Checking for 4K upscales

DroneSmelter · April 24, 2015

Hi! Does anyone know how to check if an image is truly in native 4K or just a 1080p upscale? I need to check this photo in particular:

Thanks to anyone who can help in advance!

manikyath · April 24, 2015

i'm by no stretch of the imagination a photography expert, but something that caught my eye was that for some reason when i zoom in extremely closely i see "squares" pop up in the pixels, then i checked a random high-res photo i pulled from my HDD to see if it'd do the same, which it didnt.

i did a quick attempt to try and reproduce the squares in a different picture, but however much i stretched and unstretched, i cant seem to produce a similar effect.

pic as reference: (left = my random picture that is from a professional camera, right: yours)

http://puu.sh/hpmIz/17ca24c9e0.jpg

the left is a *random* mess of pixels

the right seems to be an orderly pattern of squares, or at least much more noticable...

could some camera folks explain to me what i'm seeing, i'm kinda puzzled myself.

DroneSmelter · April 25, 2015

the left is a *random* mess of pixels

the right seems to be an orderly pattern of squares, or at least much more noticable...

could some camera folks explain to me what i'm seeing, i'm kinda puzzled myself.

Yeah, I've noticed that too and even counted the pixels, the "squares" all seem to be 16x16 pixels. I would immediately know that it's an upscale if the squares were all 4x4, because if you upscale a 1080p image to 4K to get a 1:1 image with no aliasing you make one pixel four pixels. But yeah, I still don't know the answer to my original question unfortunately.