260f542b__to_Good_Practice__RasterImg_2__Recommendations
[Format] .png [Properties/Technologies] Portable Network Graphics, an ISO standard and supported by the W3C[3] [Description] Intended as a replacement for the GIF format, PNG offers 32-bit colour depth, lossless compression, support for an Alpha channel (transparency) amongst a host of other features. PNG does not, however, support standard EXIF metadata and, as the format was primarily designed for internet use, it does not support colour spaces other than RGB. [Recommendations] 
PNG has become the format of choice for lossless presentation. Although TIFF is the preferred format for long term storage of images, the PNG format offers a number of features and should be used in preference over the GIF format where possible e.g. where lossless compression is required. While the format offers certain advantages over JPG (e.g. less visible artefacts) it is not recommended for use with digital photographs.
Guides to Good Practice: RasterImg_2
Recommendations