As discussed, source images uploaded into Image Manager will be used to create the actual images used by your site. As such, the quality of the source images will impact how images will appear on your site.
Image quality is a complicated issue and depends on many factors including the dimensions of the image (pixel by pixel measurement) and the pixel depth (also known as dpi). The filesize of an image can be an indication of an image’s quality. For example, if an image is 400 x 600 pixels and the filesize is only 30kB (kilobytes), the image will likely not be of good quality. It may be fine for display on the Web in its native form, but it will likely not be a good source image from which to create other images of different sizes.
A digital camera may produce an image with a filesize of over 1MB and dimensions 1600 x 1200. A more sophisticated digital camera may produce an image with dimensions that are 5 times this large and a filesize approaching 50MB. Neither of these images in their native form would be suitable for the Web. However, the 1MB image may be a perfect source image from which Image Manager can create all required versions of the image for your site.
Note: Image Manager may have difficulty loading extremely large images. You may encounter out of memory errors. The maximum file size of a web friendly image should not exceed 700kb.
A more complete discussion on image quality could easily extend across many pages. The purpose here is to provide a high level discussion that will provide the background required to work intelligently with Image Manager. A good rule of thumb is that it is always best to start with higher quality (larger dimension) images and let Image Manager take the quality down to make your images “web-ready”. Starting with lower quality images will create grainy and unappealing images. The best way to learn is to test your images out in your Staging environment.
Regarding file formats, the two most common formats in use on the Web are JPEG (Joint Photographic Experts Group) and GIF (Graphical Interchange Format). JPEGs are excellent for photographic images, but will generally not work as well for graphs, charts and explanatory illustrations because the text may appear fuzzy, especially at low resolution. GIFs will be more suitable in these instances.
Image Manager can also accept TIFF (Tagged Image File Format) and will convert to JPEG. TIFF files are usually very high quality with high DPI and are generally used for hardcopy print work (e.g. brochures).