Re: Photo Print Quality issue Canon G2000 series

Hi Gernot,

Thanks for this wonderful explanation - I have no background in tuning
drivers before so this makes a LOT of sense! One question I have is then is
there any resource or guide for CUPS density controls? For example, if you
see x, y or z, increase or decrease this parameter?


Thanks!


On Wed, Dec 30, 2020 at 4:57 AM Protea Wines Japan <[email protected]>
wrote:

> 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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