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 Post subject: aperture and focus
PostPosted: Wed Feb 15, 2012 11:44 pm 
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If I focus, then change the aperture, will the focus change and do I need to re focus?

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PostPosted: Wed Feb 15, 2012 11:48 pm 
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The focus point will remain the same distance from the lens, if thats what you're asking. The rest goes without saying - depth of field, accuracy, yadda yadda yadda...

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 Post subject:
PostPosted: Wed Feb 15, 2012 11:50 pm 
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Yes, changing the aperture without having to re focus.

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PostPosted: Thu Feb 16, 2012 1:09 am 
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Refocusing moves the plane of focus, changing aperture changes the depth of the plane of focus, but it doesn't move it.

So, changing aperture without refocusing (assuming no camera movement) will not change your focus.

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 Post subject:
PostPosted: Thu Feb 16, 2012 4:39 am 
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Potentially VERY wrong, guys!


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 Post subject:
PostPosted: Thu Feb 16, 2012 4:40 am 
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dubaiphil,
Can you explain why you think it is wrong?

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 Post subject:
PostPosted: Thu Feb 16, 2012 4:45 am 
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Some fast lenses in particular are known for something called Focus Shift.

A couple of classics that come to mind - Carl Zeiss 1,4/85 and 1,4/50, but more 'modern' optical designs can also exhibit this.

So stopping down from f1.8 to f.4 might not change your focus, but you might be equally out of focus! End result = blurry image anyway.


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 Post subject:
PostPosted: Thu Feb 16, 2012 4:48 am 
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I wasn't sure on this one, hence why I asked. :D

I am finding the primes and zooms work differently. Sometimes I get unwanted bokeh on the primes (numerically lower F stops), where's the zooms aren't as servere.

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