Setting the resolutions array is one way to specify the number of zoom levels. Let's see it in action.
In the map object definition specify the resolution array as the following:
map = new OpenLayers.Map('map_element', { resolutions: [ 1.40625,0.703125, 0.703125, 0.3515625, 0.17578125, 0.087890625, 0.0439453125 ] });Zoom around on the map. Because we've only provided five possible resolutions, you should be able to zoom in five times.
Using the resolutions array, we were able to specify the number of zoom levels. Unless we're using a cached tile service, this isn't necessarily the easiest way to specify the number of zoom levels. We have mentioned earlier we can also use scales, and we can also use minResolution and maxResolution.