Does a 200mm lens with a 2x extender mean 600 mm?

Question: Does a 200mm lens with a 2x extender mean 600 mm!?

Hello friends!. I was looking at reviews of Canon 70-200 mm f/2!.8 IS lens!. Two people who wrote the reviews indicated that using a 2x extender, they didn't need a lens which could reach 600mm - which confused me a little bit!. I supposed the effective mm would be 400 mm!. Can you clarify if the lens would reach 400mm or 600mm!. Thank you Photography community!.Www@QuestionHome@Com

Best Answer - Chosen by Asker:

You are correct!.!.!.!. well sort of!. When using a 2x converter, that 200mm lens becomes a 400mm lens!. But you also must consider the 1!.6x sensor crop found on many Canon DSLRs!. You see, a 200mm lens is said to be 200mm on a 35mm or full frame camera!. However, cameras that have smaller sensors, like maybe the Canon XSi or XTi, will have a 1!.6x crop factor!. Basically, you multiply 400mm by 1!.6, giving you 640mm!. 640mm is what you'll actually be using, not 400mm!.Www@QuestionHome@Com

35mm sensor it would be 400mm

APS sensor it would be 600mm!.Www@QuestionHome@Com