# canon 70-200 2.8 is 2 - 1.2m/2.5m focusing distance switch



## bobby samat (Oct 28, 2014)

there is a switch on the 70-200 2.8L's that says 1.2m to infinity or 2.5m to infinity. i understand that this switch determines the closest possible focusing distance for the lens.

aside from the closest focusing istance, what else changes when you switch between 1.2 and 2.5? battery use? af speed?


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## Mitch.Conner (Oct 28, 2014)

Nothing as far as I understand.

It's to prevent you from autofocusing on the wrong subject in contexts when you only have a moment to get the shot, like sports.

That's my understanding of it at least.


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## privatebydesign (Oct 28, 2014)

All the focus limiter switch does is limit the range the lens will look for focus in. Some lenses, like the 100L Macro, have low range options too. So 'Full' or 1.2-∞ wlll allow the lens to hunt for focus across it's entire range. 

With the 70-200 f2.8 IS MkII if you choose 1.2-∞ then the lens will try the entire focus range to find the closest subject, if you put it in 2.5-∞ then it will ignore the range 1.2-2.5, this might not seem much but if you look on the barrel it is a long throw and it takes longer to go from 1.2-2.5 as it does from 2.5-∞. The only point is to speed up focus acquisition, particularly when you lose focus completely and the camera AF hunts to look for the subject.


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## neuroanatomist (Oct 28, 2014)

Primarily the MFD. But secondarily, if the lens needs to rack through the full range to find focus, restricting the range speeds that up (the focus movement isn't linear, going from MFD to 'near' is similar to going from 'near' to 'far' in terms of focus element movement, but focus distance changes 1-2 meters for the former, but 10s of meters for the latter.


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## bobby samat (Oct 28, 2014)

makes sense. thanks guys


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