bokeh that the diopter produced. Since I had been having problems with isolating the subject in the areas where I shoot, and I hate spending time in Photoshop doing things with the computer that I could be doing with the gear, I decide to give the 500D a try.
Mark, as usual, was right -the bokeh is excellent!
The 500D does take a little getting use to. I don't think that it gives me less depth of field, but it seems to compress the area of focus in the sense that a scene goes from being in sharp focus to being completely out of focus over a shorter distance. The area of sharp focus is the same as not using it, but the area between sharp and blurry is reduced -if that makes sense. Take a look at the background in the image with this post. I shot that female Violet Darter in a peach orchard, but all you see is s diffused sea of green due the way the 500D smoothes out the background.
There is no loss in image quality -period.
The 500D is designed to correct for chromatic aberration and it helps to keep the image circle sharp and, unlike an extension tube, there is no loss of light. The magnification that I get with the diopter is almost the same as a 25mm extension tube (1.375x for the 500D verses 1.39x for the 25mm tube). Given the choice between using the 500D and a teleconverter I'll take the diopter. But there is one problem...
Don't use a teleconverter with the 500D.
Stacking tubes between the camera and the lens with the 500D is no problem (all of my recent shots above 2x were taken with the diopter and tubes), but I wouldn't recommend using a teleconverter with the diopter -way too much glass and there is no increase in working distance.
I've had the 500D on the end of my 100mm macro lens since I've bought and only took it off once to shoot some bees in flight...