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Leica50mm

Does auto focus make any zoom parafocal?

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I was thinking about this the other day.  . I have the canon 1DX mkii and canon zooms . It seems like the auto focus would keep focus through out the zoom .  I tried it and it works .

Why wouldn’t it? 

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Well... I think it would depend on the lens and the AF system.

I am not particularly familiar with Canon bodies and lenses. My understanding is that the 1DX II is one of their top of the line cameras. So that might have something to do with it.

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it doesn't make it parfocal, since that is, by definition, that the focus doesn't change when you zoom. But the focus does change and it is corrected by the focus. 
Sony got an interesting solution with the 18-110mm f/4.0 too, where the focus element is moved to correct. The problem with such electronic solutions is, that fast zoom movements can be too fast to correct and that you can't use those lenses on another non supported mount via adapter

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1 hour ago, Leica50mm said:

I was thinking about this the other day.  . I have the canon 1DX mkii and canon zooms . It seems like the auto focus would keep focus through out the zoom .  I tried it and it works .

Why wouldn’t it? 

A short zoom i did in this video

 

 

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1 hour ago, Leica50mm said:

I was thinking about this the other day.  . I have the canon 1DX mkii and canon zooms . It seems like the auto focus would keep focus through out the zoom .  I tried it and it works .

Why wouldn’t it? 

Works great with the C300ii and a 70-200 as well. 

You could say it performs as if it is parfocal, but there are situations where it won’t work 

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The problem is how fast and how smoothly the focus mechanism in the lens can track focus, which is both: working out if focus is lost, which direction to go to find it, and by how much; and also being able to actually change the focus fast enough.

The other method is to analyse the lens ahead of time and store that data, in which case you don't need to assess how focused anything is, you just get a zoom reading from the lens and compensate.  The XC10 does this, with its fixed 24-240mm equivalent lens.  Unfortunately I found in real life that if you zoomed quickly it wouldn't be able to keep up, and also it wouldn't reacquire it through the lens data, but would require the focus mechanism to do it's thing.
If you zoomed slowly then it worked though, so that was nice.

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