101 – Bit, Byte and Bit Depths

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"

When referring to a pixel, the concept can be
defined as

  • Bit Depth
  • Color Depth
  • Resolution of Bits/Pixel
  • Bits per pixel

All of these specifies the number of bits used to
create that color.

Targa format supports 16 bit depth RGB images (5 bits x 3
color channels, plus one unused bit) . The file will no longer be
in 8 bit but 5bit Adobe Photoshop Reference.


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 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 1,024 40 1.07 Billion DPX , CIN 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
Mike Oakely

Mike Oakely

Mike Oakley is a seasoned and passionate freelance visual effects artist in Seattle, Wa. He is a true generalist. Animations, material creations, FX, composting, editing, audio are all skills he enjoys working with. In 2013 he won a Emmy for Outstanding Special Visual Effects in a Supporting Role for the episodic "Banshee". His energetic attitude, strong work ethic and creative insight assures projects are completed on time and exceed expectations. He enjoys changing of hats on a project to fill in gaps on a production.