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07-12-2016, 08:44 AM   #1
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Aperture and Focus

Hi all,
I'm getting a decent grip on learning the basics of manual camera settings (at least I think so..)

One circumstances here boggles my mind.. Narrow depth of field coupled with infinity focus.

I understand that a large aperture provides more light, but also narrows the depth of field and blurs the background.
How does that work with a zoom lens at 'infinity focus'.
I can isolate focus of objects close to me, but the further away I focus the aperture seems to have little effect on depth of field. What exactly is happening here?

Can anyone provide some explanation or provide some sources that I can read to understand the relationship between DoF and different focusing distances, in particular infinity focus?

Thanks all!

07-12-2016, 08:54 AM   #2
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Join Date: May 2013
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Not a bad place to learn: A Flexible Depth of Field Calculator
Teach yourself by experimenting - entering different values. Also by reading the tutorial.

07-12-2016, 09:37 AM   #3
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Location: Vancouver (USA)
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I have found that the CambridgeInColor Web site has excellent tutorials on this sort of stuff.

Learn Photography Concepts

As noted in MrB1's comment above, experimentation is also helpful. You have already learned something useful; differences in DOF at infinity for various apertures are imperceptible.

07-12-2016, 02:06 PM   #4
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DOF is affected by three parameters:
1) aperture (larger aperture f/2=shallow dof)
2) focal length of lens (longer focal length=shallow dof)
3) hyperfocal distance (closer subject=shallow dof)

Even with 2 out of 3 parameters correct, you can get the opposite effect. Thus even with f/2 with a long lens, you may still get great dof if youʻre focused at infinity. And you will find that the lens focal length and distance to the subject will often have a greater affect on dof than the aperture. My favorite site that shows this relationship is


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