Canon EF 2.0 Mk III Telephoto Extender
To say I was apprehensive of purchasing this tele-converter would be an understatement. After owning the Canon EF 2.0X mk II and being completely disappointed and underwhelmed with it, it took me years to decide to try another 2x extender. After I did purchase it a few weeks back, it even sat in my bag a week or 2 before I decided to pull it out and try using it.With a tool like this, you want to use it for the right reasons and on the right kind of lenses. With that said, I'm using this on the Canon 300mm 2.8mm professional lens. Because the Canon 300mm has a smallish range, I've always shot with the Canon EF 1.4 MkII telephoto extender tacked on the back of it. The 300 is such a sharp lens, I lose very little sharpness using the 1.4 tele. Being a bird/wildlife photographer, I am always looking for more and more MM, so I decided to go ahead and try it.So far it's been everything I was hoping for. Much sharper than the 2.0 Mk II with the addition of new coating on the glass, this rugged and now very sharp tele didn't disappoint. Without doing any scientific study I would say this is at least 50% sharper, and at least that much better with contrast than its older counterpart.As always Canon L pro equipment is built like a tank, with dust proof and water resistant construction, it keeps up with the Pro L lens standard. The Mk III appears a bit smaller than the Mk II and the "white" coating has changed with the Mk III line of lenses, so the color is a bit different on the outside.Though I still have tons of shooting to do with it, so far I love it, and though it is high priced, appears to be well with it.As with any additional glass added to your lens, you really need to learn how to shoot with this tele. Forget hand holding it, use a tripod. Also because this is a 2X extender, you're losing a LOT of light. With my Canon 300mm 2.8, with the 2.0 mk III I'm now shooting at aperture of f/5.6. You're also losing a LOT of autofocus speeds. Canon is saying as much as 75%, but it didn't feel that high. So you need to use this lens in good to great lighting, on a tripod using already good Canon glass.Ricky