On Wed, 18 Feb 2004 08:59:38 +0000, Steven wrote:
=>Hi
=>Just looking for confirmation I haven't got this all wrong,
=>
=>My camera kicks out 1536x2048 pixels and I want to get the best print onto A4 and I suspect `scale to fit` doesn't change the print resolution??
I presume that the 1536x2048 is the _screen_ resolution, as
displayed on your monitor (If not, see below). This has
nothing whatever to do with printer resolution. That is,
there is no easy or obvious way to translate from one to
the other. A screen pixel actually consists of a triad of
dots (cyan, magenta, and yellow), and a printer dot is just
a dot of ink.
A printer resolution of 300 dpi (roughly 12 dots/mm) means
just that. However, a printer _pixel_ consists of four
dots, cyan, magenta, yellow, and black (Some printers use
6, 7, or 8 dots per pixel.) These pixels are more less in a
line, and overlap more or less, depending on the printer.
Note that a printer's resolution is given as (for example)
1200 x 600. That means 1200 _dots_ per inch horizontally
and 600 dpi vertically. It does _not_ mean 1200 x 600
pixels. It actually works out to about 300 pixels per inch
horizontally, minimum. If the printer places the dots in a
triangular or square pattern, then there will be more
pixels per inch. It also means that the lines are slightly
overlapped, which gives you the illusion of continuous
tone.
As for camera pixels: I'd like to know! Are these pixels
"real" pixels, ie a triad of C-M-Y dots? If so, then camera
resolution is the same as screen resolution. Or are they
the dots themselves? If so, then screen resolution will be
much less. But either way, the relationship to printer
resolution is not a simple one.
Then there's the software. When resizing the picture for
printing, the software processes the colour information
along the lines of: "To find the colour of an output pixel,
take a certain number of input pixels, and calculate."
It's that "calculate" that's the spoiler. There are many
different methods, and programmers have different opinions
on what to do. The printer driver then has to take the
output from the image processing software and translate
that into colour information it can handle - which means it
does the same sort of calculation as the ImProc software
did! In my HP660C printer driver, I can even select the
algorithm used to do this.
So you see, translating what the camera sees into what the
printer prints includes so many steps that it's impossible
to say whether your calculations have any semblance to
reality. In general, it's best to use ImProc software to
resize the image, not the printer driver -- but a
combination may work better in your case. IOW, no matter
what, you will have to experiment. NB that ink + paper
combinations also have an effect on the quality of the
print, including apparent sharpness. And, because colour
printing is a matter of illusions, things like colour
balance, contrast, and sharpness also play a role. That's
why ImProc software exists.
