Summary: I have wanted this lens for over 2 years but couldn't afford it. Got it and although I'm a novice, I can see the improvement in pictures - it is amazing. I can crop pictures with better clarity and printed on Red River photo paper - WOW. No regrets and although it was used - it was in mint condition. Wish I knew more about specs for the real photographers out there - but to an untrained eye - it is a great buy.
Summary: Got the EC-20 mainly for telemacro photo. Even if not specifically stated by Olympus, it works well with the 50mm F2.0 macro lens as well. I tested it with the 70-300mm tele lens, and the results are good. Besides the 2-stop that you lose anyway, no major drawback. Resolution will get a bit worse, but again, any lens you add brings additional distortion and quality loss.
Summary: I love this product. Never had an issue with focus. With all the photo retouching software out there its no problem if you loose 1 f stop. Just make sure you use a mono pod or tripod and there is no problem.
Summary: This product exceeded my expectations. It is very well built and works well with all Zuiko lenses I have. (50mm, 12-60mm, 50-200mm 70-300mm). In certain low light conditions, naturally, auto focus is problematic, but also depends on the equipment used. It works perfectly with fixed aperture lenses, placing the camera in the form of priority in the opening, as the 500mm mirror lens I have. Perhaps it is expensive but gave a new spin on how to use my lenses.
Summary: I've had this converter for two years now and have found it very useful for zoo and wildlife photography. This trick to this teleconverter is that you need bright light because of the loss of stops. I use it with my 50-200mm and find shots in bright light to be crisp and sharp even handheld. However, when the light is not good the shots can be soft. This is why I did not give it 5 stars. Overall, it's a great deal for long range photography.