Hey all you wallpaper geeks, here is a reason to make your wallpapers in PNG format and not JPEG:
From Shawn's newest tutorial: Desktop Wallpaper JPEG Quality Reduction - Disable in Windows 10 - Windows 10 ForumsInformationWhen you set an image as your desktop background wallpaper or slideshow, Windows will import a copy of this image and store it as the TranscodedWallpaper file in the %AppData%\Microsoft\Windows\Themes folder. Your desktop background wallpaper is loaded from this TranscodedWallpaper file cache.
If you select a JPEG image as your desktop background wallpaper, then Windows will automatically compress and reduce the quality of the imported copy to only 85% of the original JPEG image quality. This is done to help save disk space, RAM, and improve the performance of Windows while showing the desktop wallpaper image or when cycling wallpaper images during a desktop slideshow. Of course, the JPEG desktop wallpaper will not look as good as the original.
If you have a decent performing system, then you may wish to disable this automatic quality reduction of JPEG desktop wallpapers to have the imported image show with the full quality as the original JPEG image.
This tutorial will show you how to enable or disable the automatic import quality reduction of a JPEG desktop wallpaper for your account in Windows 10.
If you use a PNG image as your desktop background wallpaper or slideshow, then you are not affected by this automatic quality reduction since it only happens to JPEG images.