Re: What color space to use for an image archives
Re: What color space to use for an image archives
- Subject: Re: What color space to use for an image archives
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Mon, 09 Jun 2003 10:08:40 -0500
shAf :o) wrote:
>
"Archiving", senso stricto, implies saving the original data without
>
conversion ... but it does presume you can always convert to anything you
>
want later. Assign the device provile, and archive ... and/or assign a
>
better device profile later.
True, although a device profile for a scanner or digital camera will
typically be large (several hundred K bytes) which may be a problem when
archiving many images. By contrast, a working space profile is only a few
hundred bytes and an Lab image has no profile at all (i.e. its profile size
is zero bytes).
>
A conversion to Lab may suit this purpose, but I personally had trouble
>
with conversion artifacts when I tried doing the same RGB=>Lab conversion
>
(and back) with PS v5.
Also true. 8-bit Lab encoding is generally a coarser sampling space than an
RGB working space. For example, an 8-bit sRGB image containing all possible
colors (16+ million of them), after conversion to Lab, will have about 2
million unique colors. So on the average, every 8 unique sRGB colors get
"squished" into the same Lab color by this conversion (i.e. you've lost one
bit -- now you're down to an effective 7-bit image). This data loss may be
significant for some applications.
--
Bruce J. Lindbloom
email@hidden
http://www.brucelindbloom.com
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