Canon PSP only prints 8bits/ch on Windows 10.

[Doug Gray]

Even though PSP Says it's printing 16bits per channel on my Pro1000, it is not.

Here's how I found out for sure.

I created a gradient from RGB 230,230,230 to 235,235,235 in Photoshop on a 16 bit image at 600 DPI. Then I printed it three ways w/o color management. These are light gray. After printing I scanned the print as a 48 bit tiff file then increased the contrast in Photoshop by 5x using Curves to bring out the steps.

Attached are the three scans:

a) Using PSP 2.2.3 which indicates in the status that it is using 16 bits/channel.
b) Using the XPS driver, known to be 8 bits in Windows with out a plugin.
c) Using the XPS driver but with the Edit->Settings>User Dither box checked.

As expected for the 8 bit driver, there are 6, distinct grays. However the PSP print also has 6 grays though at shifted locations which indicates different rounding or truncation algorithms. Both are consistent with 8 bit printing.

The third gradient shows the effectiveness of the Dither option when printing 16 bit images. Normal photo images already have more than 1 bit of noise and the noise effectively masks the difference.

Note that 8bit/16bit has no effect on gamut size.

Apparently, only Macs have true 16 bit printer paths.

[Bart_van_der_Wolf]

Even though PSP Says it's printing 16bits per channel on my Pro1000, it is not.

Here's how I found out for sure.
[...]

Hi Doug,

Interesting observation.

Just to make sure though, given that Photoshop works in 15-bit-channel (+ 1) accuracy, I assume that you have verified that the gradient you've created is truly 16-bit/channel. I realize that it shouldn't matter much, but one cannot know how printer drivers react when the least significant bit of a 16-bit integer is not reliable. It might e.g. trigger a bug in the printerdriver code (which on a Mac is part of the OS).

Cheers,
Bart

[Doug Gray]

Hi Doug,

Interesting observation.

Just to make sure though, given that Photoshop works in 15-bit-channel (+ 1) accuracy, I assume that you have verified that the gradient you've created is truly 16-bit/channel. I realize that it shouldn't matter much, but one cannot know how printer drivers react when the least significant bit of a 16-bit integer is not reliable. It might e.g. trigger a bug in the printerdriver code (which on a Mac is part of the OS).

Cheers,
Bart

Yeah Bart. Photoshop does operate with a 15 bits in "16 bit" mode. Not only that but if one creates a true 16 bit gradient in a different app, when it's loaded into Photoshop the LSB is tossed. Not that it matters for our purposes. The differences are less than 0.01 dE in any normal gamma colorspace and under 0.05 dE even in a linear gamma space.

Photoshop does create "16 bit" gradients with the gradient tool even though you can only enter 8 bit values for the stop and start points.

[Bart_van_der_Wolf]

Yeah Bart. Photoshop does operate with a 15 bits in "16 bit" mode. Not only that but if one creates a true 16 bit gradient in a different app, when it's loaded into Photoshop the LSB is tossed. Not that it matters for our purposes. The differences are less than 0.01 dE in any normal gamma colorspace and under 0.05 dE even in a linear gamma space.

That's what we'd expect, QED. Have you tried printing from another application, to reduce the possibility that something unforeseen happens during the hand-off of the print data to the printer-driver?

Cheers,
Bart

[digitaldog]

Apparently, only Macs have true 16 bit printer paths.

That would go towards explaining why several older Epson printers on Mac had the 16-bit check box for the native driver but not under Windows. Not that I ever saw a difference with the check box on or off (and under Mojave, it causes a nasty bug on my 3880).

[Doug Gray]

That would go towards explaining why several older Epson printers on Mac had the 16-bit check box for the native driver but not under Windows. Not that I ever saw a difference with the check box on or off (and under Mojave, it causes a nasty bug on my 3880).

Yeah. Marketing hype. More is better. 16 twice as good as 8. That's what I've always hated about sales and marketing. And newbies are the most susceptible. But even worse is when some feature is touted and, in fact, isn't even enabled.

But I too, have never seen a difference printing anything normal. I can't even see any difference in the above gradients I printed until I scanned them and boosted the contrast.