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That is one of the reasons why it’s common for RAW camera formats to be 10 or 12 bits per channel (30 bits or 36 bits per pixel). It’s also common for those working on photos to import RAW to a 16 bit per channel document for further manipulation.

Sometimes. But, often it is not.

The OpenEXR format supports 32 bit float channels. That might sound excessive, but it’s often used for VFX and rendered material, where heavy processing or colour correction may be involved, and large files are less of a concern.

That is one of the reasons why it’s common for RAW camera formats to be 10, 12 or even 14 bits per channel, which works out to be 30, 36 or 42 bits per pixel. It’s also common for those working on photos to import RAW to a 16 bit per channel document for further manipulation. Pro video recording can be 10 bits per channel or higher, too.

Sometimes. But, often it is not.

Please note: I’ve added some more information relating to digijim and Warren Young’s comments below.

“24 bit” usually means 24 bits total per pixel, with 8 bits per channel, or 16,777,216 colours.

“32 bit” also usually means 32 bits total per pixel, and 8 bits per channel, with an additional 8 bit alpha channel that’s used for transparency. 16,777,216 colours again.

Also, 32 bit occasionally means 32 bits per channel (128 bits total per pixel). And, a lot of the time 32 bit per channel uses floating point numbers, rather than integers. I’m happy to add more detail on floating point vs integer, if you’d like.

“16 bit” typically means two different things: 16 bits per pixel or 16 bits per channel. 16 bits total works out to be 65,536 possible colours, and it definitely looks worse than 24 bits total. 16 bits per channel means 281,474,976,710,656 total colours.

I think 8 bit per channel (24 bit per pixel) is on the fringe of what the human eye can easily distinguish, but that’s only part of the story. Processing can cause rounding and clipping, so additional colour depth can push errors beyond the point where humans (and display technology) can see them.

That is one of the reasons why it’s common for RAW camera formats to be 10 or 12 bits per channel (30 bits or 36 bits total). It’s also common for those working on photos to import RAW to a 16 bit per channel document for further processing.

And, in cases where you might not think there’s any processing going on, there might be — colour management can introduce additional processing.

• Using gradients stacked on top of each other, where layers aren’t 100% opacity.
• Gradients drawn without decent dithering.
• Shadows with large blurs.
• Blurred objects.

“24 bit” usually means 24 bits total per pixel, with 8 bits per channel for red, green and blue, or 16,777,216 total colours. This is sometimes referred to as 24 bit RGB.

“32 bit” also usually means 32 bits total per pixel, and 8 bits per channel, with an additional 8 bit alpha channel that’s used for transparency. 16,777,216 colours again. This is sometimes referred to as 32 bit RGBA.

Also, 32 bit occasionally means 32 bits per channel (128 bits total per pixel). And, a lot of the time 32 bit per channel uses floating point numbers, rather than integers. (I’m happy to add more detail on floating point vs integer, if you’d like.)

“16 bit” can typically mean two different things: 16 bits per pixel or 16 bits per channel. 16 bits per pixel works out to be 65,536 possible colours, and it definitely looks worse than 24 bits per pixel. 16 bits per channel means 281,474,976,710,656 total colours — well beyond human perception, but handy for processing.

I think 8 bit per channel (24 bit per pixel) is on the fringe of what the human eye can easily distinguish, but that’s only part of the story. Processing can cause rounding and clipping, so additional colour depth can push errors beyond the point where humans and display technology can see them.

That is one of the reasons why it’s common for RAW camera formats to be 10 or 12 bits per channel (30 bits or 36 bits per pixel). It’s also common for those working on photos to import RAW to a 16 bit per channel document for further manipulation.

And, in cases where you might not think there’s any processing going on, there might be — colour management alone can introduce additional processing.

• Using gradients stacked on top of each other, where layers aren’t 100% opacity.
• Gradients drawn without decent dithering.
• Shadows with large blurs.
• Blurred objects.
• Blending modes and other compositing of two or more layers.

“24 bit” usually means 24 bits total, and 8 bits per channel, or 16,777,216 colours.

“32 bit” also usually means 32 bits total, and 8 bits per channel, with an additional 8 bit alpha channel that’s used for transparency. 16,777,216 colours again.

24 bit and 32 bit can mean the same thing, in terms of possible colours. It’s also worth noting that transparency does’t need to be sent to your display, because displays are opaque (you can’t see through your display to what’s behind it, unless you’re Tony Stark).

“16 bit” typically means two different things. 16 bits total or 16 bits per channel. 16 bits total works out to be 65,536 possible colours, and it definitely looks worse than 24 bits total. 16 bits per channel means 281,474,976,710,656 total colours.

I think 8 bit per channel (24 bit total) is on the fringe of what the human eye can easily distinguish, but that’s only part of the story. Processing can cause rounding and clipping, so additional colour depth can push errors beyond the point where humans (and display technology) can see them.

Also, 32 bit occasionally means 32 bits per channel (128 bits total). And, a lot of the time 32 bit per channel uses floating point numbers, rather than integers. I’m happy to add more detail on floating point vs integer, if you’d like.

24 bit per pixel and 32 bit per pixel

“24 bit” usually means 24 bits total per pixel, with 8 bits per channel, or 16,777,216 colours.

“32 bit” also usually means 32 bits total per pixel, and 8 bits per channel, with an additional 8 bit alpha channel that’s used for transparency. 16,777,216 colours again.

24 bit and 32 bit can mean the same thing, in terms of possible colours. It’s also worth noting that transparency doesn’t need to be sent to your display, because displays are opaque (you can’t see through your display to what’s behind it, unless you’re Tony Stark).

32 bit per channel

Also, 32 bit occasionally means 32 bits per channel (128 bits total per pixel). And, a lot of the time 32 bit per channel uses floating point numbers, rather than integers. I’m happy to add more detail on floating point vs integer, if you’d like.

16 bit per pixel or 16 bit per channel?

“16 bit” typically means two different things: 16 bits per pixel or 16 bits per channel. 16 bits total works out to be 65,536 possible colours, and it definitely looks worse than 24 bits total. 16 bits per channel means 281,474,976,710,656 total colours.

RGB or CMYK?

All the above information assumes you’re working with RGB or RGBA images. If an image is CMYK, it could be 8 bit per channel and 32 bit per pixel, with 8 bits for cyan, magenta, yellow and black channels.

I think 8 bit per channel (24 bit per pixel) is on the fringe of what the human eye can easily distinguish, but that’s only part of the story. Processing can cause rounding and clipping, so additional colour depth can push errors beyond the point where humans (and display technology) can see them.

bpp vs bpc

Now might be a good time to mention the shorthand that’s often used for bits per pixel, bpp and bits per channel, bpc. It’s common to write 32bpp etc when talking about these things, to remove the ambiguity of saying 32 bit.

Dynamic range and gamma

Dynamic range should also be factored in. It’s typical for displays to target sRGB (gamma of 2.2). Wider dynamic range means the number of possible values are stretched further, so more colour resolution is needed.