Re: Photo Print Quality issue Canon G2000 series

On Wed, Dec 30, 2020 at 12:20 AM Jonathan Ing <[email protected]>
wrote:

> Hi, I am using the gutenprint v 5.3.3-4 on Ubuntu 20.04-1 and I notice
> that when printing photos (I am using 4x6 glossy, photo mode) and pictures
> have a low bitrate look to them... almost pixelated. I have set DPI to max
> 600x600 and nothing seems to help. Not sure if this is a potential bug?
>

Hello,
I am sure photo printing will not be good without some serious tuning of
densities in CUPS, since the Canon driver does not include any calibration
of colours.
However, maybe you can get better results if I explain the process, what
you are saying about resolution is not really how it works.

Firstly, the Canon printheads only have resolutions of 300dpi or 600dpi
(some have a single mode that is at 1200dpi).
So "setting resolution to X dpi" is not what determines the quality.
The firmware uses the physical printhead resolution, multi-pass printing
and complex algorithms making use of the available physical inks, to print
at some "effective resolution".
The above process, and/or the possible quality, are different for each
media type.

Thus, when you select a resolution, you are not seeing a simple "X dpi"
name for the resolution,
what you see is a "resolution mode" name, such as "High quality (600 DPI)",
for example.
Each media type has several possible resolution modes associated with it,
and hints are given in the drop-down, so that users do not attempt to use,
say, plain media modes, with photo media, or vice versa.
If a resolution mode is chosen that the firmware does not know about for a
particular media type, the printer will generally not print.

So to prevent non-printing, if a non-compatible mode is selected in the
Canon driver, then there is a forced selection to a similar quality mode
accepted by the media.
As a result, depending on the other options apart from media type (e.g.,
double-sided printing), you might not be printing with the mode you think
you selected.
The only way to be sure is to check the debug logs (setting them up in the
CUPS interface).

The G1000, G2000, G3000 share a common driver, with the following
resolution modes available:

A. For plain media

600x600 DPI HIGH
600x600 DPI
300x300 DPI

B. For plus Glossy II only

600x600 DPI PHOTO HIGHEST plus Glossy II

C. For other photo media

600x600 DPI PHOTO HIGH
600x600 DPI PHOTO

D. For envelope and hagaki (postcard) media

600x600 DPI HIGH (Env/Hagaki)
600x600 DPI (Env/Hagaki)

If you are trying one of the photo media resolution modes, and it is of
poor quality, the tuning of the density of individual inks is probably way
off.
Tuning is a lot of experimental effort, but you can try with the CUPS
density controls for the different channels to see if you can improve
matters.

Best regards,
Gernot Hassenpflug

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