Choosing the best TV or projector we most often do not suspect that the main conclusion on the eve of purchase can be made if by some miracle we measure a few important parameters. One of them is the gamma curve, which will objectively show the color capabilities of your favorite model. Before we can clearly demonstrate how gamma affects the image on the projector or TV, it is necessary to go a little bit deeper into the theory. The root of the problem is that the human eye sees differently than the camera or any other device.
Consider a standard gradient running from black to white and containing 256 grayscale levels from 0% to 100%, that is from 0 to 255.
This strip shows how a digital camera sees the transition from the dark side to the light side – the transition is very smooth, linear. But the human eye sees the same strip very differently. Nature has arranged it so that we always “squint” in the dark side, and light colors – like evaporate, we almost do not perceive them.
The simplest example is to open any black and white photo: most of the tones gray levels on significant objects will be in the left half of the gradient, in the darker.
There is one more problem: linear coding cannot convey a sufficient number of gradation levels of dark tones. This means that with linear processing of the light flux gray tones and halftones will disappear: darkness for our eyes will come as abruptly as a southern night.
If we encode in 5 bits 32 levels of gradation , we will see the following “gradient.
As you can see, the gradient bar is “cut” much less frequently on the dark side than on the right edge. The lighter the picture, the more hues. But the point is that we almost never perceive the light part of the gradient, and that’s why most of the colors will just “dissolve” in our perception.
Conclusion: linear encoding of a signal distorts perception of an image by depriving it of natural colors.
That’s where the clever mathematicians came up with a way to trick your own vision – with a gamma curve. This stepped function improves the detail in the dark tones at the expense of its loss in the light tones, where all the same for us “all the cats are gray. And it does it very nicely – without increasing the amount of information being transmitted.
Thus, a lot of shades that were “blown out” and dropped out during linear coding of the signal are returned to the zone of visibility. The gamma curve shows how accurately the grayscale is reproduced in terms of lightness.
Most often a gamma curve with a factor of 2 is taken as a reference image for modern digital devices.2. The gradient in this case will look like this:
Notice how evenly spaced the gradient is and how many tones have appeared in the light area available to our vision? Thanks to gamma correction. The beautiful science is math!
To see with your own eyes what wonders gamma-correction can do, here are some color pictures with different gamma: 1.0 that is, without gamma, linearly coded , 1.8, 2.2 i 3.0.
A significant difference, isn’t it??
By the way, some of these frames may seem to be more contrasting than others, but that’s not so. The black and white dots in these images are identical, and so is the contrast. So the gamma value is much more important for the “contrast” of an image in the everyday sense of the word.
Can someone please explain how the gamma curve plays a role in selecting the right projector or TV? How does it enhance the viewing experience and improve color accuracy?