Focus distance settings- Canon 70-200 F4

[Mossberg]

I have purchased a Canon 70-200 F4. It has two focus settings, 1.2m to infinity and 3m to infinity. A Google says focusing is quicker on the 3m setting.

So, from your experiences, where does the 3m setting really make a difference?

I am trying to learn and understand my gear, so your input would be appreciated.

Many thanks

 

[Gav.]

Focus speed is the same regardless, but setting 3-Infinity will 'speed up' focus because it'll stop it from hunting in the close range of 1.2-3m when trying to find the subject when focus is lost.

for work over 3m away use the 3 and over setting but don't forget to switch it off as it can be annoying if you forget for closer focusing.

 

[Mossberg]

Thanks Gav. That makes sense!

 

[sk66]

It really has to do with depth of field. At longer distances the depth of field increases, which means there is more that is within acceptable focus, and less focus shift is required for actual sharp focus within that zone.

The switch should be labeled "full" (1m - ∞) and 3m - ∞. Which doesn't seem like much difference; but if you turn the focus ring you will find that the travel between 3m - ∞ is only about half of the total focus travel. So focus travel will be 2x as fast when limited to that range.

But IME it seldom makes any difference. It only makes a difference when the camera has absolutely no clue and wants/needs to search the entire focus range. And if you find yourself in that situation there are other more important/better solutions to attempt.

 

[Mossberg]

Thanks sk66. Some of what I enjoy is catching a bird in flight, so reducing that focus range is likely to make a difference. I know this isn't the ideal lens for that application, but its the best I have for now - and occasionally you are blessed with an opportunity!

 

[sk66]

Thanks sk66. Some of what I enjoy is catching a bird in flight, so reducing that focus range is likely to make a difference. I know this isn't the ideal lens for that application, but its the best I have for now - and occasionally you are blessed with an opportunity!

Then one of the main things to do to prevent hunting is to pre-focus at the expected subject distance. But error towards the short side; the camera (almost?) always focuses far before it focuses near, primarily because it is faster/easier (the DOF thing).

 

[Mossberg]

Thank you sk66, I will remember that!