Digital BW, The Print

* -----Original Message-----
* From: Ernst Dinkla [mailto:E.Dinkla@chello.nl] 
* Sent: Saturday, November 29, 2003 3:17 AM
* To: DigitalBlackandWhiteThePrint@yahoogroups.com
* Subject: Re: [Digital BW] 16 bit printing
* 
* 
* Where are actually the bottlenecks of a 16 bit workflow ?

Ernst,

Prior to Photoshop CS working in 16-bit was very unattractive compared to
8-bit with layers. In CS file sizes really pull down system performance as
layers are added. A file of mind that is a 125MB, 8-bit grayscale with 7
layers has a working file size of 487MB (this is the file size reported by
PS when the file is open). The identical file and layers in 16-bit is 250MB,
as you would expect, but the working file size climbs to 6.6GB! This is not
manageable even on the fastest systems unless you have far more patience
than I do.
* 
* True 16 bit scanning is possible on some scanners meanwhile, 
* the difference with the ones that do a 14 bit A/D conversion 
* will be hardly noticeable. Bitmap editors like PWP and PS now 
* allow full 16 bit editing. At the end of the workflow the 
* printer engine itself will be only available as 8 bit, if it 
* actually produces 255 steps per colour on the paper we will 
* already be very happy and probably we will never notice it 
* when it produces only 230 steps or less. Are there 16 bit 
* printengines ? Lightjets etc ? That it will only show in 
* transparencies is another matter.

I don't think that there is any advantage to sending 16-bit data to the
printer. The only point to working in 16-bit is to ensure that the 8-bit
mode data that arrives at the printer has a full 256 steps. As you correctly
note, we can get away with far less than 256 but at some point, with some
images, you do drop far enough below 256 steps that print quality is
degraded. This may be as low as 100 steps or below. I think the threshold
may vary from person to person so there would seem to be an advantage to
having a large margin for error.

16-bit is overkill. I suspect that for our B&W printing purposes bit modes
of 10 (1024) or 12 (4096) would be more than adequate but  16 will
definitely do the job.

Martin Wesley
http://www.carolyn.cc/Guests/MartinWesley/pages/MW_01.html
http://www.borderless-photos.de/guests.html


* 
* What is more of a question is what printer drivers actually 
* do. The printer drivers usually work with a 16 bit conversion 
* table internally to get better rounding off. That is always 
* used whether it is getting 8 bit or 16 bit channel data as 
* its source. Windows reduces all printerdriver output data to 
* 8 bit when it uses the Windows spooling. There are ways to 
* overcome that but when the printerengines don't take higher 
* than 8 either it has no sense. Gimp-print used 16 bit 
* conversion tables but I really do not know how much 16 bit it 
* is throughout now, no 8 bit filter at the input ?, no 8 bit 
* filter at the output?  Same questions for OS X. I also wonder 
* whether the Epson drivers normally filter the input to 8 bit 
* and only use 16 bit conversion tables internally to drop to 8 
* bit as soon as possible again. Speed is a factor in all that.
* 
* Roy must know the Gimp-print details .............
* 
* Ernst
* 
* 
* 
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