John Francis wrote:
Yep. I must admit we usually talk about DPI (not PPI) where I work... (See http://www.procaptura.com.)On Aug 28, 2004, at 12:08 PM, Doug Franklin wrote:
On Fri, 27 Aug 2004 20:09:45 +0200, Toralf Lund wrote:
[...] to get real picture quality, you ought to have enoughMost paper can't hold more than 200-300 dpi.
information to print at 1200dpi [...]
Just to be pedantic...
DPI (dots per inch) applies mainly to halftone processes such as inkjet printers. It refers to the minimum offset distance between two dots. Each of the two dots can be any component colour (usually C, M, Y, K). So the higher the dpi figure, the closer the dots can be printed together, and the "smoother" the image will look from close up.
PPI (pixels per inch) describes the amount of actual information present in the image.
Continuous-tone processes are an exception as the component colours are placed on top of each other, so in this case dpi and ppi can be used interchangeably as the numbers are equal anyway. Scanners and digital minilabs work this way. I think dye-sub printers are like this, too.
Mightn't that reduce the "pixelation" effect, i.e. produce an effect somewhat similar to pixel interpolation?Marketing people love to create confusion between these concepts... which is why people tend to refer to dpi all the time as this gives the bigger numbers.
As has already been pointed out, printing with wet inks (the technology basis for home inkjet printers) is limited by the paper; ink spreads and merges before it dries. Even the 200-300 dpi figure above is generous when it comes to positioning acuracy (wet paper stretches significantly).
A high clay content glossy photo paper is as resistant to ink spread
as most things, although plastic film will do a little better. But
you also run into the problem of adjacent droplets merging together
before they have had time to dry, which constrains the final figure.
The bottom line is that even the 600ppi (base figure for the HP lineBut how about real photo paper, i.e. the variant(s) used by labs and/or traditional enlargers rather than the inkjet version? (Or was that what you were referring to above?)
of 1200x4800 dpi photo printers) or the comparable 720ppi from Epson
is overkill for printing multi-coloured images on everyday media.
Also, would laser printers give better results because the process (as I understand it) is a lot "drier"?
Not to mention that 600ppi for a 13x19 image takes 1/4 GB of data.
My point exactly.
