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Author Topic: 16 Bit Printing  (Read 48034 times)

cybis

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Re: 16 Bit Printing
« Reply #20 on: April 26, 2014, 06:55:23 pm »

A while ago I experimented printing gradients in 16-bit and 8-bit on an Epson 7900. I printed all kind of gradients, some very long. There was exactly zero difference between the two methods. I was really surprised by the results as I certainly expected to see some subtle steps in the 8-bit version. There were absolutely none. My conclusion is that either the driver applies some kind of dithering to 8 bit file or that the intrinsic dithering used by inkjet printers to apply ink droplets makes any difference invisible to the human eye.

For the effect of noise (and I assume also dithering) and bit-depth see:  http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html

There is a measurable different when printing uniformly colored patches but the only scenario where it would matter is when validating icc profiles (not when creating them as the source file is 8-bit).

If anyone knows a method to demonstrate an observable difference in the smoothness of gradients printed in 8-bit vs 16-bit, please share!
« Last Edit: April 26, 2014, 07:00:49 pm by cybis »
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tlester

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Re: 16 Bit Printing
« Reply #21 on: April 27, 2014, 09:52:55 am »

I'm curious if those of you who don't see any difference are printing from JPEG's or anything that was a JPEG in some part of it's image journey.  Clearly if you are printing 8bit images, like a JPEG, you won't see any difference.
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cybis

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Re: 16 Bit Printing
« Reply #22 on: April 27, 2014, 11:19:22 am »

Not printing in jpg. I printed long dither free, noise free, silky smooth gradients. No difference.
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chichornio

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Re: 16 Bit Printing
« Reply #23 on: April 28, 2014, 01:16:50 pm »

A while ago I experimented printing gradients in 16-bit and 8-bit on an Epson 7900. I printed all kind of gradients, some very long. There was exactly zero difference between the two methods. I was really surprised by the results as I certainly expected to see some subtle steps in the 8-bit version. There were absolutely none. My conclusion is that either the driver applies some kind of dithering to 8 bit file or that the intrinsic dithering used by inkjet printers to apply ink droplets makes any difference invisible to the human eye.

For the effect of noise (and I assume also dithering) and bit-depth see:  http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html

There is a measurable different when printing uniformly colored patches but the only scenario where it would matter is when validating icc profiles (not when creating them as the source file is 8-bit).

If anyone knows a method to demonstrate an observable difference in the smoothness of gradients printed in 8-bit vs 16-bit, please share!

As I said in my previous post, using my Hp z3200ps with the EWS and sending a 16 bits tiff file directly to the printer, the difference in very clear for me. As the user manual of the HP3200ps states, the conversion from 16 to 8 bits printing is done inside the printer hardware. No color managment issues if you have the right paper preset and icc profile for the paper selected. Neither is a OS involved in the process.
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cybis

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Re: 16 Bit Printing
« Reply #24 on: April 28, 2014, 01:35:54 pm »

It could be that there is a observable difference between '16bit > 8bit > icc' vs '16bit > icc > 8bit'.
My tests were performed with application and printer driver CSM off.
« Last Edit: April 29, 2014, 01:16:48 am by cybis »
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chichornio

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Re: 16 Bit Printing
« Reply #25 on: April 28, 2014, 11:24:38 pm »

It could be that there is a observable difference between '16bit > 8bit > icc' vs '16bit > icc > 8bit'.
My test were performed with application and printer driver CSM off.

This is what the HP z3200ps user´s manual states:

HP Designjet Z3200PS Printer Series - Print 16-bit color images
Print 16-bit color images

In a 16-bit RGB image, each of the three primary colors is encoded by a 16-bit value, so that each pixel takes up 48 bits.

If you print your 16-bit color images through a printer driver, they will be reduced to 8-bit colors before they reach the printer.

In order to send a 16-bit color image to the printer, you must save it as a 16-bit color TIFF or JPEG file, then send the file directly to the printer without using a printer driver (see Using the Embedded Web Server to print files ). In this case, color management is done on the 16-bit color image, and is therefore done more accurately. The image is still reduced to 8-bit colors for final printing.
Some applications refuse to save a 16-bit color image in JPEG format; others automatically reduce it to 8-bit colors. A TIFF file generally gives a higher-quality result, and is recommended.
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cybis

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Re: 16 Bit Printing
« Reply #26 on: April 29, 2014, 01:42:26 am »

The image is still reduced to 8-bit colors for final printing.

So it seems that no matter what, the HP Z3200 only ever use 8-bit to print. If you let the HP printer (driver) manage colors (uncommon), as opposed to letting the application do the job (more typical), this '16bit > 8bit > icc' could happen, which isn't optimal.

Now what about PS, LR, Qimage? How do these applications actually handle the printer color profile conversion of a 16-bit image before sending it to the printer driver? I assume they perform '16bit > icc > 8bit'? Do Epson and Canon drivers ever actually send 16-bit data to the printer?
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Schewe

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Re: 16 Bit Printing
« Reply #27 on: April 29, 2014, 02:07:24 am »

Now what about PS, LR, Qimage? How do these applications actually handle the printer color profile conversion of a 16-bit image before sending it to the printer driver?

Can't tell you how Qimage does it, but if you are printing a 16 bit image using either Photoshop or Lightroom to manage color AND you use the Adobe ACE CMM, then the application does a color transform from the current color space to the output color space (the printer profile) in 20-bit precision. So, while the print pipeline can only handle 8 bit (except for Epson on the Mac or the Canon export plug-in) that final conversion from the image color space to the printer color space has 20-bit precision before the final 8-bit conversion...

Which is one reason that comparing printing in 16-bit is hard to compare to 8-bit. In essence, on Mac or Windows the print pipeline can already handle the 16-bit to 8-bit in high precision. So, it's hard to prove that printing in 16-bit is superior...

In point of fact, the only time I've ever seen a real advantage is when print long and subtle synthetic gradations...Illustrator or InDesign gradations can show better/smoother gradations when printed using a 16-bit print pipeline.

Personally, I'm pretty much on the fence about image detail in a 16-bit vs 8-bit print pipeline. Since I'm using 16-bit ProPhoto RGB images and printing primarily using Lightroom, I go ahead and print using the 16-bit print option. But, I'm using LR manages color and get the benefit of 20-bit precision anyway...but if I forget and print using the normal Epson 8-bit pipeline, I'm not seeing any substantial differences.

If you are printing 16-bit using an Epson on Mac (or using the Canon export plug-in) you may as well use the 16-bit option. The only downside is slightly slower print spooling times...

But if you are printing on Windows using an Adobe app managing colors, the differences will be so subtle as to be irrelevant.

Yes, it would be useful if both OSs offered 16-bit print pipelines...on Windows Photoshop has the ability to use a 16-bit display pipeline (don't ask me why Apple has failed to offer 16-bit).
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Bart_van_der_Wolf

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Re: 16 Bit Printing
« Reply #28 on: April 29, 2014, 05:53:56 am »

In point of fact, the only time I've ever seen a real advantage is when print long and subtle synthetic gradations...Illustrator or InDesign gradations can show better/smoother gradations when printed using a 16-bit print pipeline.

Hi Jeff,

I think that the conversion from a large gamut colorspace, with relatively large quantization steps per channel, down to a generally much smaller print-medium colorspace, with relatively much smaller quantization steps to cover a smaller possible range, is where the potential damage is occurring. Afterall, ProPhoto RGB is not recommended for an 8-b/ch colorspace when significant image editing is yet to take place, and profile conversion is IMO significant image data manipulation.

It might be interesting to repeat such a gradient print, one with a prior conversion to the output profile in 16-b/ch, then changing the mode to 8-b/ch, and compare that print out to a full bit depth pipeline output.

Of course, dithering in an 8-b/ch profile conversion can attempt to hide some of the problems.

Cheers,
Bart
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digitaldog

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Re: 16 Bit Printing
« Reply #29 on: April 29, 2014, 10:33:31 am »

After two pages, I believe the general answer is, you have to test this with your particular workflow. The OS, print driver, application, color space and more seem to play a role here and there are too many variables. I'd suggest that if you have high bit data, might as well send it to the printer with the hope it's getting there <g>. In a raw workflow, I think most of us will work with high bit data and probably wide gamut data going off to the printer under our control. So if you have options for sending it that way, do so. I would expect that if you do run into differences in color and tone sending 8-bit vs. 16-bit, build the profile with a 16-bit target. Again, my experience is that I can send 8-bit vs. 16-bit data to my Epson's with the same profile but YMMV. It might be interesting for those that have seen these differences to send a patch target through as both 8-bit vs. 16-bit, them measure them so we could plot the differences in something like ColorThink. I'd love to see where in color space these differences are seen.
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cybis

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Re: 16 Bit Printing
« Reply #30 on: April 29, 2014, 01:49:13 pm »

In point of fact, the only time I've ever seen a real advantage is when print long and subtle synthetic gradations...Illustrator or InDesign gradations can show better/smoother gradations when printed using a 16-bit print pipeline.
Jeff, thank you for your informative post. I’m interested in trying to reproduce the results you obtained with the synthetic gradients. I did some test a couple years back with long gradients and saw no difference.
I printed from a Mac to an Epson 7900, all CMS off. Linear gray gradients were created in PS 16-bit with dither off.  I used partial gradients, with different gray level ranges, 23” long @ 360 dpi, no resize.
I haven’t tried illustrator, radial or colored gradients.
Jeff, do you remember what kind of synthetic gradients you used to evaluate smoothness?  It would be neat if there was a image we could all use to evaluate our workflow for smoothness.
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Schewe

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Re: 16 Bit Printing
« Reply #31 on: April 29, 2014, 03:26:07 pm »

Jeff, do you remember what kind of synthetic gradients you used to evaluate smoothness?  It would be neat if there was a image we could all use to evaluate our workflow for smoothness.

All I remember is when we were putting together the Epson Print Academy Track II around the time that the 79/9900 were first introduced and Epson was touting the 16-bit print pipeline, Epson had some Illustrator files that could show a smoother gradation when printed in 16-bit vs 8-bit. Note, as I recall we weren't using the Adobe ACE CMM, I think it was the Apple CMM (which is less precise than ACE). As I recall there were some color gradations and neutral gradations that showed areas where the gradation was a bit blocky in 8-bit vs the 16-bit. I'm pretty sure they were printed from Illustrator.

Sorry I can't any further...and truth be told, the differences seen were subtle. I've never seen any differences when using Photoshop or Lightroom when printing photographic images with grain or sensor noise.
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cybis

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Re: 16 Bit Printing
« Reply #32 on: April 29, 2014, 04:27:21 pm »

Note, as I recall we weren't using the Adobe ACE CMM, I think it was the Apple CMM (which is less precise than ACE). As I recall there were some color gradations and neutral gradations that showed areas where the gradation was a bit blocky in 8-bit vs the 16-bit. I'm pretty sure they were printed from Illustrator.

So it's conceivable that any difference you saw back then was introduced during the color transform performed by the CMM, not purely by the printer using or not using 16-bit data, correct? And if so the benefit of the 16 bit pipeline is independent of the brand and type of printer, OS, etc. The only variables that matter are which CMM does the transform and at what bit depth. (The horse is not quite dead yet  ;D )
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Schewe

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Re: 16 Bit Printing
« Reply #33 on: April 29, 2014, 04:34:40 pm »

Apple CMM has a 16-bit color transform. Adobe ACE (originally done by Thomas Knoll) has 20-bit precision. It also has Black Point Compensation (which may or may not be a real factor, it is, however another potential factor).

But, in the grand scheme of things, I don't think there is a "smoking un" here...YMMV :~)
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Ernst Dinkla

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Re: 16 Bit Printing
« Reply #34 on: April 30, 2014, 06:18:09 am »

Now what about PS, LR, Qimage? How do these applications actually handle the printer color profile conversion of a 16-bit image before sending it to the printer driver? I assume they perform '16bit > icc > 8bit'? Do Epson and Canon drivers ever actually send 16-bit data to the printer?

For Qimage a recent discussion Mike participated in, makes it clear:
http://ddisoftware.com/tech/qimage-ultimate/on-the-subject-of-16-bitchannel-internal-workings/

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cybis

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Re: 16 Bit Printing
« Reply #35 on: April 30, 2014, 03:54:37 pm »

For Qimage a recent discussion Mike participated in, makes it clear:
http://ddisoftware.com/tech/qimage-ultimate/on-the-subject-of-16-bitchannel-internal-workings/

So, Qimage does 16-bit>8-bit>icc. Bummer.
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Bart_van_der_Wolf

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Re: 16 Bit Printing
« Reply #36 on: April 30, 2014, 05:59:32 pm »

So, Qimage does 16-bit>8-bit>icc. Bummer.

Hi,

In practice, there is hardly ever any detectable difference in output quality between 16-bit versus 8-bit pipelines, and if there is, it's only possible to demonstrate in a side by side comparison.

I was especially pleased to learn that that the colorspace conversion is done last, after the creation of new pixels at the native printer driver resolution (and Qimage has some very good resampling algorithms to choose from), and after output sharpening (which is halo free, so can be pushed quite far). That's a lot of data to convert, but it does give the best results because the pixels are finished.

Choosing a better workingspace profile than ProPhoto RGB will also help.

Cheers,
Bart
« Last Edit: May 01, 2014, 03:14:54 am by BartvanderWolf »
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Schewe

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Re: 16 Bit Printing
« Reply #37 on: April 30, 2014, 07:21:30 pm »

Choosing a better workingspace profile than ProPhotoRGB will also help.

Hum, what do you think is a better working space?
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Bart_van_der_Wolf

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Re: 16 Bit Printing
« Reply #38 on: April 30, 2014, 07:46:05 pm »

Hum, what do you think is a better working space?

Hi Jeff,

Smaller gamut than ProPhoto RGB, and large enough for the most demanding output medium.

ProPhoto RGB has relatively large quantization steps due to the large gamut that needs to be covered and then mapped down to a smaller output quantization which leads to potential posterization (different values getting the same resulting value). Also, a gamma of 2.2 provides a better spread of data points throughout the gamut space than the gamma 1.8 of ProPhotoRGB (see BruceLindbloom's analysis of his Beta RGB colorspace). Beta RGB has a 99 percent coding efficiency, ProPhoto RGB 87.3 percent.

Cheers,
Bart
« Last Edit: April 30, 2014, 07:58:10 pm by BartvanderWolf »
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cybis

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Re: 16 Bit Printing
« Reply #39 on: April 30, 2014, 08:37:17 pm »

In practice, there is hardly ever any detectable difference in output quality between 16-bit versus 8-bit pipelines, and if there is, it's only in a side by side comparison.
...
Choosing a better workingspace profile than ProPhoto RGB will also help.

I love Qimage for its sharpening, upsampling, etc. And the OCD in me will eventually recover from the realization that I've been throwing all these bits away for so long.  :o

ProPhoto is currently the only space available in ACR that doesn't clip the gamut of the printer. AFAIK, the quantization steps are small enough in 16-bit. But you are right, it's probably not a good space to be in 8-bit.
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