Re: [Fwd: ProPhotoRGB & Ekta Space]
Re: [Fwd: ProPhotoRGB & Ekta Space]
- Subject: Re: [Fwd: ProPhotoRGB & Ekta Space]
- From: Terry Wyse <email@hidden>
- Date: Tue, 02 Oct 2001 19:57:30 -0400
on 10/2/01 2:29 PM, Robin Myers wrote:
>
The current standard for L*a*b* encoding only covers 8-bit encoding, which
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represents a range of L* (0 min,100 max), a* (-128,127), b* (-128,127) with
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integer steps in a* and b*. To encompass the entire range of L*a*b* values
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that would contain the entire spectral locus would require an encoding range
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of a* (-300,+300) and b* (-200,+200). There are many devices and gamuts, such
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as digital cameras and film that can record information outside the 8-bit
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ranges. Also, the error built into the 8-bit encoding is a maximum of 1.4 dE.
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This is a huge error for achromatic and near-achromatic colors. Therefore, if
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you have a need for high quality color archiving, I suggest you avoid 8-bit
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L*a*b*.
At the risk of showing my ignorance:
So, if I get what your saying, if I have a 16bit LAB file open in Photoshop,
I'm only able to edit it AS IF it's an 8bit file because of the encoding? If
this is so, then the same would be true of a 16bit RGB file since I can only
edit in a range of 0-255 instead of 0-65,535?
If 8bit encoding in LAB is -128,127 (256 steps) when then wouldn't 16bit
encoding be -65536, 65535?
If 8bit encoding is integer steps in a* and b*, why does my Spectrolino
record values to two decimal places?
>
There are many devices and gamuts, such
>
as digital cameras and film that can record information outside the 8-bit
>
ranges.
I'm not sure I get this either. Why would this be true anymore than 0-255
does not define the "range" of color, simply the scale that is used in an
RGB file? Not that I'm challenging any of this, I simply don't understand
it.
Terry