How to test if a print was made at 16 bit?

[Doug Gray]

…
 now my worksheet give me a 0.51 DE2000 for these 2 RGB triplets (100.100.100) and (100,100.5,100). This would suggest we are able to discern more then the 256 tones of an 8 bit print.Thanks,
...
YG

Check your calculations. dE00 for those triplets is 0.15, not .51.

Further, Lab=(100,100.5,100) is not even possible on a perfectly reflective print. Even theoretically, as it requires spectral reflectance to exceed 100% at one or more wavelengths.

Let's look just at neutrals. The  dE00 over the neutrals from L*=0 to 100 for unit changes in L* is maximum at L*=50 where it exactly matches deltaE1976 which is 1.0 and decreases on either side of L*=50.

There are only about 72 (IIRC) JND's from L*=0 to 100 based on delta E 2000.

[Doug Gray]

Banding from 8 bit drivers can easily be demonstrated.

Simplest way to demonstrate banding in 8 bit printer drivers, as well as how well 16 bit ones perform is to print the attached gradient without color management (direct to the printer driver just as one would print patches for profiling).

Print the very dark strip, Cut off the white borders. Hold it up to a bright light. You will see the banding from 8 bit drivers and less from 16 bit ones but will likely see some there as well since printers have to convert the image to a printed dot pattern.

However, you will search long and hard to find a photo that shows this unless it is very heavily processed. Even then it would be rare. I've never seen this. Actual photo images have at least a bit or two of noise and, since there are thousands of printed pixels in even a tiny area. The effect is blended and so not seen.

[Mark D Segal]

"But it will at some point even if it's barely noticeable overall your image will definitely have smoother gradient at 16 bit then at 8 bit, it's a fact".

Keeping the above quote in mind it seems to me that this thread has become somewhat convoluted with overlapping references to both 16bit processing and 16bit printing(if there is indeed such a thing).  I will freely admit that the possibility that I have misread some of the thread is quite likely, but I do believe that the above quote seems to prove my theory of overlapping subjects.  I just checked again to verify the intention of the OP and I was correct.  It was not aimed at the value of processing a file in 16bit, it was instead aimed at printing in 16bit -- again, if that is at all possible, which would seem to be in question here.  In this case I believe it would probably have been a good idea to address this difference early in the thread, so that we wouldn't be talking apples and oranges as has been the case in some replies.  YES INDEED, we do ALL realize and appreciate the advantage(s) of processing a file in 16bit.  However, that was never part of the initial question as I read it.  It was all about printing in 16bit and whether or not it actually makes any difference in the final outcome.  Unfortunately the lines/curves have become crossed and the final outcome is in doubt as I see it. 

My rant for the day.  Likely nothing of any value, which I imagine will be pointed out soon, and welcomed 

Gary

It's always good to be brought back to the original question, as discussions can and do meander and I may have been one to contribute to the meandering for all I know!

So, the O/P was asking whether there is a way to test for sure that a 16-bit data stream is being sent to and used in the printer. For a fulsome discussion of the matter, (perhaps more than the O/P originally intended!), there are perhaps three questions in one here: (1) Is it happening (16-bit data going right through the processing to the print head)? (2) How can I find out for sure? and (3) Does it matter? The conversation here has pointed to ways of trying to answer all three, which I think makes it a more interesting discussion. I don't know where that leaves us, or whether the O/P is satisfied with the feedback.

Personally, on this one, I would be prepared to accept the technical representation, for example from Epson and Adobe, that 16-bit means 16-bit - that the data being processed through the editing software and handed over to the printer driver is 16 bit data, and the printer driver then uses this data, inter alia, for determining the ink recipe being laid down on paper. I don't believe there is such a thing as 16 bit printing, but there is 16-bit data being processed. 

[digitaldog]

Thanks for the file, it seems super at first glance, I'm curious about one little thing though, at the top of the sheet it says ProPhoto  RGB 16 bit data, so why the file profile is Adobe RGB?

The document absolutely isn't in Adobe RGB (1998). I downloaded it again, it's in ProPhoto RGB. Sounds like your Photoshop color settings are set to automatically Convert and your RGB working space is set to Adobe RGB (1998) or you're converting this elsewhere but no, it's in ProPhoto RGB.

Here is an answer that everyone can verify probably even with a scanner, using the CIE76 Delta E metric and even considering that this metric is not uniform across the spectrum, ie we can see some color difference better then others and that I tested only a few RGB triplets by changing just on color by one 8 bit level say (100, 100,100) compared to (100,101,100), I converted each of those to (XYZ) and then to L*A*B* then applied both CIE76 Delta E and CIEDE2000 and the result are under the just discernible threshold according to my reference, in other words we can't see it

You're getting yourself into a bit of a rabbit hole here. First, dE 76 isn't an ideal formula for reporting small differences in color distance. The scanner isn't the appropriate tool, a Spectrophotometer is. And you can take a very high quality Spectrophotometer like my iSis XL and measure the same print containing solid patches and you'll NEVER see anything close to dE 0.00 due to noise inherent in the device. A fraction of one dE sure, on a good unit. And a dE of 1 or less may or may not be visually perceptual; as a 'rule', we state that less than one isn't a visible difference but it depends again on where in color space you examine the distance. It's why an average dE report, with a good amount of sampling (hundreds or perhaps thousands of measurements) along with the max dE of one patch is useful here. If you measure 500 colors and 499 are all under a dE of 1, but one patch is dE 1.6, that's quite telling. Lastly, consider few targets for creating actual ICC profiles for print are high bit but rather 8-bit per color. Why? Because of the facts outlined already: few printers will use the extra precision of numeric data (device values), and it's just not necessary. If the people making software to create profiles don't feel the need for the extra precision, why go there?
Next, I can't fathom how you'd need to measure solid color patches this way after printing with 16-bit vs. 8-bit. Just output a print and look at it.

Think of this, suppose that on this or that print, you have say in 16 bit a value just barely above the 8 bit level of say 100 and the value of next pixel to it is halfway between 101 and 102.

You're mixing up device values with measured colors and the distance between adjacent colors based on Lab and dE (and the various possible formula). See:
http://digitaldog.net/files/ColorNumbersColorGamut.pdf
You can see how two sRGB values can have differing device values and be the same color with tiny dE differences. Two differing values in 8-bit per color might and can produce a dE higher than 1. Depends on the color space, depends on the two sets of triplets and which differ by one value. But this is really again, a rabbit hole that isn't necessary in confirming if or if not, 16-bit vs. 8-bit per color makes a difference visually or even if the driver did or didn't convert the data from high bit to 8-bits per color somewhere in the print path.
Can you output 16-bits of data to a printer? Well yes you can. Can you see a difference doing so? I don't believe you can. Is this really even 16-bits of data or instead 10, 12- or 14-bits of data? If you're using Photoshop, you're not even truly working in 16-bit!
The high-bit representation in Photoshop has always been "15  + 1" bits (32767 (which is the total number of values that can be represented by 15 bits of precision)   1).  This requires 16 bits of data to represent is called "16 bit".  It is not an arbitrary decision on how to display this data, it is displaying an exact representation of the exact data Photoshop is using, just as 0-255 is displayed for 8 bit files.
High bit (what some are calling 16-bit but probably isn't that specific encoding) is about editing overhead. All you need is the best 8-bits per color to be sent to an output device. Often, very often, that's all you can send to the hardware anyway. But you have a document you can test to visually see if there's a difference you see printing both ways as I outlined. You don't have to measure anything especially if you don't have the correct measuring device to do so; a high 'accuracy' auto Spectrophotometer.

[elliot_n]

I just printed Andrew's test file on my Epson 3880, with the 16bit checkbox checked, and then unchecked. I couldn't see any difference in the resulting prints. I scanned the prints, layered them in photoshop, and toggled between them. I still couldn't see a difference.

[Mark D Segal]

I just printed Andrew's test file on my Epson 3880, with the 16bit checkbox checked, and then unchecked. I couldn't see any difference in the resulting prints. I scanned the prints, layered them in photoshop, and toggled between them. I still couldn't see a difference.

How about if you were to examine them considerably magnified? Any difference then?

[elliot_n]

How about if you were to examine them considerably magnified? Any difference then?

The prints were scanned at 600dpi on an old and dusty Epson flatbed scanner (Perfection V30). Viewed at 200% in Photoshop, and toggling between the 8 bit and 16 bit print, there are very slight differences when looking at the big square with colour gradients. But nothing significant - it's not that the 8bit has lots of banding, and the 16 bit print has none... rather the placement of the banding seems to change slightly between the prints. The real-life images (fish, boat, textiles) look identical.

[digitaldog]

Make two subsequent scans of THE SAME print. Dollars to doughnuts you'll see differences due to minor registration differences. This is noise. Different in production but not in the results of scanning the same set of targets two times in a row on an auto Spectrophotometer. Which is why if you examine a dE report of two such scans on an auto Spectrophotometer, you'll again NEVER get a 0.00 dE report. 0.09, fine. 0.00, never.

[elliot_n]

Yeah, I figured it was noise.

[deanwork]

We all know that drum scanning in 16 bit or dslr shooting in raw, then processing outputting these files in 16 bit  recorded more tonal data, but no one has done a definitive test that I know of that shows an obvious ( perceivable) difference in print output as a result of checking any 16 bit driver box. I’ve done comparisons with Epson 9890, Canon IpF 8300, and HP z3200, with Oem drivers and third party monochrome rips and I can’t see any improvements from a visual standpoint. ( have not tried with Studio Print or Image Print comparisons though ).

So my question to the software specialists is - why do all the top three printer manufacturers even offer it as an option at all? We’ve been asking this question for about 5 years now and I’ve never learned a logical answer.

John

Yeah, I figured it was noise.

[faberryman]

If you can edit and print in 16-bit, there is no reason not to. Most people can with the software and hardware they have, so its free. Do so, and avoid all the hand-wringing and angst.

[Doug Gray]

So my question to the software specialists is - why do all the top three printer manufacturers even offer it as an option at all? We’ve been asking this question for about 5 years now and I’ve never learned a logical answer.

John

Marketing! Because 99% of people that buy or specify printers just assume 16 bits is better than 8. It's very logical from the point of view of keeping your production line humming.

[digitaldog]

We all know that drum scanning in 16 bit or dslr shooting in raw, then processing outputting these files in 16 bit  recorded more tonal data, but no one has done a definitive test that I know of that shows an obvious ( perceivable) difference in print output as a result of checking any 16 bit driver box. I’ve done comparisons with Epson 9890, Canon IpF 8300, and HP z3200, with Oem drivers and third party monochrome rips and I can’t see any improvements from a visual standpoint. ( have not tried with Studio Print or Image Print comparisons though ).

They record finer encoding of numbers. That doesn't necessarily mean anything else visible or otherwise. Improvements in output from what you call RIPs (which may not be but are 3rd party drivers) are not necessarily due to anything having to do with encoding and it's darn difficult if not impossible to pinpoint why one driver produces visually superior prints than another. Just look at say the linearity of output from say an Epson native driver and that from ImagePrint. Can be significant and have absolutely nothing to do per se with bit depth.
Again (and again), high bit data is about data overhead for editing our data. There's always data loss from the rounding errors when we edit numbers. Which is all computers understand. When you aggressively edit an 8-bit per color image in Photoshop or similar, the rounding errors can (repeat can but may not) reduce the data to far less than 8-bits of good data and the result is banding in smooth gradients like a sky, chrome bumper etc. Do so in high bit, it's moot; more than enough data to produce 8-bits of good data for print.

[Garnick]

The prints were scanned at 600dpi on an old and dusty Epson flatbed scanner (Perfection V30). Viewed at 200% in Photoshop, and toggling between the 8 bit and 16 bit print, there are very slight differences when looking at the big square with colour gradients. But nothing significant - it's not that the 8bit has lots of banding, and the 16 bit print has none... rather the placement of the banding seems to change slightly between the prints. The real-life images (fish, boat, textiles) look identical.

"Viewed at 200% in Photoshop, and toggling between the 8 bit and 16 bit print, there are very slight differences when looking at the big square with colour gradients. But nothing significant"

Of course I cannot speak for Mark, and he can certainly correct me if I have misinterpreted the above quote.  However, I believe he was referring to examining the actual prints magnified instead of the image files enlarged in Photoshop.  As with most cases, when one is trying to determine a difference in a particular method of image file processing and or printing, the proof is in the print.  Of course that also depends on whether or not a print will be the end product.  Yes, the numbers are useful on some level, but in the end the print tells the tail, does it not?  I have yet to sell the image on my display to one of my customers, but they are very happy and satisfied with the prints I produce from their files.

Just wondering .... 

Gary     

 

[elliot_n]

I was looking at 'the actual prints magnified' — I was just using a scanner instead of a loupe to do the magnification.

(I've also looked at the prints with my eyes (with and without a loupe), and again, I can see no difference.)

[faberryman]

(I've also looked at the prints with my eyes (with and without a loupe), and again, I can see no difference.)

I'm curious what printer you are using. Is there an advantage to printing 8-bit?

[elliot_n]

I'm using an Epson 3880. I normally print in 16-bit, and I will probably continue to do so (even though my quick test has revealed that there's no advantage to it).

Depending on one's workflow, printing 8-bit might save some hard drive space.

[deanwork]

I know all that about editing. My point is why do these printers even have that 16 bit output option if their color scientists know there is no point in offering it as an option?

They record finer encoding of numbers. That doesn't necessarily mean anything else visible or otherwise. Improvements in output from what you call RIPs (which may not be but are 3rd party drivers) are not necessarily due to anything having to do with encoding and it's darn difficult if not impossible to pinpoint why one driver produces visually superior prints than another. Just look at say the linearity of output from say an Epson native driver and that from ImagePrint. Can be significant and have absolutely nothing to do per se with bit depth.
Again (and again), high bit data is about data overhead for editing our data. There's always data loss from the rounding errors when we edit numbers. Which is all computers understand. When you aggressively edit an 8-bit per color image in Photoshop or similar, the rounding errors can (repeat can but may not) reduce the data to far less than 8-bits of good data and the result is banding in smooth gradients like a sky, chrome bumper etc. Do so in high bit, it's moot; more than enough data to produce 8-bits of good data for print.

[faberryman]

I'm using an Epson 3880. I normally print in 16-bit, and I will probably continue to do so (even though my quick test has revealed that there's no advantage to it). Depending on one's workflow, printing 8-bit might save some hard drive space.

Not sure how unchecking the 16-bit box when you print saves hard drive space. The file is simply going to a cache and clears when the print data is sent.

[digitaldog]

I know all that about editing. My point is why do these printers even have that 16 bit output option if their color scientists know there is no point in offering it as an option?

Doug explains it in post #32 perfectly.
In the future, depending on the improvements in printer technology, it's possible we may see a difference.