Ok, but if the resolution is the same in a case, color depth and bit depth has the same value.
Well, resolution and bit depth are the two, equally-weighted factors of digital color depth. So, if the value of one of those factors remains constant (resolution, in your case), the color depth will change with the value of the other factor (bit depth, in your case).
Likewise, a 10-bit HD image will have less color depth than a 10-bit 4K image.
Also, an 8-bit 8K image will have more color depth than a 10-bit HD image.
Don't really get the point of binning pixels? The image will still use the same amount of storage? Say if you go from 1080p 8-bit - to binning pixels and 10-bit?
Yes. The "storage" required is essentially the color depth of a digital image.
In film you always talk about bit depth and the image resolution is known, in my world its not wrong as it affect color depth and always get same value if the resolution is the same.
Yes. As acknowledged above, if the resolution remains constant in a digital system, the color depth increases/decreases with a change in bit depth.
However, with actual "film," there is no "bit depth" -- analog film is not digital. So color depth of actual film comes from resolution (grain size) and from dye/emulsion properties (which, in combination, can be considered the analog "equivalent" of bit depth).
But yes this pixelbinning thing is possible, I understand how it affect bitdepth and color depth if you alter resolution, but why use it? Just because its possible?
In any situation in which one is down-scaling an image (such as the common 4K-to-HD conversion), it makes sense to bin the pixels to retain the color depth (and to also reduce noise and to avoid moire/aliasing).
Yes and even if the colordepth is increased?
The color depth of a digital image can never be increased, unless something artificial is added.
If you record your 8-bit signal within a 16-bit file, it won't be better then the original 8-bit/8 bits per channel (color depth).
Yes. The image will not improve merely by putting it into a file/system of a higher bit depth. On the other hand, in doing so you will technically have an image of a higher bit depth.