Monitor

A monitor is this piece of glass looking thing that you are reading this text. Monitors are like high resolution televisions. Just like your TV, you may need to adjust the brightness or contrast controls in order to full see details in shadows or in bright areas of an image. Some images are washed out or lack enough exposure in the shadows to show details, but if others can see what you cannot, it is either a cheap monitor or the adjustment settings on it.

You should be able to distinguish between all sixteen tones of gray below, but not everyone will see the differences in the second row of 32 grays:

In the typical color space, we can talk about 256 different tones of pure grays (or any color). At some point the individual eye cannot distinguish between those colors, and the typical monitor will fail to produce the shade perfectly. Adjusting brightness and contrast won't change that. You'll need to get the red, green, blue lights aligned perfectly to keep each shade unique. Some monitors will simply not be able to do this over the entire screen area.