About Photos for the Wiki

There are several issues involved in preparing photos for the Web.  The most important is file size, because large files slow down pages which can lead to partially downloaded photos, especially for users on slow connections or shared networks.  The available options will depend on which software program you're using.  To complicate things, different programs (see How to Prepare Wiki Photos for some details) generally have different methods/steps for optimizing file size & achieving the most Web-compatible physical dimensions.  All of which is generally quite opposed to what is required for quality printed photos.

The primary issue is resolution.  Good print quality requires 150-300ppi (pixels per inch), which results in very large file sizes.  But on the Web, because all monitors — regardless of type — can only display 72ppi, those large resolutions are wasted & just weigh/slow things down. A lot.  Depending on which software program you're using, reducing resolution to 72ppi will also automatically reduce file size. But that's not the whole story, because that process will also reduce actual physical dimensions (width & height) as well as image quality.  The real trick is to do the one without reducing the overall dimensions and quality too much.

Image quality options can be as crucial as resolution. Because the JPG format was developed as a method of compressing (i.e., reducing) digital bits/bytes to optimize file size, each step down in quality (from maximum to high to medium to low) actually loses data as well.  This is why once you've saved an image with a reduced resolution & size, enlarging it looks fuzzy. Image details have been literally deleted, with the result of a great deal of pixelation and a degraded image.

In addition, the following image manipulations will increase file size, because each adjustment adds digital information to the file: 1) high contrast; 2) increased sharpening; 3) extreme brightening/darkening; 4) intensified saturation/hue.