Question about 70-200 mk ii

friesianfan69

friesianfan69

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Donna
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I recently finally got my canon 70-200 mk 2,
Wow!! Love it.
But I have a question!
Probably dumb ones but anyway.
On the side it has 1.2mm or switch over to 2.5mm, what is the difference and what do they both achieve?
Thankyou
 
Well the camera will focus from 1.2m to infinity and 2.5 to infinity.

If for instance your camera is set at 2.5m then anything before that the lens will hunt and not achieve focus.

If at 1.2m and you're shooting something past 2.5m then the lens will still get focus but the image may not be as sharp.

Here is a better explanation

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.


And it's not millimeters it meters. :)
 
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da_nige said:
This bit isn't true I'm afraid. The image will be just as sharp once focus is achieved it will just take longer to achieve focus.
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Ok makes sense as i shot a pic that came out clear passed that distance.

 
da_nige said:
This bit isn't true I'm afraid. The image will be just as sharp once focus is achieved it will just take longer to achieve focus.
Click to expand...

Talking from personal experience. Didn't find it as sharp but thanks for the correction.
 
Personal experience. Shooting and missing focus. No big issue haha
 
Jayst84 said:
There is no difference in the performance of the lens, literally nothing changes in the optics, so sharpness will be the same..........
Click to expand...
Despite there being no change in the optics, the sharpness isn't only limited by the optical performance of the lens.....focus accuracy plays a big part too.

LBJNBA said:
Personal experience. Shooting and missing focus. No big issue haha
Click to expand...
Statistically I believe that your experiences would be correct.....ie, focusing from within the focus limiter can provide a greater degree of sharpness based on the average of multiple attempts.

When using a lens with a maximum aperture of >/= f/2.8 and a focus point optimised for f/2.8 then the body's targeted plane of focus will be within 1/3 DoF. Modern bodies are extremely good at viewing a blurry, out of focus projection and deciding what command to send to the lens to achieve a good image. If this command results in a position that is within 1/3 of DoF then the shutter can be released.
If the lens is already closer to the required focus position (as would be the case shooting a close subject with the limiter engaged) then the body has more tangible detail to use in its calculation and, statistically, it may well arrive closer to the plane of sharp focus.

Bob
 
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