4K or 1080P TV for Still Images and 1080P Video?

[dharty]

I am going to buy a 55" to 65" 4K or 1080P TV to display sill images and use as a secondary monitor for video editing. I went to a store and compared two Samsung TVs with a JPEG image sized at 3840 x 2160 and 1920 x 1080 (I compared the Samsung 1080P, 60" 7150 TV and 4K, 60" 8550 TV using their USB input). The 3840 x 2160 file clearly displayed sharper on the 4K screen than the 1920 x 1080 file on the 1080P screen, as expected. Both TVs display 1080P video with similar quality, though the 4K screen was still slightly sharper even while upscaling 1080P video.

What was unexpected is that the 3840 x 2160 file displayed much sharper than the 1920 x 1080 file on the 1080P screen. Does anyone know why that would happen? A 3840 x 2160 image would not display sharper scaled to fit on a 1920 x 1080 computer monitor than a 1920 x1080 image file would.

Thanks,

Drew Harty

 

[Run&Gun]

What was unexpected is that the 3840 x 2160 file displayed much sharper than the 1920 x 1080 file on the 1080P screen. Does anyone know why that would happen? A 3840 x 2160 image would not display sharper scaled to fit on a 1920 x 1080 computer monitor than a 1920 x1080 image file would.

Thanks,

Drew Harty

To me, that's not unexpected at all. It's downscaling the image. You're taking an image that's four times as big as the native display and essentially squeezing it down to fit, so it's going to appear sharper. It's just like looking at high resolution(say 20mp+ from a 5D) still images on a computer screen and they look very sharp, but if you zoom in to 100%, they will not look as sharp. Or pictures you take on a cell phone viewed on your phone screen look great, sharp and in-focus, but import them into your computer and look at them on a larger screen and you see the imperfections of missed focus, etc.

 

[dharty]

To me, that's not unexpected at all. It's downscaling the image. You're taking an image that's four times as big as the native display and essentially squeezing it down to fit, so it's going to appear sharper.

I guess what I am not understanding is how a TV scales a still image. In Photoshop, if I take a 3840x2160 image and resize a duplicate file by 4x smaller to 960x580 (which deletes pixels) the smaller file appears similar on a computer monitor to the large file just rescaled (no pixels deleted) to the same display size. I assumed the same thing would happen on a TV but apparently not.

A TV must be scaling the image differently because a 3840x2160 image displayed on a 1080P TV does look sharper than the same image sized at 1920x1080, and also appears to have more edge artifacts than the same 3840x2160 image displayed at a native size on a 4K TV.