That's a strange viewpoint Pascal. I could have understood 'we don't upscale yet' or even 'upscaling is only available if your print driver can provide it' or even 'we just don't want to do this, you'll have to use an external program' but I can't understand the viewpoint that upscaling has no point except a bad quality print.
I've got some very high quality 16x10 prints on my wall at home from a 6MP sensor that with your logic could only ever print 6.25x4.16 at 480dpi. Admittedly I went to a lot of trouble to produce them and the final raster images were huge but it certainly can be done. I've also had very good results by upscaling images to the desired size at native printer resolution and supplying the, again extremely large, files to a commercial print service. Rgds, Rob. -----Original Message----- From: Pascal Obry [mailto:pas...@obry.net] Sent: 04 February 2015 18:08 To: darktable-devel@lists.sourceforge.net Subject: Re: [darktable-devel] print-module and black point compensation Hi Josep, > Mistery solved. My fault, print module works Ok with the Epson SX445W Good to hear! > The problem was that I was testing to print on it from Darktable using > a downloaded calibration image, the "Smugmug calibration print", that > has only 1400x1122 pixels. And the print module simply refuses to > print it larger than 100mmx80mm Ah indeed, darktable will never ever scale up an image. There is no point except getting a bad quality print. > With my own photos, at native camera's resolution, printing size is correct. Right, expected. The image must at least have the resolution of the printed size given the native printer DPI (300 or 360). > ---------------------------- > > The following is a little off-topic, but explains my initial intention: > I was testing the SX445W with this chart because I use it as an > inexpensive BW dedicated printer, I have replaced the original color > inks by MIS Ebony carbon pigment ink diluted to different levels, > following the methods described by Paul Roark (www.paulroark.com/BW-Info). > > I use this printer from GIMP applying to the BW images a custom curve > in the blue chanel, to force the use of the magenta and cyan > cartridges (both filled with medium gray ink) for midtones, and the > yellow cartridge ( filled with ligh gray ink) for the highligts. After > that I apply a lightness curve to correct the densities. > > I was hoping to do the same with darktable's print module ... but I > have not found the way to apply my custom curve for the blue channel. > Tone curves in darktable work in Lab space, and I don't know how to > create such a curve in Lab...(end of the off-topic part) And do you have a way to do that from darkroom? If so just create a style with the correction and apply this style from the print module. But I'm not sure we can adjust the blue channel from the curve. There was a discussion on the mailing-list about adding support for this in the tone curve. Not yet there, but there is hope :) Cheers, -- Pascal Obry / Magny Les Hameaux (78) The best way to travel is by means of imagination http://v2p.fr.eu.org http://www.obry.net gpg --keyserver keys.gnupg.net --recv-key F949BD3B ------------------------------------------------------------------------------ Dive into the World of Parallel Programming. 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