8, 16, 24 bit? I’m confused again

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Posted By
Billbone
Jul 16, 2003
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289
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2
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I do beginner design for web and ink jet printers, but I wanted to send something to a magazine.

They asked for a 24 bit file, which my file can scan at.

Why is it that Photoshop only has 8 or 16 bit to choose from? Clearly I’m missing something, can someone help me understand?
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Tom Thackrey
Jul 17, 2003
On 16-Jul-2003, Billbone wrote:

I do beginner design for web and ink jet printers, but I wanted to send something to a magazine.

They asked for a 24 bit file, which my file can scan at.
Why is it that Photoshop only has 8 or 16 bit to choose from? Clearly I’m missing something, can someone help me understand?

You are confusing bits per pixel with bits per color. Photoshop is talking about bits per color.
8 bits per color, 3 colors = 24 bits per pixel
16 bits per color, 3 colors = 48 bits per pixel

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Tom Thackrey
www.creative-light.com
M
Mpaintnz
Jul 17, 2003
"Billbone" wrote in message
I do beginner design for web and ink jet printers, but I wanted to send something to a magazine.

They asked for a 24 bit file, which my file can scan at.
Why is it that Photoshop only has 8 or 16 bit to choose from? Clearly I’m missing something, can someone help me understand?

Finished files count the total number of bits as one value. Photoshop counts the number of channels and the bits per channel as two separate values.

The maths are easy enough, multiply the channel by the bits per channel when you save.

e.g
A three channel RGB photo in PS at 8bits per channel would save as a 24bit file.
A three channel RGB photo in PS at 16bits per channel would give you a 48bit file.
A four channel CMYK file in PS at 8bits per channel would give you a 32bit file.
etc…

So if they are asking for a 24bit file, they sound to me like they want a RGB (8bit per channel) jpeg/tiff .

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