I'm trying to understand how to deal with what I think is a rather confusing inconcistency between the system resolution PPI of Windows and what is the PDF reader settings, in this case I'll speak about Adobe Reader, though I've faced the same issue also with Sumatra PDF reader.
Basically what I'm experiencing can be reproduced with the following steps:
- Get/create a picture of any size, let's say for ex. 900w x 650h pixels
- Convert the image to PDF (via either Acrobat, Photoshop, ImageMagick, w/e)
- Open it in a PDF reader at "Actual size" or 100% zoom view
Now if I compare the opened PDF file with the same image opened from an image viewer, be it Irfan, windows default app or else, I see that the displayed "Actual size" of the PDF file is roughly 1/3 bigger than the normal image displayed in the image viewer, resulting in a stretched pixelated image. To be correctly displayed the image as intended I have to set the PDF reader to a ~66% zoom.
This is, I think, due to a weird inconcistency between what the PDF reader see is the current system resolution (in my case Windows 7) of 96ppi. If I change Adobe Acrobat display setting to a custom value of 72ppi, the image is correctly displayed at 100% zoom, just like in the image viewer program.
Windows “solution” to this problem
The Windows solution was somewhat controversial. The decision was made to report the resolution of displays on Windows as about 1/3 greater than actual resolution. This roughly corresponds to the increased reading distance. So, for displays around 72 PPI, Windows would indicate 96 PPI. When IBM came out with the 8514 display, which was around 96 PPI, we added a new resolution for 120 PPI.
I’m not sure about other potential solutions that were investigated—like some type of a zoom factor, but the solution chosen was quite easy to integrate into the system.
I don't know if this is the cause, but fits pretty well.
Why is this happening? Can you reproduce the same issue or is an isolated case on my machine?
What should I do to make it sure that if some user view a PDF at 100% it's displayed at the intended resolution? (the same he would see if he opened the same image file in a image viewer application)
NB. I can't avoid to use PDF files, so using a normal raster image is not an option.