[ELI5] Why can’t we access the whole colour gamut they show on the graph? And only portions like sRGB?

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So, I’ve recently started to learn about Display technologies, and I’m having countless questions.
How are able to use 8-bit per channel displays and not run out of system memory?
There must some amount of compression right? Where can I download a true 24 bit image with 1 bit colour occupying 1 bit memory?

In: Technology

8 bit per channel means 3 bytes per pixel or 3 megabytes per 1024×1024 uncompressed image (or 6 megabytes per 1920×1080 fullscreen image) which isn’t that much. Bmp files usually store data like that (some lossless compression may be possible but not always used). Jpg/png/gif use compression, all video is even more compressed.

Also, there are HDR image formats such as .tiff which use even more bits per channel.

Simple answer, math and the lack of any device currently available that can even reproduce the colors. The more colors defined in the gamut the more powerful the device required to calculate and reproduce the colors. Technology hasn’t reached that point and may not ever. We’re talking about basically infinite amount of colors that can be defined by many different parameters(hue, saturation, luminance, etc). It may also be because of diminishing returns. The currently available color space standards are sufficient enough to reproduce most images with good accuracy.

> How are able to use 8-bit per channel displays and not run out of system memory?

A display is 1920 x 1080 pixels. Three color channels at 8 bits per channel gives a total of 49,766,400 bits for the pixels of a full-screen image. Memory is usually counted in bytes, so divide that by 8, and you get 6,220,800 bytes, or about 6 megabytes.

A typical modern system has gigabytes (i.e., thousands of megabytes) of RAM. Six megabytes is nothing, unless you’re talking about decades-old computers.

> There must some amount of compression right?

All the most popular image formats (PNG, JPG) have compression.

> Where can I download a true 24 bit image with 1 bit colour occupying 1 bit memory?

Do you mean a raw image? I suggest investigating the BMP (bitmap) file format, see the Wikipedia article [here](https://en.wikipedia.org/wiki/BMP_file_format). BMP is an uncompressed image file format used by early versions of Windows. Some software still supports it. Check to see if your favorite image editing software can save images as BMP. Note, in addition to the image data itself, BMP has a header that has some information about the image.