[filmscanners] Re: dpi - formerly PS sharpening

["bob frost" <bob@frost.name>]

Laurie,

I don't want to get into an endless argument over niceties of linguistics
either, but I still maintain that there is a real difference between the
'things' that define the image size - call them dots, pixels or samples -
and the drops of ink that an Epson printer squirts onto the paper which have
nothing to do with image size.

If 'dpi' is used for everything, then when I send an image with 256 dpi to
my printer, the printer converts it to 720 dpi in the driver and then prints
it at 2880 dpi in one direction and 1440 dpi in the other (using a most
recent printer as the example). Does this make sense to you?

Is it not more meaningful to say instead, that I sent an image with 256
pixels per inch to the printer which upsampled the number of pixels to 720
pixels per inch (its native image resolution) in the driver, and then prints
it using up to 2880 ink dots per inch horizontally and 1440 dots per inch
vertically (its real ink-drop max resolution)?

An image 'unit' - call it what you will - is NOT the same as a printer
ink-drop, and the resolution of each is a completely different parameter.
One resolution is the number of units per inch making up my image in PS and
the resolution of the upsampled image in the printer, the other resolution
is the maximum number of ink-drops that can be accurately squirted onto
paper by the printer to represent those image units. The latter resolution
is even different in two dimensions, whereas the former is the same.

Epson prints are made up of millions of ink-drops that look like DOTS. The
only DOTS in my images are the dots of red, blue and green phosphors on my
monitor screen, and their resolution is completely different again to that
of my image!

To call them all dpi seems to me silly when we have words that already are
in common usage and which describe them properly so that there is no
misunderstanding what one is talking about. Just because some people who
don't know better, and some that should know better, misuse technical terms,
does not mean that we should all fall in and misuse them. Education is
partly about learning the correct terms for things that need to be
distinguished.

I will say no more, but will continue to try to educate others to use
terminology that distinguishes between the resolution of images, monitors,
and printers.

Bob Frost.

----- Original Message -----
From: "Laurie Solomon" <laurie@advancenet.net>

>If you are going to use dpi for ppi, what are you going to call the real
>printer dpi? It's got to be called something different because it IS
>something different.

I am afraid I cannot take the above statemetns seriously.  There is no
"REAL" printer dpi and the difference is only a trivial difference just as
the difference between Kelvin, Celcius, anf Fehrenheit is or the difference
between meters and yards is.  It reminds me of the argument of an old lady
from Indiana who wrote the newspaper a letter to the editor against daylight
savings time arguing that we should not mess around with God's time.  Please
package up and send me 1 pixel, 1 sample, and 1 dot along with a point; and
while your at it, send along the precise dimensions of that unit of measure.
How large is a point, a dot, a pixel, a sample in order to be a point, a
dot, a pixel, a sample, and not something else?

Finally, I am responding to you in the spirit of friendship and not to put
you down.  I understand what you are saying and often follow a similar
course of action in my remarks to posts on lists; but when I do it is in an
effort to further the discussion of the substantive issues and not to
resolve terminological disputes or divert the discussion to a linguistic one
in itsown right.  In my response to Austin, I was not trying to take him to
task because I disagreed with him but because I felt the converstaion would
be diverted to a superficial issue.


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