Bit Depths

You are here:
< Back to Wiki
8 bit terminology problem

(the Photoshop 255 color picker)

8 Bit color picker

32 bit color picker
The reason we use the 0-255 color scale is because of 8 bit images. For a long time an artist could only give a pixel 256 tones of the three primary colors.

With 8 bit technology becoming less used the 0-1 (0% to 100%) value system is starting to become the norm. This scale isn’t dependent on a bit format as 8 or 32 bit can all share the same percent value. Only the increments inbetween the (Bit Depth) are different.

 

 

 

 

 

 

 Bit’s Possible tonal values Possible RGB colors Bit Depth Supported Files
1 bit 2 2 (black or white) 1 Bit Depth
2 bit 4 4 2 Bit Depth
4 bit 16 4,098 16 Bit Depth Bmp
8 bit 256 16.78 Million 24 Bit Depth Jpeg, Gif
8 bit (with an alpha) 256 16.78 Million 32 Bit Depth TGA
10 bit 1,024 1.07 Billion 40 Bit Depth DPX , CIN
12 bit 4,095 68.68 Billion 48 Bit Depth RAW
14  bit 16,384 4.39 Trillion 56 Bit Depth Nikon  RAW
16 bit 65,532 281 Trillion 64 Bit Depth PSD, PNG, TIFF
32 bit 4,294,967,296 80 Octillion colors 128 Bit Depth EXR

 

Bit (byte)

A collection of values

One 1 bit can store 2 values 2 tones of Red.
One 2 bit can store 4 values 4 tones of Red.
One 4 bit can store 16 values 16 tones of Red.
One 8 bit can store 256 values 256 tones of Red.
One 16 bit can store 65,532 values 65,532 tones of Green.
One 32 bit can store 4,294,967,296 values 4,294,967,296 tones of Blue.

 

Bit Depth

The sum of all bits colors per channel  to make a pixel color/value

Example of bit depth options
Example of bit depth options

How many Bit (byte) can fit into each Bit Depth

Three 8 bits ( 255 Red, 127 Green and 10 Blue ) creates a 24 bit depth file.
Four 8 bits ( 255 Red, 127 Green, 10 Blue and 50% Alpha) creates a 32 bit depth file.
Three 32 bits ( 0.75 Red, 0.25 Green and .10 Blue ) creates a 128 bit depth file.

Channels

Colors/values per channel/File

Channels in Nuke (1,023 max)

Channels in Photoshop

How many Bit Depth can go into one Channel/File

Some file formats only use RGB other use RGBA. Rarely do image files have more that 4 colors/values.

Jpeg only allows 3 bits per pixel [ Red  Green Blue ].

TGA allows 4 bits per pixel [ Red  Green Blue Alpha].

PSD sorta allows 5 bits per pixel [ Red  Green Blue Alpha Transparency].