Camera Labs

Hehe, yeah, when the step-up ring's on the 18-200mm

I bought the step-up ring on ebay. I don't think it matters which you get, just make sure it's metal and not flimsy plastic

As far as I can see, the step-up ring has no effect on vignetting. As I shoot RAW I correct them all in DPP anyway, but I can't say the vignetting is any heavier

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Canon DSLRs: 5D Mark III, 7D
Canon lenses: 17-40/4L, 24-105/4L, 24/1.4L II, 50/1.4, 85/1.8, 100/2.8L Macro, 70-200/2.8L IS, 100-400L
Other stuff: Canon 580 EX II, Canon 430EX II, Velbon Sherpa 600R
Apple: MacBook Pro 15", iMac 27", iPad III, iPhone 4S, Apple TV

My deviantART