Help request

Well....yes....sort of....but not too bad once you get past the terminology.
DPI is used in a lot of places and means differing things...that is the
confusing part.

Your camera has photo sensors. The RAW data they take is changed to the
information in a TIFF and in this file format you can see the individual
pixels. (JPG introduces compression so won't be addressed here)

Now we are at the first part of your question. We have pixels and they are
just data that we cannot see...hold a cd up to the light for a look if you
don't believe me. We need to print to something to see the data. In pre-PC
days it was called printing even on a monitor....and it was...and is.

The monitor does not have pixels....it has lots of Red Green and Blue spots.
A group of these spots can be grouped together to make other colors....and
that is representative of the picture element....or pixel.

If you print to inkjet you do about the same thing. But this time the image
is sent to a printer and the RGB is changed to CMYK for use with 4 color
inks. Groups of little spots of ink are put together to form the appearance
of more complicated colors.

When we want to print using Offset Lithography we need to get CMYK dots
made too...like for the inkjet or monitor...but this time we need to get
them on a printing plate. Nowadays its done with lasers....hmmm....never
tried to explain this before....it makes sense in my head. If you had a 1:1
relationship of PIXELS to Offset Plate DOT then you are going from shades to
solids and ....no....damn....can't get there from here....What I can say is
that you want at least 2:1 PIXELS to DOT. Your commercial printer will tell
you how many dots he will use on a job depending on the paper and the press.
Newspapers uses about 85 dots per inch. That means you will need 170 pixels
per inch. Lines per inch usually refers to offset and I like to use it only
in that case to keep it separate from other uses of DPI....head
spinning.....that is all for now.


"Monte" wrote in message
om...
First you need to give us some details.
What camera do you have, how big the print must be and what is the
dimension in
pixels of your stored digital image

The camera is a Minolta 301 DiMage

I had to bite the bullet and send off the image without knowing what I
was doing. I resampled it to the 4X4 inch they wanted and 300 dpi.
They never complained so I think it was fine. I originally thought in
error that I could set the camera to a pixel size that equaled 300
dpi....

We should leave this stuff to the professionals

I don't understand the pixel to dpi conversion very well, it is
confusing.