Hello,
I must confess that I was still a bit skeptical about the advantages to up-sample to 300 or 600ppi (I use a HP Z3200) before printing, but reading Jeff and Ernst insisting (once again) that LR 3.x and Qimage algorithms are optimised to work that way I decided to give it a try. I own both softwares but usually print from Photoshop (or used to).
Today two clients cancelled their appointments giving me about to 3 hours free to play, so I carefully selected an image that was sharp, had various different textures and some low and high contrast areas. The image would be about 242ppi at 24" width. First I processed the image as I usually do and printed it 6 times on Cansosn Photo Satin Premium RC 270g paper on the following order:
1) Printed from PS without up-sampling at 242ppi
2) Printed from LR3.5 without up-sampling at 242ppi with "standard glossy" print sharpening
3) Printed from LR3.5 up-sampling to 300ppi with "standard glossy" print sharpening
4) Printed from LR3.5 up-sampling to 600ppi with "standard glossy" print sharpening, printer set to "maximum quality" (I know I should do that only if the image was originally above 300ppi, but I did just for fun)
5) Printed from Qimage up-sampling to 300ppi with "standard" print sharpening, "fusion" interpolation
6) Printed from Qimage up-sampling to 600ppi with "standard" print sharpening, "fusion" interpolation, printer set to "maximum quality" (again just for fun)
Then I numbered the prints and spent about an hour looking at them side by side on the light booth. I also showed them to my wife (and business parter) and some other photographers. Everyone agreed that (1), (2) and (4) were the worse in therms of sharpness and detail, proving that Jeff Schewe is right (as usual). But, curiously, there was no consensus about images (3), (5) and (6) and honestly I would approve any of those if presented separately. Image (6) was the anomaly, would not dare to say it is sharper and has more than (3) and (5), but it for sure is no worse.
I will try to test some other image tomorrow, this time an image that is above 300ppi.
Many thanks Jeff and Ernst, as I am now convinced!
Best regards.