’BIT DEPTH’ AND ‘BIT SIZE’
A ‘bit’ is a computer term for data storage. It can only contain two values, typically 0 or 1. 8-bit simply means the data chunk is 8 bits in total (or 2 to the power of 8, as each bit can be either ‘1’ or ‘0’). This allows for numeric values ranging from 0 to 255.
Similarly 16-bit means the data size is 16 bits in total. (or 2 to the power of 16) This allows for numeric values ranging from 0 to 65535.
Sidenote: Photoshop does not seem to be using the full range of those 16-bits. If you look at the built in information panel it allows you to swap to 16-bit view and it then shows 0-32768 values. Meaning it would in fact be 15-bits +1. For the purpose of this article this is not that big of a deal though, so I am going to show the difference to 16-bits to keep things simple.
To give you a general idea, a comparison 16 bits can contain 256 times more numerical values then 8 bits. If you were to put it on a graph, this is what it would look like:
BITS PER PIXEL
Bits per channel are pretty easy to understand, it is the number of bit used to represent one of the color channels (Red, Green, Blue). But to complicate things the ‘bit depth’ setting when editing images, specifies the number of bits used for each color channel – bits per channel (BPC).
This means that the 8-bit setting (BPC) is in fact 24-bits per pixel (BPP). Meaning that each pixel can have values ranging from 0 to 16,777,215, representing about 16 million colors.
As the human eye can only discern about 10 million different colors, this sounds like a lot. But if you consider that a neutral (single color) gradient can only have 256 different values, you will quickly understand why similar tones in an 8-bit image can cause artifacts. Those artifacts are called posterization.
Similarly the 16-bit setting (BPC) would result in 48-bits per pixel (BPP). The available number of pixel values here is mind boggling (2^48). More than 16 million times more numerical values then the 8-bit setting. Again, this may seem like an overkill, but if you consider the neutral color gradient again, the maximum amount of tonal values is ‘only’ 65,536.
Note: Photoshop will often show a color value between 0 to 255 per channel regardless of what bit depth you edit in. This is purely to simplify things for the user. Behind the scenes it utilizes the full value range. So, pure green, for example, in 8-bit is {0,255,0} and in 16-bit it is {0,32768,0}.
The difference between 8-bit & 16-bit control for LED strip light
What is 8 bit and 16 bit, in the context of LED strip lights and dimming?
When LED strip lights are controlled using a LED receiver (such as as DMX receiver), they are programmed to dim from maximum to minimum levels of brightness/colour/etc in 255 steps. This the standard for what is called 8-bit control.
16-bit LED receivers provide not only the standard 255 steps of control, but also another 255 steps in between those. This gives a total of 512 steps (0-511) of control. The extra precision and granularity gives smoother dimming and colour mixing effects, due to the higher amount of steps.
Which is the best for my project?
For most LED products, 8-bit dimming is the standard, and to the untrained eye this is totally acceptable and looks more than satisfactory. You won’t need 16-bit control unless specifically requested by a professional, such as a theatre manager.
In theatres, for example, when low-level dimming is often required, the final brightness level can appear too much of a ‘step’ to an audience. So it is common for the theatrical industry to require 16-bit dimming, in order to provide the smoothest dimming / mixing possible and obtain the lowest dimming levels before switching off completely.
