Up-Rezing or Down-Rezing an image

[Erland]

Doesn't the 2400 have 5760 x 1440DPI, and the 3880 2.880 x 1.440DPI as max resolution? And that is why the max of 720 vs 360 in the options?

[dwswager]

Those are possible settings for faster output, because less resampling will have to be done by Qimage. That can be useful for poorly written printer drivers that choke on the number of mega/giga pixels it gets sent after interpolation, and huge billboard output doesn't need such high resolution at all, so one might as well speed up the preprocessing.

The (for this discussion) relevant number is the feedback as reported at the top right-hand side of the Qimage window (see attachment for one of the printers I have currently attached). The values will vary with the settings of the printer driver, e.g. output medium.

Cheers,
Bart

Oh, I see now.  Went into 3880 printer setup through Qimage and selected EEF and Highest resolution and finest detail.  Got different max and low settings.  Actually interesting.  Setting the printer to the highest quality of 2880x1440 w/ Finest Detail check and EEF as the media, means the printer will use the a 2880x1440 dither pattern option and yet Qimage will resample to one of 4 different resolutions 180, 240, 360 and 720 while the printer uses it's finest capabilities.  Hmm.

Now I really want to see what gets returned to an DC_ENUMRESOLUTIONS because I can't believe the printer would return 90 as an option.  

[dwswager]

Doesn't the 2400 have 5760 x 1440DPI, and the 3880 2.880 x 1.440DPI as max resolution? And that is why the max of 720 vs 360 in the options?

Yes, the R2400 has those available resolution.  But again, those are not what gets printed, but what is available to get printed.  The dither pattern can be calculated using a 5770x1440 matrix.

As Bart pointed out, Qimage does not set the printer resolution.  You have to go into the printer driver setup dialog to do that, just like in Photoshop.  What it appears you are setting in Qimage is the resolution of the data sent to the printer driver.

[Bart_van_der_Wolf]

As Bart pointed out, Qimage does not set the printer resolution.  You have to go into the printer driver setup dialog to do that, just like in Photoshop.  What it appears you are setting in Qimage is the resolution of the data sent to the printer driver.

Correct, the PPI is set as a result of a combination of printer driver choices, and the DPI (dots!) settings are for the dither pattern. Qimage just reads the PPIs that are expected, and does a higher quality resampling than the printer driver offers, output sharpen that at the native printer resolution, before sending that to the printer driver for dithering.

Cheers,
Bart

[Bart_van_der_Wolf]

Doesn't the 2400 have 5760 x 1440DPI, and the 3880 2.880 x 1.440DPI as max resolution? And that is why the max of 720 vs 360 in the options?

In a way, yes. The dithering pattern is used to produce intermediate ink colors and make the pixels and subsequent printhead passes weave into eachother without abrupt pixel changes. The DPI (dots for dithering) settings are somewhat related to the PPI (pixel resolution) settings. It doesn't make much sense to dither a coarse resolution like 360 PPI with 5760x1440 dots unless one has a limited number of ink colors, it's a bit overkill for the production of intermediate ink colors if the pixel resolution is already high.

Cheers,
Bart

[Ernst Dinkla]

I do not doubt that the Epson printer responds to the Enumerate Resolutions function.  I no longer have development environments, nor the driver development kit installed on my machines so I can't verify for myself or report here what response the printer gives.  What I do know is that the response is to provide the application with the available resolutions as choices to the user. (I might have to reload some of this stuff to actually monitor/capture the data just to see what is going on.  If I do, I will post findings).

I loaded Qimage to see how it uses this data and what it gets.  Attached are images with the Epson 3880 and 2400.  For the 3880 Qimaged offered resolution choices of 90, 180, 240 and 360.  For the 2400 it offered resolutions of 180, 240, 360 and 720.  I assume based on what I see in the print dialog that Qimage itself will re-sample to this resolution, though re sampling is not necessary.  The surprises here to me are on the 3880 with inclusion of 90 and the max of 360.

If you keep Qimage's extrapolation set at MAX it will pick the highest input resolution requested by the driver. Any setting below MAX will send less data to the driver but the general assumption is that the driver/OS? does the extra resampling to the requested input resolution then. Whether a lower setting in Qimage speeds up the pre-print processing is dubious, the anti-aliasing algorithm in Qimage may take more time than the upsampling algorithm does, in my experience. A recall print run from the log file will set both Qimage's extrapolation settings (MAX and algorithm type) and the driver print quality settings like they were when the original job was run. So in that case Qimage takes more control of the driver.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots

[dwswager]

In a way, yes. The dithering pattern is used to produce intermediate ink colors and make the pixels and subsequent printhead passes weave into eachother without abrupt pixel changes. The DPI (dots for dithering) settings are somewhat related to the PPI (pixel resolution) settings. It doesn't make much sense to dither a coarse resolution like 360 PPI with 5760x1440 dots unless one has a limited number of ink colors, it's a bit overkill for the production of intermediate ink colors if the pixel resolution is already high.

Cheers,
Bart

I would argue with your characterization of 360ppi as coarse.  In continuous tone terms that is actually very good.  In dithered terms, it is still very good and almost indistinguishable from 720ppi in real world application.  The vast majority of people would be unlikely to identify which was which between prints made from the identical input file: one at 360ppi and the other up sampled to 720ppi in a blind test.

[Added]
As an input resolution in pixels per inch, 360 is very good since it is continuous tone.  According to Kodak, for example a 35mm film frame had about 3600 x 2400 pixels or real resolution available or at 360ppi 10"x6.67".  I think we are getting spoiled!  Now if you were talking about a 360x360 per inch dithering pattern using only 8 colors then, yeah 360 would be fairly coarse.  Beyond about 300ppi we are getting into an area similar to $100 worth of monster cable versus $5 worth of 18 gauge zip cord: While some people might actually hear a difference, they can't identify it. 

With respect to printing at 5760 for dithering, it is important to always keep in mind that the printer will not lay down 5760 dots, but will have available to it twice as many potential dot locations in that linear direction than printing at 2880.  Which is why Epson has never been a big horn blower over the increased resolutions of some of these printers.  When pressed, they will flat out tell you that you won't see a difference, except under specific unique circumstance that they won't divulge, between 2880 and 5760. The other complicating factor is droplet spread and ink load properties of the media which is why selection the media type influences the resolutions available.  This is why they do tout EEF.  It takes a rather high ink load for a gloss paper in combination with the smaller droplet spread that characterizes gloss papers.