sure that each of those grayscale channels has the proper tonal values on it.
So our goal here is to make sure that each of these swatches is captured accurately. To do this, we're going to use the expert function that's built into SilverFast and I know this is pretty intimidating, but when we step our way through it, I think you'll see how it works. What this allows us to do is adjust the scanner in these various tonal ranges and this is 255, this is pure white, and this is at 13%, and 25% and 50%, and all the way down to 0. What we're going to do is we're going to create color sampler points on a couple of key ones.
We'll put one at 242 which is the highlight, we'll put one at 173, one at the midtone at 128, and down here in the three-quarter tone at 82, and then we're going to measure what the scanner is actually seeing, compare that again to these values, and then come back and correct them with these input fields here. Okay. If you're not quite sure what's going on yet, hang in there and I think as we go, it will become clear. So the first thing we're going to do is we're going to create four color sampler points. We could do it for all 10, but I think if we just get four, we'll have a pretty good curve.
and we'll have a really good idea of what's going on in the scanner. Let's start with this highlight point here. It's supposed to be 242, 242, 242, and when we click on there, and we measure this, notice it's 248, 247, 246. Not bad, pretty neutral actually, and remember, this is not just a calibration like for grayscale. It's a neutralization, which means we're doing calibration on three channels, and when it looks at this grayscale target in RGB mode, all these values should be equal for each swatch.
This one is pretty darn close, isn't it? It's within 2, which is less than 1 % difference on a scale of 0 to 255. The 173 target, the number two, 174, 176, 171, pretty close, a little high on these two, just a tad low on that one. The 128 color sampler point, boom! The red is right on the money, the green, 130, blue is 125, these are slightly low, and then this value right here, 82, the green is right on and the red and the blue are a little bit low.
By the way, we should use this on a scanner that's fully warmed up for half-an-hour. So I will do a couple of scans and make sure that the temperature is up to snuff and it's the operating temperature for the scanner, because the response of the scanner will definitely change with temperature. And if you recall earlier in some of the movies I've talked about how important it is to work in a constant temperature environment and not have huge temperature swings. Well, this is the reason why, because we're going to calibrate and color manage at a specific temperature. How do we then neutralize the scanner that is calibrated on all three channels? Well, SilverFast provides this Expert- Dialog box here, which allows us to come in here and input RGB values at specific places along the tonal range.
Well, we're going to start up here by the highlight to at 242, and notice, we could come in here at 224, we're about halfway between the 255 and the 224. So since we're pretty close to the highlight, I am gong to come in here and I am going to start putting in some numbers that I think are going to be pretty close. And what I want you to do, while I do this is, watch these numbers here as I put in some numbers up here. I am going to go 246, because notice that these values are a little bit high, so I am going to lower these values here from 255 down, so we can lower these values there.
Let's try some values here, try 246, 246, and 249, and then, let's see what happens to our values over here. And see by lowering these values, now we're measuring these pretty close to 242, aren't we? We could Shift+Tab come back and notice that, that one is just a little bit too low, so we could put this one to 247, let's say, just to raise that a little bit, and honestly, one point of difference one way or another is not going to make a whole hill of beans. But we'll be pretty accurate here.
So now we've got the Highlight neutralized. Now, we're going to go down to the 173, and let's choose the area here that is closest, 192 is the closest. So let's try some values here, and we're pretty close on a couple of these, aren't we? We're right at 174, so we're going to keep that one to 190, let's put this one at 191, 190, and 193 and then just see what happens to our values here. We're supposed to be right at 173, which is perfect, we've got the red just right, green is up just by 1 at 174, and the blue is down just by 1 at 172.
So we're within 1, and honestly, we could just leave it there if you want to. If you're really anal, you can come in here and you can go up one value here and go down one value there, all depends on how anal you want to be. So we get it just right on the money at 173. Then let's go to the midtone and see how we're doing. Notice that as we correct the highlight and our quarter-tone, the midtone is already going through some adjustments here. We're pretty good. In fact we're right on the money on the red, so we don't need to address that one at all. The green is just a little bit high, so let's drop that one down to 126. Boom! Right at 128, and this one is just a little bit low, the 128.
So let's put that one at 130 and see what happens. 128, let's go up to 131, there we go! Now all of them are at 128. One more, the three-quarter tone, see this is at 82, so we're going to want to go to this one right here, which is the closest, which is 64. These are a little bit low, aren't they? The green is pretty darn close. in fact, this is right on the money. So let's go with 69 on this one and see what happens. Ooh Sweet! Good guess, we went right up to 82, and let's tab forward to the blue, and let's go ahead and put 69 on that one and see what happens.
Didn't quite make it, so let's go up to 71, right on the money. You can see slight changes in the curve that we have here. So we're making minor adjustments to how the scanner sees these values, and now we're just going to click OK to save these values. We've now calibrated our scanner on all three channels, which means neutralization, so that we know we have proper tonal variation from highlight to shadow, and we made minor adjustments in each of these swatches. 1, 2, 3, 4, true enough, we could do it on each and every one of these swatches and you'd get a little bit more accurate, but honestly, just doing these four points makes a huge difference in terms of the accuracy of the scanner.
As we move forward now, we're going to take this calibrated neutralized scanner and move to the next step, which is creating a color profile with a color IT8 target. So I am going to click OK to apply that. We've now neutralized the scanner for RGB, so that the RGB values. that are the tonal values in all three channels are now going to be accurate across the entire tonal range of this image.