Digital BW, The Print

When printing a 16 bit file does the printer convert it to 8 bit?  
I've been trying to get the author of Qimage to allow processing of 
16 bit grayscale files.  Qimage has a feature called "print to file"  
where you don't send the file to the printer but to another 
location.  It's a great feature but it takes a grayscale 16 bit file 
and converts it to 8 bit RGB.  Anyway, Mike Chaney has responded with 
the following, "I'd also have to question why you'd want to print 16 
bits/channel when printing to file because printers cannot accept 
anything but 8 bit data (even when using a RIP). As far as I know, 
and unless things have changed recently, all printers (the hardware 
itself) are based on 8 bits/channel even when dealing with grayscale."

I was thinking that it might happen when using the Roark curves and 
the Epson drivers but how about using QTR?

Thanks,

Tom

97.3% sure all printers (Epson etc) use 8 bits max.  Would be a waste to use 16 bit 
considering the dynamic range of paper and ink.  

I often edit in 16 bit, but convert to 8 for printing and for saving (of flattened print files).

Scott

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Tom Husband" <thusband@s...> 
wrote:

> When printing a 16 bit file does the printer convert it to 8 bit?  
> I've been trying to get the author of Qimage to allow processing of 
> 16 bit grayscale files.  Qimage has a feature called "print to file"  
> where you don't send the file to the printer but to another

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Scott Graham" 
<gebilwil@n...> wrote:
> 97.3% sure all printers (Epson etc) use 8 bits max.  Would be a 
waste to use 16 bit 
> considering the dynamic range of paper and ink.  
> 
> I often edit in 16 bit, but convert to 8 for printing and for 
saving (of flattened print files).
> 
> Scott

Right.  I would agree with 8 bit on the Epson driver but I'm not sure 
about using QTR.

Tom

You original question said "printer" not driver. To get the answer 
to this you need to be precise and remember what you asked.

It is quite difficult for a printer to represent 255 shades of grey 
let alone anything more. Most cannot get to 255 shades of grey. 
Hence 8 bit at the printer is fine and what is usual.

However because of all the layers of software in a driver or a RIP 
(that might include a CMM and serious ICC transforms) there is 
reason to use more than 255 so that the first limitation that occurs 
is that of the printer itself and other rounding errors in the 
software do not dominate.

As I recall the Windows driver and the Mac driver too are (or were) 
limited to 8 bits. This is potentially a limitation whereas 8bits at 
the printer is not.

...John 

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Tom Husband" 
<thusband@s...> wrote:
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Scott 
Graham" 
> <gebilwil@n...> wrote:
> > 97.3% sure all printers (Epson etc) use 8 bits max.  Would be a 
> waste to use 16 bit 
> > considering the dynamic range of paper and ink.  
> > 
> > I often edit in 16 bit, but convert to 8 for printing and for 
> saving (of flattened print files).
> > 
> > Scott
> 
> Right.  I would agree with 8 bit on the Epson driver but I'm not 
sure 

> about using QTR.
> 
> Tom

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "johnglodge" 
<john.lodge@s...> wrote:
> You original question said "printer" not driver. To get the answer 
> to this you need to be precise and remember what you asked.
> 
> It is quite difficult for a printer to represent 255 shades of grey 
> let alone anything more. Most cannot get to 255 shades of grey. 
> Hence 8 bit at the printer is fine and what is usual.
> 
> However because of all the layers of software in a driver or a RIP 
> (that might include a CMM and serious ICC transforms) there is 
> reason to use more than 255 so that the first limitation that 
occurs 
> is that of the printer itself and other rounding errors in the 
> software do not dominate.
> 
> As I recall the Windows driver and the Mac driver too are (or were) 
> limited to 8 bits. This is potentially a limitation whereas 8bits 
at 
> the printer is not.
> 
> ...John 

OK, I think I understand.  Thanks and sorry for not being more 
precise.

Tom

> From: Tom Husband [mailto:thusband@...]
>
> When printing a 16 bit file does the printer convert it to 8 bit?
> I've been trying to get the author of Qimage to allow processing of
> 16 bit grayscale files.  Qimage has a feature called "print to file"
> where you don't send the file to the printer but to another
> location.  It's a great feature but it takes a grayscale 16 bit file
> and converts it to 8 bit RGB.  Anyway, Mike Chaney has responded with
> the following, "I'd also have to question why you'd want to print 16
> bits/channel when printing to file because printers cannot accept
> anything but 8 bit data (even when using a RIP). As far as I know,
> and unless things have changed recently, all printers (the hardware
> itself) are based on 8 bits/channel even when dealing with grayscale."
>
> I was thinking that it might happen when using the Roark curves and
> the Epson drivers but how about using QTR?

What goes across the cable to the printer (at least for Epson) is dots, not
8-bit or 16-bit data. Standard printer drivers convert the image to dot
patterns, but only accept 8-bit data. Alternative software, like a RIP,
could in theory use all 16 bits, but I couldn't tell you if QTR does. For
B&W, it's possible that an extra bit or two might be useful on some media,
but it's doubtful that you'd see the difference for color.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul D. DeRocco" 
<pderocco@i...> wrote:
> > From: Tom Husband [mailto:thusband@s...]
> >
> > When printing a 16 bit file does the printer convert it to 8 bit?
> > I've been trying to get the author of Qimage to allow processing of
> > 16 bit grayscale files.  Qimage has a feature called "print to file"
> > where you don't send the file to the printer but to another
> > location.  It's a great feature but it takes a grayscale 16 bit file
> > and converts it to 8 bit RGB.  Anyway, Mike Chaney has responded with
> > the following, "I'd also have to question why you'd want to print 16
> > bits/channel when printing to file because printers cannot accept
> > anything but 8 bit data (even when using a RIP). As far as I know,
> > and unless things have changed recently, all printers (the hardware
> > itself) are based on 8 bits/channel even when dealing with grayscale."
> >
> > I was thinking that it might happen when using the Roark curves and
> > the Epson drivers but how about using QTR?
> 
> What goes across the cable to the printer (at least for Epson) is dots, not
> 8-bit or 16-bit data. Standard printer drivers convert the image to dot
> patterns, but only accept 8-bit data. Alternative software, like a RIP,
> could in theory use all 16 bits, but I couldn't tell you if QTR does. For
> B&W, it's possible that an extra bit or two might be useful on some media,
> but it's doubtful that you'd see the difference for color.
> 
> --
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@i...

Both Mac and PC print systems are based on 8 bit pixel data.  So everything
that gets sent through print commands will be truncated to 8bit pixels.

I would doubt this makes any visible difference -- our eyes just can't
distinguish even 256 grays on paper.  I also think all the conversion to
printer dots is the limiting factor by far.  Another thing to consider is that
smooth areas of an image have lots of pixels and what you see is a blend
of adjacent pixels not individual pixels -- a result of dithering, ink bleed,
and eye resolution.

Roy

Thanks all, I understand this better now.  

Still, 8 bit grayscale grayscale capability in Qimage would be nice.

Tom

To be somewhat sloppy, 256 levels needs a 16x16 array of dots. Of 
course that is not quite true some printers emit more than one dot 
density from the jet. As well dot gain changes the result. So that 
on face value at 2880 the number of halftone patches is 180 per inch 
well except that the other dimension is not 2880. 

If you look at the NCA greyscale for the 2200 there is a flat toe of 
about 45 steps which suggests Epson is getting about 210 distinct 
ink patterns and probably less. In fact I think it has to be quite a 
bit less as the numbers do not compute or there are rather more jet 
harmonics than I thought.

So that at the level of the printer itself 8bits is by far enough. 
Even photoffset printers which were lith, ran at 2450dpi to get good 
150 (I guess I will say lines)per inch quality greyscale prints.

...John

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Roy 
Harrington" <roy@h...> wrote:
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul D. 
DeRocco" 
> <pderocco@i...> wrote:
> > > From: Tom Husband [mailto:thusband@s...]
> > >
> > > When printing a 16 bit file does the printer convert it to 8 
bit?
> > > I've been trying to get the author of Qimage to allow 
processing of
> > > 16 bit grayscale files.  Qimage has a feature called "print to 
file"
> > > where you don't send the file to the printer but to another
> > > location.  It's a great feature but it takes a grayscale 16 
bit file
> > > and converts it to 8 bit RGB.  Anyway, Mike Chaney has 
responded with
> > > the following, "I'd also have to question why you'd want to 
print 16
> > > bits/channel when printing to file because printers cannot 
accept
> > > anything but 8 bit data (even when using a RIP). As far as I 
know,
> > > and unless things have changed recently, all printers (the 
hardware
> > > itself) are based on 8 bits/channel even when dealing with 
grayscale."
> > >
> > > I was thinking that it might happen when using the Roark 
curves and
> > > the Epson drivers but how about using QTR?
> > 
> > What goes across the cable to the printer (at least for Epson) 
is dots, not
> > 8-bit or 16-bit data. Standard printer drivers convert the image 
to dot
> > patterns, but only accept 8-bit data. Alternative software, like 
a RIP,
> > could in theory use all 16 bits, but I couldn't tell you if QTR 
does. For
> > B&W, it's possible that an extra bit or two might be useful on 
some media,
> > but it's doubtful that you'd see the difference for color.
> > 
> > --
> > 
> > Ciao,               Paul D. DeRocco
> > Paul                mailto:pderocco@i...
> 
> Both Mac and PC print systems are based on 8 bit pixel data.  So 
everything
> that gets sent through print commands will be truncated to 8bit 
pixels.
> 
> I would doubt this makes any visible difference -- our eyes just 
can't
> distinguish even 256 grays on paper.  I also think all the 
conversion to
> printer dots is the limiting factor by far.  Another thing to 
consider is that
> smooth areas of an image have lots of pixels and what you see is a 
blend
> of adjacent pixels not individual pixels -- a result of dithering, 
ink bleed,

> and eye resolution.
> 
> Roy

I second that, would be great for resizing prints to send to QTR or some
other B&W print setup.

 

Brad

 

  _____  

From: Tom Husband [mailto:thusband@...] 
Sent: Friday, September 03, 2004 12:38 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Do Printers Only Accept 8 Bit Files?

 

Thanks all, I understand this better now.  

Still, 8 bit grayscale grayscale capability in Qimage would be nice.

Tom



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