I have downloaded the trial version of Qimage, but I am not going to have any time to test it out for a while, as I am going away next week. I just had a brief look at it, and so far I have to say I found the user interface a bit off-putting.
Doing tests like this certainly forces you to re-think a lot of assumptions, which is a very good thing. My first reply to Mike on this thread was basically correct on procedure, but backed up by the wrong science. Essentially, the reason that upsampling a file to 360 or 720 in LR produces a better print is probably absolutely nothing to do with some hypothetical matching of image resolution to printer resolution (as I implied), and everything to do with the fact that LR upsamples the image using some pretty neat anti-aliasing and smoothing routines. The results I have come up with now are strictly empirical (they work, but I’m not entirely sure why) and the hell with the theory.
Which leads me to another thought, and an incorrect assumption. I notice when running these tests that at 720 ppi size and output, even with an 8x loupe on the print I cannot see anything like the detail which is in the original file at 100% on screen. I still don’t see all this detail at 360 ppi (equivalent to a 20x15 ins print), and in fact it is only at 180 ppi (equivalent to a 40x30 ins print) that I can see everything on the print that is in the original file. Upsampled in LR to 720 ppi this prints as smooth as you like and is in fact the closest representation of the original image. Which means that, up to a certain point (which is probably about 180 ppi or so) the bigger you go with a digital image and an inkjet print, the better it gets. This is of course entirely contrary to darkroom printing, where the best possible quality is from a contact print from the negative, and anything larger than that progressively degrades the IQ.
Now I, in my innocence, had assumed that the best print quality would come from printing the file at exactly the same ppi as the highest output from the printer – so in my case, it would be a 720 ppi output file and 720 ppi from the printer, giving a print size of 10x7.5 ins. After all, one pixel in the file would print as one pixel on the page, so all of the image detail and information should be there. This would be my digital “contact print”. But no, it doesn’t work – in fact I don’t see anything like all
of the image data until I get up to 180 ppi or so. I’m really not sure why this is (dither pattern obscuring detail? Inability of printer to lay down a continuous tone in highlight areas? Droplet size too large?). It seems that to do what I would like to do (print very high-quality small prints) I would need a printer with a much greater nozzle density on the print-heads. We could speculate – the current Epsons have 180 nozzles per head, so perhaps I would need 720 packed into the same space with probably a sub 1 picoliter droplet size to do the job.
I don’t think that we will be seeing such a printer anytime soon – think of the clogging issues for a start