Resolution, Pixel Density, and Viewing Distance

Physical size determines how densely those pixels are packed.

Pixels per inch equals the pixel diagonal divided by the physical diagonal. A 4K phone and a 4K television have the same pixel count but very different density.

A pixel covers a smaller angle as the viewer moves away.

Pixels per degree is a geometry estimate, not a medical threshold. Vision, content, scaling, contrast, and motion all affect whether extra detail is useful.

High density can make unscaled text physically small.

Modern operating systems scale interface elements while retaining rendering detail. Application behavior and multi-display workflows can influence the practical choice.

More pixels and frames require a capable end-to-end link.

Check the GPU, port, cable, dock and display for the required format. HDR certification is separate from resolution alone.