Render size versus saved image size

I rendered an image today, and after saving and opening for some postwork, I noticed it was a little smaller, and not as clear as what showed in the render panel. I restarted another render to grab the snapshot below to show the difference. The render was set to 1536x2048
Any thoughts? (there is no zoom on the ifranview image, as can be seen its 100%...I confirmed the size with paint.net)


RenderSize.jpg
1621 x 1003 - 477K
Comments
Have you tried another viewer, such as the built-in Windows viewer/ it does sound as if it is being resampled by Irfan View.
Hmmm...in Paint.Net, Irfanview and Microsoft Paint, they all open at 100% in the smaller size. In Chrome, Windows Photos and Daz Renderer it shows the bigger size.
What is that about?!
Odd. In an illustration type package 100% doesn't usually mean 1:1 pixels, but I'd expect a bitmap type application to use 100% to mean 1:1.
I have the same effect and it's due to Win10 display settings (see attached pic).
DS App follows the OS setting and thus is scaled 150%.
IrfanView picture display does not follow the setting and shows it on 100%.
If you scale it in IrfanView to the OS setting (in my case 150%) it is the same size.
Great find, thanks for pointing that out! :)
What does it say under the pixel size in IrfanView? It should be the same as the render pixels and should display as 100% or a lower % if you have it set to window size which is smaller than your screen size.