hi i use paint shop pro quite often and have recently noticed the
(pixel per inch) ppi is only 72 on every photo i have taken with my
a80. anyone know why? is it the software reducing ppi?

The image from the camera does not have any 'ppi' at all. It is simply
a 2000 x 3000 or whatever pixel count the camera sensor delivers. It is
a dimensionless collection of pixels.

However, when the image is opened in a graphics program, in order to
display the image, the program will use a default ppi. It is the
graphics program which does this, and not a feature of the image
itself. If your graphics program has an image size function, you can
alter the ppi *without* resampling, whereupon the image size changes.
F'rinstance, if your program defaults to 72 ppi, and the image size is
2000 x 3000 pixels, the apparent size on the screen will 2000/72 x
3000/72 inches, that's 27 x 42 inches approx. Which is why you can't
see the whole picture at once. If you tell the program to display the
image at, say, 600 ppi, the image will then be about 3 x 5 inches *on
the screen*. The image itself hasn't been changed at all, only the
pixel display pitch has changed.

The same goes for printing. Specify a size for printing, and the image
delivered to the printer will be at such a ppi as will give the required
size.

NOTE none of the foregoing has resampled the image. If you want to
send a picture over the net, at a given size, say, 5 x 7, at 72 ppi,
then you will have to resample, that is, change the pixel count so that
the image at 72ppi will produce a 5 x 7 image on screen. Now, a 5 x 7
image at 72ppi will be 5*72 * 7*72 pixels, that is, 504 x 360 pixels,
which is an image of 181,440 pixels (far smaller than the 6 million
pixels in the original image. Inevitably, you lose information when you
do this, so don't do it to your original image!!), and a Jpeg file with
about a 10:1 compression will be about 18 kilobytes, a suitable size for
sending over the net.

Hope this helps,

Colin