101 – Bit, Byte and Bit Depths

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101 BIT, BYTE and BIT DEPTH

Question:
“What is the difference between a 32 bit TGA and a 32 bit EXR ?”

Answer:
This is not a easy answer if your don’t understand the question.

Knowing the difference will help you talk the lingo and make better choices when producing content.

The following information will allow you to understand, communicate and deliver what is actually being asked for.


What is a “Bit”

The bit is a basic unit of information in information theory, computing, and digital communications. The name is a portmanteau of binary digit. It is either OFF or ON


What is a “Byte”

The byte is a unit of digital information that most commonly consists of 8,16 or 32 bits, representing a binary number. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures.


What is a “Bit Depth"

Color depth (bits per channel)

  • How many bits in each channel.

Bit Depth (bits per pixel)

  • Sum of bits in all your channels.

This becomes an issue as terminology gets used incorrectly many times. This is why using bpc and bpp are important.


What is a “Channel”

In order to create color we need three primary colors RGB. Each of these need a channels to store information. Basic RGB images have 3 channels, some times they have a alpha which increases the channel count to 4.

8 Bit Gray | 1 Channel

Gray - 8 Bits

256 Colors

8 Bit RGB | 3 Channel

Red - 8 Bits
Green - 8 Bits
Blue - 8 Bits

16,777,216 Colors

8 Bit RGBA | 4 Channel

Red - 8 Bits
Green - 8 Bits
Blue - 8 Bits
Alpha - 8 Bits

16,777,216 Colors + 256 Alpha


Gradient Examples

One of the best way to visual describe bit depths is with gradients.

While the difference between 1 and 8 bits is very apparent you visually don’t see much between 8 and 16 bits. Although when dealing with gradient, for example in a sky, 8 bit is not your best choice.


Talking about color

"The traditional 0-256 is gone,  images today are rarely confined to 8 bit"

Because bit depths can change when talking about colors we must use universal scale.

Here is a better way:

  • 0-1 for 3D, Composite, and log work
    • "Can you add 0.25 of red"
  • 0%-100% Photo work
    • "Can you add 25% more red"

 


Question:
“What is the difference between a 32 bit TGA and a 32 bit EXR ?”

Answer: A 32 bit TGA

- TGA is an 8 bit / 32 Bit Depth file

- Each channel ( R, G, B and Alpha) contains a 8 bit or 256 shades of color.

- Channel bit depth adds up to 32 bit (24 if there is not a alpha).

- A total possible colors is 16.78 Million.

Answer: A 32 bit EXR

- EXR is an 32 bit / 128 Bit Depth file

- Each channel ( R, G, B and Alpha) contains a 32 bit or 4,294,967,296 shades of color.

- Channel bit depth adds up to 128 bit.

- A total possible colors is 80 Octillion.

Common Formats

Bit’s Possible tonal/bit values Bit Depth Possible RGB colors Supported Files Best use as
1 bit 2 1 2 (black or white) n/a Black or white
2 bit 4 2 4 n/a n/a
4 bit 16 16 4,098
bmp
bmp Windows Programs
8 bit (6 bit + FRC)  256 18 16.78 Million 34UM67-P Monitor Monitor
8 bit 256 24 16.78 Million jpeg, gif,
tga
Web, Textures, Games
8 bit (w/ Alpha) 256 32 16.78 Million tga
, png
Web, Textures, Games
10 bit (8 bit + FRC) 1,024 30  1,07 Billion Dell p2415q Monitor Monitor
10 bit 1,024 40 1.07 Billion DPX , CIN

Eizo CG248 Monitor

Film, Color Grading
12 bit 4,095 48 68.68 Billion RAW Photography, TV Productions
14 bit 16,384 56 4.39 Trillion Nikon
RAW
Photography
16 bit 65,532 64 281 Trillion PSD,
PNG, TIFF
Print Images, Professional Photo
32 bit
32 bit 4,294,967,296 128 80 Octillion colors EXR, HDR 3D, HDR & Compositing
  • Frame rate control (FRC) is a method for achieving higher color quality in low color resolution display panels