8-bit grayscale to duotone

S
Posted By
steven
Nov 13, 2004
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414
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2
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Closed
Scanned a B&W negative as color, converted to 16-bit grayscale. Image has 20745 levels* of gray.
If I want to have this printed as duotone I can get a maximum of 2500 levels. Or rather, could.
‘coz Photoshop wants me to convert to 8-bit grayscale first, for 256 levels of gray. That’s 10% of what duotone can handle.
Or am I missing something?

* counted using Gregory Paret’s Color Counter
(http://www.users.cloud9.net/%7Egparet/photoshop/#counter). Thanks Greg. (The postcard is on its way)
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bit duotone grayscale

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F
Fixx
Nov 14, 2004
In article <d4tld.21689$>,
"steven" wrote:

Scanned a B&W negative as color, converted to 16-bit grayscale. Image has 20745 levels* of gray.
If I want to have this printed as duotone I can get a maximum of 2500 levels. Or rather, could.
‘coz Photoshop wants me to convert to 8-bit grayscale first, for 256 levels of gray. That’s 10% of what duotone can handle.
Or am I missing something?

Where did you get that 2500 levels information? I think printed piece cannot contain that many levels in practice any case, regardless printing method. Duotone does not add any "levels", it just "patches" printing problems by adding second lighter ink to make distinguishing the lighter levels easier. -F
S
steven
Nov 14, 2004
"Fixx" wrote in message
In article <d4tld.21689$>,
"steven" wrote:

Scanned a B&W negative as color, converted to 16-bit grayscale. Image
has
20745 levels* of gray.
If I want to have this printed as duotone I can get a maximum of 2500 levels. Or rather, could.
‘coz Photoshop wants me to convert to 8-bit grayscale first, for 256
levels
of gray. That’s 10% of what duotone can handle.
Or am I missing something?

Where did you get that 2500 levels information? I think printed piece cannot contain that many levels in practice any case, regardless printing method. Duotone does not add any "levels", it just "patches" printing problems by adding second lighter ink to make distinguishing the lighter levels easier. -F

From the Photoshop help files: "a printing press can reproduce only about 50 levels of gray per ink "
So using 2 inks would give a maximum of 50×50, thogh probably less because different combinations will result in the same print color/tone. About distinguishing the lighter levels: how can you distinguish between levels which aren’t there anymore? Converting to 8-bit removed 99% of the levels the image had. 🙁

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