In the MagicTune utility you face with several monitor settings, without real explanation. This page tries to explain what do the settings do in the case of Samsung 970P (as far as I could find it out). It's mostly for those who take an interest in technical things, but I hope it also helps to find the optimal settings for you.
Attention: What I write on this page is based on what my eyes see, not on any technical documentation.
MagicTune does the same thing like if you press the adjustment buttons on a monitor (just 970P doesn't have any buttons physically). That is, it adjusts the monitor itself (by communicating with it through the video cable using DCI protocol), and not what the video card sends to the monitor. This is an important difference. This is why setting things with MagicTune is not always the same as setting them with the control panel of your video card (like with Catalist Conrol Center). Setting brightness/contrast and like with your video card usually should be avoided, as the monitor is in better position to addjust these things.
As you should know, in the computer world colors are from red, green and blue components (RGB), often referred as the 3 primarily colors. For each pixel, the brightness of the 3 primarily colors are handled separately in the video card, as an integer number in the 0-255 range, which gives 256 possible shades (brightness levels, that is), where 0 means total darkness and 255 means the brightest possible shade. (For internal calculations video card may use much finer shade steps, but it's irrelevant now.) So each pixel is represented as 3 numbers, like a possible dark orange color is [255, 127, 0] (that is, red is on its maximum brightness, green is near on half brightness, and blue is turned off). Due to the rules of color mixing, for grays these tree numbers are the same. For example [127, 127, 127] is a middle gray, [64, 64, 64] is a dark gray, [255, 255, 255] is white, and [0, 0, 0] is black. For practical reasons I will mosly only deal with grays on this page, and I will refer to a gray color as only one value, like by 64 I mean [64, 64, 64].
How do monitors relate to the color model of the video cards? They use the RGB idea too, but as analog devices, they were not interested in the number of shades (256 per primarly color), until now. TFT monitors are more digital in nature than the good old CRT-s, and (in 2006) are rather limited when it comes to the number of possible shades (brightness levels) of the primarily colors. Like, as far as I can tell, 970P can only display 64 brightness levels per primarily color, but it uses a trick called dithering to seemingly achieve 253 (0-252) possible brightness shades per primarily color. And if you think a bit about it, even if it could be able to display 256 levels (like a real 8 bit TFT can), it's still not enough because you are allowed to set brightness, contrast and gamma, which introduces much more possible shades. Note that this has nothing to do with the video card; it's how TFT panels work, doesn't mater where they get the signal from (like from your VHS player's composite video output, which doesn't even use RGB).
So, we have an image inside the computer that uses 256 shades (0-255) per primarily color. This image data is sent to the TFT through the DVI cable. Then the monitor has to apply its brighness and contrast and whatever settings on this received data. Then it has to convert the result to 253 shades in the case of 6 bit monitors. Looking at this whole process as a black box, what's happening is that you map integer numbers in the range of 0-255 to integer numbers in the 0-253 range. This of course can't be done without loss, no mater what monitor settings you chose.
Note: To play with brightness/contrast/gamma settings, get a good gray gradient image, like this.
I assume you set brightness to 50, gamma setting to 0, turn the color temperature setting off, and also you didn't run calibration yet (or did but then have disabled it), otherwise the numbers written here later doesn't exactly stand. Then, if the contrast is 50, the mapping of the video card's color to the colors of the TFT (see in the previous section) is like this:
As you can see, just as technically interesting fact, you get an ideal gradient here in the sense that the brightness steps are totally uniform (however because of the dithering trick you will still see some strange textures cluttering it). Except that the last 3 gray shades are lost, since they are all white. This means that very bright objects on white background (like a watermark) will be hard to see or even totally invisible.
(Note for DTP/photographer and other technically involved people: The vertical axis of the diagrams corresponds to the luminance, but it uses a non-linear scale, so that with the "native gamma" of the TFT it looks like a straight line.)
Decrease the contrast bellow 50:
Now you don't lose the bright grays, but you have a lot of repeated colors, since the steepness of the line is bellow 45° and we have less than 256 shades on the TFT. This causes visible breaks in the uniformity of gradients, because some neighbor colors will look exactly the same. But since you will hardly watch gradients in practice, don't worry about this too much; it's more important that you find the image pleasant for your eyes, or that you don't lose those bright grays. The higher the contrast is, the least color repeats you have, if we don't count those light grays that stuck into white. I have found that contrast 48 is the highest value where no bright gray becomes to totally white (assuming gamma is 0, etc).
If you increase the contrast over 50:
As you can see, you will lose more and more light grays. Also, you will have uniformity breaks in the gradients, as the brightness sometimes jumps 2 instead of 1. (But again, uniformity breaks are not a big problem in practice, and anyway most probably you can't avoid them, since they are present with almost all settings.)
So, contrast sets the steepness of brightness mapping line (the red line of the above figures). But, as you can see, the left end (0) of the line is always remains at 0. Thus, whenever you increase the contrast, you also increase the overall brightness of the image. But what does the brightness setting do then? Guess what, it does exactly the same as the contrast setting, as far as you don't go above 50 with it! The steepness of the line is specified by the contrast and the brightness together. Like, if you set the contrast to 0 and brightness to 50, that's exactly the same as if you set the contrast to 50 and the brightness to 3 (why not 0, I don't know; there is a little asymmetry). It's that redundant... As far as you don't exceed 50 for the brightness, it really doesn't mater if you set the brightness or the contrast; they are the same (ignoring the minor asymmetry, like 3 instead of 0 above). However, to achieve a very flat line (very low contrast), you will need to decrease both settings, so they have enough "flattening power" together.
Over 50, brightness sets the strength of the back-lighting, and doesn't effect the steepness of the brightness mapping line anymore than if it's at 50. This way it increases the brightness without causing any additional unwanted artifacts (like color repeats, jumps or light gray loses; it's because the staggered nature of TFT monitors is caused by the "glass + LC + source drivers" part, which is independent of the back-lighting). (I have found that this 50 value is fix, whatever gamma or color temperature setting I use.) The back-lighting is basically just a lamp that uniformly lit the whole panel (i.e. it can't be controlled per pixel), so it increases the brightness of all colors, even of black. So you will have less and less deep black as you increase the brighness over 50. But don't worry, due to the laws of physics and the nature of human eye, the lighter a color is, the more its apparent lightness will increase with the back-lighting strength, so this negative effect is not significant with this model (but can be significant with others).
Note that as the brightness mapping line (the red line on the figures above) approaches it's maximum on the "displayed level" scale, the white and the light grays will be a bit yellow. (Setting a cooler color temperature can't eliminate this.) This phenomenon was present on all TFT monitors I have seen so far. If the line is flatter, this phenomenon will be reduced, however of course then you lose from the number of possible shades.
To sum it up, the monitor can do these two things in connection with the brightness and contrast settings:
Change the strength of the back-lighting (which is uniform for the whole display). This is set by the brightness when it's over 50.
Change the steepness of the line that maps the brightness values of input to the actually displayed brightness values. It's set by the brightness and the contrast together, however, brightness over 50 is the same like brightness 50 regarding the steepness.
Thus, for the best results, a simple recipe is to keep the contrast at 50, and only use the brightness slide. If brightness 0 doesn't give you dark picture enough, start to decrease the contrast.
The gamma setting specifies if how much concave/convex the brightness mapping line is. Here it is in pictures, using the same system as with the contrast/brightness settings:
(Note: If you are looking for the definition of gamma as in gamma correction, you are at the wrong place. This is the gamma setting of the 970P, which is related, but not the same. Especially the diagrams above use different axes than the ones in technical literature.)
With higher gamma setting you will lose details in darker colors, but will see more details in lighter colors. With lower gamma setting you will see more details in darker colors (can be useful in dark movies and, I assume, in dark games), on the expense of losing details in the lighter region. Of course, at the points where the line is not 45°, you will have repeated color or color jump artifacts, exactly like as it was shown for the contrast setting. But those artifacts are not a big problem as far as you don't watch gradients.
Note that although with a certain gamma setting you see more from the dark or light areas of images, the image may doesn't look as its author (who has used a monitor with a more standard gamma) has intended, and/or the image (like photos) doesn't look natural.
This will find with your help the monitor setting modifications needed to compensate the factory variance and the possible wear-out of the display, so you achieve a natural lookig image. Give it a try. (Unfotunatelly the monitor is not here anymore, so I can't test this, so I can't tell much detals... sorry.) After calibration the corrections will be always applied, on top of the settings that you chose in MagicTune. That is, setting the brightness, gamma and whatever slides to the same position (to the same numerical value) will not result in the same image as earlier.
Out of the box the monitor simply doesn't not apply any corrections (so this is the state where you can achieve the perfectly 45° brightness mapping line with the earlier said settings; but that's not a goal anyway, just good to know for your experiments). To reset the monitor to this uncalibrated state, I have run the calibration again, and simply saying for everything that it's good now without changing the initial position of the calibration slides.
This changes the color of the image towards blue in the case of "cool" settings, and towards orange in the case of "warm" settings, as you can see. This is of course done by recalculating the R, G and B values for each pixel before they are displayed (not by changing the color of the back-lighting or something like that). So there is an artifact regarding this again. Since the monitor can display only a low number of possible shades per primarily color (253 in this case), the proportion of them can't be kept precisely on the desired value. Thus, if this setting is not "off", some gray shades will be more blue or yellow/orange than the others. This is well visible on a gray gradient, but again, I don't think that's important in everyday usage.
Also note that if color correction is not "off" (or at least if it's "cool 1"), then you considerably reduce the brightness of the display (which is not a problem; this monitor can be way too bright). This also means that numerically higher contrast/brightness can be set without losing some of the brightest grays (they used to become white as I have explained earlier).
Personally, I have found that the "cool 1" setting gives the most realistic colors in general. In the "off" setting the image is too yellow/orange for me. However, I have also found that "cool 1" is more tiring for my eyes than "off". But that's maybe just me... it seems that blue light hurts my eyes.
Sorry, but it depends on your eyes, and the lighting of your environment. And, most importantly, on what you are doing. For example, I use these:
I have to admit that I have left the gamma on 0, and haven't played much with it... and the monitor is not here anymore, so I can't say anything about that.
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