Using Wide Angle Lenses for Close Up Photographs and the 250D Close Up Filter
Wide angle lenses can give neat wide distorted close up views with a lot of Depth of Field. For example with a 24mm lens everything 8" away at f/22 is in focus. With a 35mm lens everything 12" and farther at f/16 is in focus.
The Canon EF 17-40mm f/4.0 L USM can focus at 11 inches and has a magnification of 1:4 or 1/4X at 40mm with the 250D, the 500D will magnify up to 1/5X. Zooming out to 17mm at this distance gives a dramatic perspective. Adding some extension tubes shortens the closest focusing distance and gives macro world views. A 12mm tube gives about .8X and a 25mm tube gives 1:1 magnification.
Use the 250D Canon two element close-up filter with wide angle lenses to get even closer focusing and more magnification. Using a 250D can increase magnifications also by about 30% for most wide angle lenses.