figuring out acrual DPI of images in pathfinder vs photoshop

[Sossity]

I was looking at some images in both pathfinder & Photoshop CS6, when I looked at an image I scanned with my HP photosmart, in the get info button in pathfinder, it would list horizontal & vertical resolution as 600 DPI, when I opened this same image in Photoshop, & clicked on file info there was very little about it under camera data, just a resolution of 72 DPI.

In the HP scan settings, I chose 600 DPI, why is Photoshop showing it as only 72 DPI?

what is the actual resolution of this image? which is going to give me an accurate number and the one I should believe? pathfinder? or Photoshop? I thought it was 600 DPI

how can I be sure that I am scanning my images at the resolution I choose?

 

[MisterMe]

DPI is meaningless except in a displayed or printed image. A 300 dpi image printed at 5 in x 8 in will be only 150 dpi if printed at 10 in x 16 in. For electronic images, the meaningful number is pixels. In the case of the 5x8 image here, the pixel density is 1500x2400. You need enough pixels for your final product to have the desired resolution.

The desired resolution is determined by how the image will be used. If a color image is intended to be held in hand, then it will have photographic resolution at 300 dpi. If it is to be used as a poster on the bus stop cover, then its resolution need by much lower.

These are issues that have been discusses ad nauseum on this and other forums. A simple search of this forum will yield quite excellent discussions of the issues surrounding the proper resolution for your application. There is no need to repeat these discussions in this thread.