Okay. Yes, that was already very useful.


Understood. Thanks for the further improvement. It's the attention to details that makes a difference, even if only visible in special cases.

Cheers,
Bart

Hi Mike,

Could you elaborate a bit? Has the dithering changed, or something else that would warrant reprinting some earlier stuff. I've not seen a specific mention in a video about it yet, hence the question here.

I know I could try but, to avoid wasting paper and ink, I'd like to target those tests at something that might be specifically affected. So what is it we are looking for, besides smooth gradients in general (color, gamma related things, large gradient features or small)?

I also wonder about the 'monitor gradients', in what way they are affected, and how that correlates to the printed output which is at a different scale.

Thanks for the continuing efforts to improve our image output, and print workflow.

Cheers,
Bart

Thanks Mike,

That makes a lot of sense. As I said, it was not clear what driver settings were used, so it might have been user error.

Do you think that the high(est) quality setting like 2 or 1 in Canon drivers makes any difference on uniform colors (like in the purge patterns), or is it basically only used for rendering of the finest possible details and color dither mixing?

Cheers,
Bart

Hi,

I've searched the forum but did not find an answer, so here it goes.

On another forum https://www.dpreview.com/forums/post/58860582) a remark was made that there is not a 100% certainty that all nozzles of a color that are selected get purged. Unfortunately, the poster there did not mention which paper settings were used in the printer driver.

On another forum someone made a remark about the possibility (without further details) of one particular ink being missed, so I'd like to have this cleared up if possible (to prevent the rumor mill from spreading incomplete/wrong information). Maybe there is some more info available that can help in choosing the best media settings in the printer driver, to make sure that the intended colors get proper attention.

For the above mentioned issue of Vivid Magenta not being addressed by choosing Magenta, maybe there is another media choice that would use it?

Also, I've noticed in my media settings for particular media of my Canon printers, only a choice of "Platinum" paper allows me to select the highest printing quality (and thus highest resolution). I'm not sure if that quality setting (2 or 1) makes any difference for the unclogging of all nozzles (by using a different dither pattern), or if that only affects the precision of mechanical positioning.

Sofar I've chosen that Platinum media choice at the highest quality setting of 1, in the assumption that it will exercise all nozzles.

Maybe there are other combinations that will miss some of the nozzles, and should be avoided?

Cheers,
Bart

Hi Alan,

AFAIK,  "Image Read Error" on the TIFF thumbnails may (in this case of multiple large files) be caused by lack of continuous RAM memory available for allocation by the Operating system. Try reducing the number of Multi-threading cores that are used for the creation of thumbnails (Edit|Preferences|Multithreading). With many large files that are simultaneously loaded in multiple processes, the available Operating System (OS) memory could be insufficient.

Holding the shift key, while clicking "Help|Analyze Current Settings" will display the amount of available OS memory.

Cheers,
Bart

Deleted, Might be an non-QU issue.

Cheers,
Bart

Thanks Mike,

This really makes a difference, for the better rendering of smooth gradients like in the sky, and in lower contrast shadows, or generally low contrast surfaces. This will allow to use higher DFS amount settings without those areas getting 'gritty' or posterized.

Cheers,
Bart

Okay, so I'm not overlooking something, and the zoom levels mentioned were referring to the fixed fractions/multiples one can select in the preview window.

That our displays will not be perfectly accurate for predicting how actually printed output will look, is understood, and I agree. Although, having said that, there is some capability to judge the expected appearance better than we can do now.


I understand that that is the goal, but it would first require to produce actual output to arrive at the optimum Smart sharpening setting for a given subject matter and specific output medium.

Pressing Ctrl-X will give a 100% preview of the original pixels in the image, but that is a display that is much larger than the final printed size will be, and obviously without the effects of interpolation and output sharpening. What would already give a better impression is if one were able to e.g. zoom out to an arbitrary zoom level that produces the same size on display as the final print will be. Such an arbitrary zoom percentage would be almost exactly the same as the 'display PPI / Printer PPI' ratio I mentioned earlier.

I understand that at this stage, there will neither be any output resampling nor Smart sharpening, because we are looking at the source image  pixels. However, if we were to print to file, and use the image Examiner on that, then there would be interpolation and Smart sharpening, and zooming out to e.g. 96/600 % (or 128/600 % in my case, or 128/720 if printing to an Epson) would give a pretty decent (not perfect but decent) impression of how the output will look at the viewing distance we are watching from. So even without having spilled a single drop of ink, we are able to get an impression, and perhaps crank up the Smart Sharpening a bit, because the sharpened edges and features will have the accurate size (=angular visual resolution), despite the relatively low resolution display.

Some subjects can benefit from more sharpening than others, and it would be wasteful having to first print it to find out if we could have know before by using a proper zoom factor. We would also need to take notes if we have significantly different types of subject in the images we print.

Again, I know it won't be perfect, nothing beats an actual print to judge the effects of the full processing pipeline (some papers are sharper than others due to ink diffusion), but close enough is already a lot better than nothing.

I think that having more choices than 50%, 25% or 12%, would make a lot of people happy. On my 128 PPI display, I would need to watch at either 128/600= 21.3% for Canon/HP output, or 128/720= 17.8% for Epson output, for a true output size display. It's something I can do in Photoshop CS6 at the click of a button, after setting my display PPI in the preferences, and the output PPI comes from the PPI tag of the output file. Of course printing from Photoshop is a nightmare, so I'd rather not have to use Photoshop for judging.

Cheers,
Bart

Gentle bump ...

Anybody who knows where this zoom feature can be activated is welcome. The wish for a really useful preview of the sharpened output before actually printing is also coming from others http://www.luminous-landscape.com/forum/index.php?topic=92128.msg750850#msg750850, so it would be too bad if it is already there ...

Cheers,
Bart

Hi Mike,

Sorry for going back so many versions, but how does this work? I cannot find (probably overlooked) where to set the zoom level to any zoom level.

I was going to suggest a feature to do this in the Image Examiner window, e.g. set zoom on a print file output to exactly (display PPI / Printer PPI) zoom percentage to achieve the same preview size as the output would be. But apparently it is already somewhere.

Cheers,
Bart

Hi Mike,

I agree, the likelihood of spotting it is slim, and if only a single bit in an RGB triplet is affected it's even less likely. I have however seen in the output dither that R and G and B were all affected in the same way. Maybe I need to check some more samples of both input (16 -> 8 bit) and output (profile) dither to see if that was an accident or not.


Okay, I thought there was something in LCMS 2 because in my perusals on the LCMS site, I couldn't find anything about the dithering, yet in the source-code there was a Boolean Dither Flag or something like that. Maybe it's a remnant of the previous version.


Yes, chance has it that it's gone due to interpolation. However, if the resampling factor effectively is 1.0 (image 600 PPI, output also 600 PPI) or something very close, the Smart output sharpening might enhance the earlier image dither, and add another layer of dither after that. To avoid the reinforcement of the dithers, maybe a fourth option would be safe to cover all grounds?

Something like:

• None
• 16 bit images only
• Profile conversions only
• Full (16 bit images and profiles)

Agree, it's just something one should be aware of when creating a filter that sharpens.

Thanks again for providing some more insight into the inner workings.

Cheers,
Bart

Hi Mike,

On the release notes of v2.18 it is mentioned:
v2014.218 offers improved dithering for 16 bit images and profiles plus some bug fixes.

This adds the following Dithering options to the Color management panel:

• None
• 16 bit images only
• Full (16 bit images and profiles)

Could you elaborate about the 16-bit images option. Does that dither 16-bit/channel images on input conversion to 8-b/ch? If so, doesn't that carry the risk of magnifying/enlarging whatever dither there might be visible when adding a filter sharpening in the image editor, and enlarging that with output upsampling?

I've also seen that the output dither has a checkerboard pattern. Is that part of the LCMS colorspace dither option? Is a checkerboard pattern safer than a stochastic pattern to avoid clashes with the printer dither pattern, or just faster? It may not matter much at the native printer driver resolution (600/720 PPI), although we have the option to use a lower resolution and the printer driver may be set-up to a maximum of 300/360 PPI, but I'd like to understand the pros and cons.

Thanks for the additions.

Cheers,
Bart

Hi Luc,

Indeed, I think it would be a mistake to dither this soon in the processing pipeline (upon opening the file), even before resampling to output size and output sampling.

It may also be useful to send Mike a copy of your Output profile, although you say that with that same output profile PS/LR do not exhibit as much posterization/banding. It might also be interesting to try Raw converting the image to pRGB or BetaRGB instead of ProPhoto RGB (PPRGB), and see if that makes a lot of difference in this particular case.

Cheers,
Bart

Hi Mike,

Great to hear you've considered it, but decided not to use it due to potentially worse results. Maybe the dithering in LCMS 2 has improved, let's hope. We're in principle talking about a maximum of +/- 1 in 256 randomness, which even differs per channel, which should be imperceptible especially on printed output. But maybe the implementation in LCMS 1 was something else, more pattern based, I don't know.

The quest for perfection continues.

Cheers,
Bart

One more question: Does Qimage use the LCMS Dither option? Dithering adds an imperceptible amount of randomness to the individual channels, and is a customary operation when trying to avoid posterization/banding in smooth gradients in 8-bit/channel space.

Cheers,
Bart