In jAlbum 13.7 we've introduced support for HiDPI images (See Settings->Images). By activating this option your images will look much sharper on HiDPI screens like those found on modern mobile phones and tablets. HiDPI screens are screens that have far smaller pixels than ordinary computer screens so they pack more "dots per inch" than ordinary screens (144 or more instead of 72). They are still not that common for desktop computers, but modern tablets and mobile phones have HiDPI screens to a high degree. As the viewing distance for these screens basically is half that of a desktop computer screen, it really matters whether your images are viewed in normal or HiDPI as can be seen here:
Album on mobile device. Normal dpi (click to view full album):
HiDPI images in jAlbum are essentially twice the pixel size in width and height. They therefore need more disk space and network bandwidth, but the size penalty doesn't have to be so dramatic as one can compress HiDPI images further without getting noticeable JPEG artifacts, this as the JPEG artifacts are now only 25% of their previous area. In these sample albums above I could lower the JPEG quality to 60% from 85% for the HiDPI album without any noticeable degration in quality. The resulting disk size went up from 0.46MB to 0.81MB, something I don't consider a problem in 2016. Just imagine how much disk space and network bandwidth has increased since 2002 when jAlbum was created...
If you don't want your albums to have this size penalty for sake of looking better on mobile devices, you can compromise and use HiDPI for thumbnail images only. After all, the thumbnail images are those who benefit most from this change. jAlbum gives you free choices, as always. For me, it's a no-brainer. I will use HiDPI images on all future albums. To update your albums, get jAlbum 13.7 and reprocess your albums with HiDPI checked under Settings->Images. HiDPI works with the vast majority of jAlbum skins.
/David and the jAlbum team