Re: Decent results with Gutenprint - the poor man's RIP.
Re: Decent results with Gutenprint - the poor man's RIP.
- Subject: Re: Decent results with Gutenprint - the poor man's RIP.
- From: Roy Harrington <email@hidden>
- Date: Tue, 20 Jun 2006 08:36:22 -0700
On Monday, June 19, 2006, at 12:03 AM, Kai-Uwe Behrmann wrote:
Am 18.06.06, 01:27 -0400 schrieb Robert L Krawitz:
That's fine, as long as your application supports it (most Linux/UNIX
apps don't), and as long as the data path is 16 bits/channel. If the
path is 8 bits/channel, and you're doing color management in the
application, you're losing a lot of information. Color management
basically performs a mapping; if the output space is 8 bits/channel,
and the mapping isn't 1-1 (which normally it won't be), you might wind
up with stair stepping.
I would say 8-bit causes allways stepping to some motives. Fog, smoke,
blue sky and even surfaces covering larger image areas are very
sensible
to stepping. Digital imagery with its eventone characteristic, in
opposite
to more or less grainy 36mm film, can make this evident. I see
Gutenprint's 16-bit paths serves very well for sensible digital
photographs in regards of non stepping.
regards
Kai-Uwe Behrmann
The 8-bit vs 16-bit debate always seems to bring out a lot of
discussion.
The one aspect that I think tends to be ignored is that images contain
lots of pixels and our perception of them invariably is based on
averaging
and blending of adjacent pixels (or on inkjet printers on adjacent
dots).
So while 8-bit seems to imply 256 distinct grays (or each color) in fact
an 8 bit file can easily show many more shades -- whether you are
looking
with your eye or using an accurate spectrophotometer.
For example you can easily show a value between 127 and 128 by just
alternating pixels i.e. dithering for any intermediate value. This
method of
representing intermediate values is used in Photoshop when converting
16-bit to 8-bit and in the Color Management when producing 8-bit data
on profile conversion.
Another thing to consider is that ICC profiles the CLUT tables are
typically
25x25x25 points for RGB. The values at each point are 16-bit but all
the
intermediate points are calculated by simple linear interpolation. So
non-
linearities are a much more serious issue regardless of 8 or 16 bit
output.
I think linearizing the print driver response would be a more important
factor than having a 16-bit interface.
Roy
-
Roy Harrington
email@hidden
Black & White Photo Gallery
http://www.harrington.com
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