Soft Macro Pictures with Canon 20D and 60 mm EF-S

I read this site's article on diffraction which was very interesting and I think explains the problem I am having but I wondered if I could be advised on this further?

I have been taking macro pictures with my Canon 20D and EFS-60mm lens and a MT-24EX Twinlite (hand held). I have taken shots at a range of apertures such as f4, 14, 22 and 29. I was really surprised to find that ALL my shots taken at F22 or higher were much less sharp when viewed at 100% crop (compared to the wider aperture pictures) , considering also that the flash did seem to provide adequate lighting.

Just to check I did a test when I took pictures at F22 with and without a tripod and this made no difference, all the pictures were unsharp at 100% crop..

Would you agree then that this is in fact diffraction? I was surprised that I saw such a noticeable effect at F22 and I was wondering how close-up photographers manage to get a good depth of field but still have good image sharpness?. This seems impossible with my set-up.

Any advice would be appreciated.

That is most certainly diffraction, which at f/22 is very pronounced on the 20D.

Thanks very much for your help. I have just one more question then. Is the 20D known to be particularly bad for diffraction? I'm planning on getting the 5D, will I have less of a problem with that camera?

Diffraction is a fundamental limitation of any optical system, regardless of camera type. The 5D has slightly less diffraction at a given aperture, but it also requires smaller aperture openings in order to achieve the same depth of field-- so the two effects pretty much cancel and it is overall no better or worse. You will, however, require longer exposure times for a given depth of field and ISO setting...