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.


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"

 


Now you should know why we need to know this.

 

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

Answer:

A 32 bit TGA is:

  • TGA is an 8 bit / 32 Bit Depth file

  • Each channel ( Red, Green, Blue 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.

A 32 bit EXR is:

  • EXR is an 32 bit / 128 Bit Depth file

  • Each channel ( Red, Green, Blue 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’sPossible tonal/bit valuesBit DepthPossible RGB colorsSupported FilesBest use as
1 bit212 (black or white)n/aBlack or white
2 bit424n/an/a
4 bit16164,098
bmp
bmpWindows Programs
8 bit2562416.78 Millionjpeg, gif,
tga
Web, Textures, Games
8 bit (w/ Alpha)2563216.78 Milliontga
, png
Web, Textures, Games
10 bit1,024401.07 BillionDPX , CINFilm, Color Grading
12 bit4,0954868.68 BillionRAWPhotography, TV Productions
14 bit16,384564.39 TrillionNikon
RAW
Photography
16 bit65,53264281 TrillionPSD,
PNG, TIFF
Print Images, Professional Photo
32 bit
32 bit4,294,967,29612880 Octillion colorsEXR, HDR3D, HDR & Compositing