I have a side question about print resolution. I hope it is not off-topic, as it relates to how the "normal" human eye can appreciate high resolution in print.
Kodak is making an industrial bet on their digital high-resolution printing technology. Until today, high-quality print as far as I know is made at 300 pixel per inch. It seems that very rarely recourse is made to 400 ppi printing. The new Kodak technology is supposed to deliver prints at 600 ppi (at high speed). Photographic paper resolution (darkroom) is > 60 lp/mm.
So my doubts are:
Which is the correlation between line pairs per millimetre and dot per inch? What would be the equivalent, in lp/mm, of a 600 ppi print?
Is the higher quality of this higher resolution discernible by the average person?
Are printed publications going to require, or sistematically adopt, in the future, a higher resolution?
The answer to these questions might have side effects also on photographic prints (darkroom work). People might, with years, form different expectations about sharpness. A fine-art print that looks sharp on a gallery now, might look less sharp in twenty years time when people will have seen thousands of images printed in books at 600 ppi (if really Kodak succeeds in bringing forward this "revolutionary" technology).
Maybe 600 ppi is in any case less than 60 lp/mm but the "visual resolution gap" between a book and a fine-art print will be reduced.
Fabrizio