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PostPosted: Sat Nov 20, 2010 12:17 pm 
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Joined: Tue Aug 31, 2010 8:23 pm
Posts: 126
Hi all
So ive been reading up on the hyperfocal Distance stuff.
I get the principal of it ok but how to apply it to good effect in real world situations.
Been looking here and using this calculator.

http://www.nikonians.org/html/resources/guides/dof/hyperfocal2.html

So for example, ive just picked up the Tokina 11-16mm f2.8.
If i set it at 11mm, f5.6 and set focus to 10 ft i should be good focus wise from 2.6ft to infinity as i understand it using their calculator?
Should i really convert the numbers to a 1.5 sensor crop factor of the D90 to get more accurate results, so 16.5mm in this case?

Is it best to manually focus using this technique as if you used the AF i guess you would have to focus on the ground or some object at the chosen focus distance and then lock it off.
Would there be from experience a good range of f numbers to stick to to keep other optical lens effects under control?
Cheers


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PostPosted: Sat Nov 20, 2010 12:48 pm 
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Joined: Sun May 25, 2008 12:48 pm
Posts: 8022
Location: UK
That calculator you linked appears to allow selection of DX/FX format so you don't need to adjust the lens focal length, it does it for you. It does change the field of view, and with certain assumptions, that will affect the apparent DoF and therefore the hyperfocal distance.

It's probably easiest to use the lens distance scale to manually set focus, as otherwise you'd have to measure and find something else to focus on for each shot.

If you want maximum lens quality, stopping down helps up to the point where diffraction starts to soften the whole image. Stopping down also increases your DoF too. Assuming you have a tripod or otherwise can take longer exposures, using around f/8 on crop sensors is a good balance, but down to f/16 is still decent if you need the extra DoF. The DoF also varies with the focal length, so you might find you need more or less depending on that also.

Do try it in practice and see if the results are what you expect. By definition, at the extremes the image wont be in focus, but only "sharp enough" within some considerations. Do juggle the variables if you're not getting what you want.

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PostPosted: Sat Nov 20, 2010 1:25 pm 
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Joined: Tue Aug 31, 2010 8:23 pm
Posts: 126
Hi again!
OK, l'll work a few variations at f8 to start with and see what i get.
Off on stomp about now with the camera before the light goes completely...
Cheers


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PostPosted: Sun Nov 21, 2010 6:02 am 
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Joined: Wed May 23, 2007 8:38 am
Posts: 357
Does your camera support live view and have depth of field preview button/function? I think the D90 does have both, you can use live view and then activate depth of field preview and zoom into see what foreground and background is in focus, better than a large format view camera!


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PostPosted: Sun Nov 21, 2010 11:48 am 
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Joined: Tue Aug 31, 2010 8:23 pm
Posts: 126
It does yes. Will have to have a play more, so many things to explore!


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