Will changing the DPI affect video quality in any way - even theoretically?

Question

I have a Dell ST2220 display. It is a 21.5" display with a native resolution of 1920x1080.

At native resolution, the text and other visual elements are small due to it being just 21.5" across diagonally.

I could decrease the screen resolution to, say, 1600x900 at which point things onscreen become big enough for comfortable viewing. But when playing movies, I want the resolution to be at its native value so that there is a pixel-for-pixel match - instead of downsampling.

So I have decided to increase the DPI instead. At 120 dpi things are good.

At this DPI, will video playback quality be affected in any way?

I am guessing the screen is still running at native resolution, only somewhere inside, some rendering code is drawing icons and text a little bigger. But does the same happen for videos? Will video rendering also be affected? Or will videos be the EXACT same as it will be at 96 dpi?

I am using Windows 7 Ultimate.. if it means anything.

P.S. For those of you who might be thinking of the reply "Set it at 120 dpi and if you don't notice anything bad, just stick to it",... I am a perfectionist :P I can't sleep when I have even the most remote doubt that something is wrong, though it is not visible :D

Answer 1

No.

Rasterized images (such as .jpg files and pretty much every video format out there) store their data solely as pixels. They neither know nor care about real-world measurements like inches other than, possibly, an EXIF tag in the header which records the intended display DPI.

Similarly, monitors display only in units of pixels. If you're displaying a rasterized image on a raster device (like a monitor), then it's a direct pixel-by-pixel mapping. DPI only comes into play when you need to map real-world measurements into pixels. (e.g., Ten points is roughly 0.14 inches, so a 10-point font will use the DPI setting to figure out how many pixels that should be.) So long as you're working entirely in pixels, DPI is completely irrelevant.

Answer 2

I assume you've used Display Properties -> Advanced -> General -> Display to set the DPI.

On that dialog it states:

"To change font sizes only, click Cancel and go to the Appearance tab.

On that tab you can set the "Font Size" to "Large" or "Extra Large".

This will increase the text without affecting the DPI and thus remove your worry about the DPI (not that it would affect the video playback anyway).