Canon 70-200 f4L IS unusable at f4

sobrien wrote:

I believe this is a known issue with some copies of this lens. My first copy, at least, had similar problems at F/4 - I could see a very significant improvement stopping it down to F/5.6. The discrepancy seemed to be most pronounced at infinity/relatively long distances. I spent a long time making sure that it was not a AFMA issue and also checking online reviews that showed the difference in sharpness at different apertures and focal lengths. As soon as I tested out a different version of the lens, however, I knew immediately that mine was not functioning as it should. Really, the difference in sharpness between F/4, F/5.6 and F/8 is very negligible. I honestly doubt I would be able to tell the difference, even looking at 100% view, in many instances. So I sold my first copy (with full disclosure) and bought another copy that is extremely sharp at F/4 at all focal lengths. Autofocus is really reliable too. This lens really is as good as everyone says. And I love how lightweight it is considering the quality it produces. Works great with the 1.4 extender too. I would never consider buying the F/2.8 version unless perhaps if I was to become a pro wedding/event photographer.

Best of luck!

Shane

I should add that my first copy was a good few years old. My existing copy is only a couple of years old. So it could be that it is an issue that (i) is more prevalent in older models for production reasons etc. or (ii) happens over time. I am hoping that it is (i) as the prospect of my new lens losing its edge over time would be disappointing. Time will tell I suppose.

Unfortunately I do not know enough about the issue to know if it is repairable or what that would cost.