Digital BW, The Print

Now that this has gone round and round several times.

1. 8 bit integer (which is what we are talking about) is quite coarse
in accuracy down at low values. 16 bit is a lot better and in the
print driver or RIP a profile is applied so that the same conditions
apply as in an image file being opened in PS or any other color
managed application. With 8 bit: funnies accumulate, with 16 bit:
there is more latitude.

2. When the printer is stripped back (with Epson piezo printers) to
the basics the ink onto paper process is not the function of a
continuous variable. In the combination of halftoning, dotgain, the
size of the ink drops that can be emitted: and even the total internal
reflection (of light) in the paper surface (particularly if it is
gloss) lead to a complex situation that may not be monotonic across
the spce of enumerated patterns and certainly is not a continuous
variable.

It is goodness for the software to be implemented in 16 bit: (all the
way) for both profiles and for the image files. This leaves only the
irregularity of the actual ink deposition process to have oddities.

There are most likely less than 256 effective levels in density scale
but it will take 16 bit software to fully exploit them and it will
take subtle profiling software to deal with the lack of monotonicity.

Taking the information that because there is likely less than 256
levels in the density and using it to suggest that only 8 bit software
is needed is the same argument that we are moving away from with the
image processing software. If there are multiple steps with rounding
errors, the resultant output will not be 8 significant bits with will
be more like 6 or 5. (The legendary rule of not going in and out of
Lab space in PS is of the same ilk, with 8 bit numbers the errors
build too fast).

The same situation exists with LCD displays. IF you look at the
information on the details of the excellent Eizo displays they have
(at least those meant for quality work) a 10bit internal LUT. That is
there are 256 entries in the LUT, but the table entries are 10bits
wide as is the DAC in the display. This is used for the same reasons
as for printers etc; the basic LCD response is sufficiently irregular
to need information to express the voltages needed. Even though only 
     
8bit changes in brightness are being expressed.

...have a good day all!  

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, José Miguel
Ferreira <jmf@j...> wrote:
> Hi,
> 
> If I understand correctly, the advantages of working in 16 bit mode
are more
> relevant during the editing of the image in PS. I can't remember where I
> read it (might have been Dan Burkholder's digital negative book) but
there's
> an awful lot of pixel twisting and bending that will normally
degrade the
> image quality as you edit along. Having the files in 16 bit mode
(more data
> = more flexibility) helps keep the image well-preserved. But once
all the
> editing has been done, (with layers, always) I'm not so sure it
matters so
> much. I could be wrong...
> 
> José
> 
> -----Original Message-----
> From: Tyler Boley [mailto:tyler@t...] 
> Sent: vendredi, 14. janvier 2005 17:26
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: [Digital BW] Tyler's comments Re: 16 bit and printer output
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "john dean"
> <deanwork2003@y...> wrote:
> ...
> > So, no one has convinced me yet that the work flow of working with a
> file size that is twice 
> > what is needed to output ( and store on a cd or dvd ) is worth this
> trouble.
> 
> John, for me it's no trouble. Single channel files are still not that
> big in hi bit, and storage gets cheaper and cheaper.
> Rather than do a slurry of testing that may show different results
> with different images hence a multitude of qualifiers to track down,
> I'd rather just stay in hi bit the whole way.
> Besides, the files may need further editing some day for different
> output or whims.
> Long ago, testing with a different RIP, I did see a difference,
> sometimes. Since the RIP I use accepts hi bit in, I'll just stick with
> it to make sure I'm getting the best possible for now.
> It's working, and at some point it's more satisfying to make prints
> than tests.
> Tyler
> 
> 
> 
> 
> 
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