Notes on Image Quality

Retina displays

Retina displays have twice the pixel density of traditional displays, allowing for finer details to be shown. This in turn requires larger desktop pictures.

Some common (2017) retina display sizes are:

System Preferences and macOS will normally report the (lower) resolution size as the display size. This may seem somewhat odd, but reflects the physical amount of space available for the UI (User Interface) which is the same for both retina and non-retina displays.


Generally Avoid upscaling images. A desktop image should ideally, be at least the same size (in pixels) as the display (or displays) it is intended to cover.

Small upscales (10–30%) will often look ok.

Some images you'll find will likely already have been upscaled making them bad candidates for future upscaling. Such images will typically lack crispness and instead look blurred or smudged.

These are sometimes the result of sites trying to be helpful by supplying the image in multiple resolutions, even when this means excessive upscaling. They can also be found on forums and on image boards, where people have tried to make small images work on much bigger displays.

Image compression

Some image formats like jpg are lossy, meaning that higher compression rates leads to smaller files but also to more visual artifacts as some of the original image data is discarded/lost.

Be wary of overly compressed images, such images will often look grainy or pixilated due to their compression artifacts. Upscaling them will typically make this even more apparent. Some image hosting services (e.g. re-encode uploaded images aggressively, to save on storage and bandwidth costs.

Also note that lossy images get worse if they are re-encode multiple times, this may happen when:


For the best image quality, download directly from the artist or official site. Use a reverse image search to track down unknown artists and sources.