TR Forums

I just picked up these from eBay. I figured that for $20 it's probably worth the trial. Anyone have any experience with these things?

Diopters can be good. Cheap ones are somewhat hit and miss. They reduce the effective focal length and working distance, and work better on long focal lengths. John Shaw's book Closeups in Nature has a lot of information. Google took me to where he discusses using diopters on a 50mm lens. In summary, a +10 gets you to 1:2 magnification and lowers your effective focal length to about 33 mm. That gets to be a bit difficult to deal with as working distance becomes really, really close. My cheapo macro came with a diopter to get to 1:1 but I normally use tubes instead.

I bought some of those for really cheap. You can see some samples I posted in this topic.
Considering the price I payed for them, I'm fairly satisfied. The main drawbacks for me were loss of sharpness (especially off-center), loss of contrast and heavy colour fringing.