Which Influences Depth of Field more: aperture or distance from subject?

I've been wondering about this for awhile now, and haven't yet found a clear answer.

It's generally understood that aperture and distance from the subject (and, to a lesser extent, focal length) factor into an image's depth of field.

But with all other things being equal, which contributes more to depth of field? Which would have shallower depth:

50mm lens DSLR (APS-C) @ 1.4F from 8 meters from subject
OR
50mm lens DSLR (APS-C) @ 2F from 6 meters from subject?
OR
50mm lens DSLR (APS-C) @ 8F from 2 meters from subject?

And why?



(this is my first post, so my apologies in advance if this in the wrong forum or a bit of noob question.)

Hi there,

Welcome to the CiC forums from me, and don't worry, this forum is just the right place for this question.

First question (for you), have you read the Understanding Depth of Field tutorial here?

To answer your three examples, I went to the end of the page linked above, and put the values into the Depth of Field Calculator (it's about 3/4 down the page)

Non variables; 50mm and APS-C - I'll assume 1.6 for Canon, although the difference for 1.5 cf Nikon will be minimal and won't affect the comparison aspect of the question.

Variables (and answers):
Aperture f1.4, subject 8m = 1.436 m
Aperture f2.0, subject 6m = 1.153 m
Aperture f8.0, subject 2m = 0.507 m

Conclusion:
As you can see; a closer camera to subject distance has a huge effect at reducing DoF, even if you increase the aperture number by 4 stops.

Does that help?

Second question for you; do you have a first name we can use please?

Cheers,

Here's very detailed depth of field calculator - answer to all your questions!

http://www.dofmaster.com/dofjs.html

Thanks guys!

Dave --

Feel free to call me Richard :)

I read the DoF tutorial here a while ago, and found it very useful. Indeed, using that knowledge I've been experimenting w/ DoF quite a bit, and it was while shooting that I started to wonder if there was a formal relationship b/w aperture and distance. It slipped my mind, though, before I posted this thread that there was a DoF calculator right in that tutorial (doh!)

Thanks for posting those numbers and helping me reach a sound conclusion though. Now all I need is a way to take this calculator with me when I shoot so I can decide whether I should stop down or move closer!

Hi Richard,

Quote:

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Originally Posted by shochiku

Now all I need is a way to take this calculator with me when I shoot so I can decide whether I should stop down or move closer!

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If you have an iPhone, as the saying goes; "there's an app for that".
I don't have one :( so I'll let someone that does provide the link ;)
I wonder if there is one for a Blackberry?

Quote:

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Originally Posted by shochiku

Thanks for posting those numbers and helping me reach a sound conclusion though.

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No worries; you might be surprised how often answering a question benefits us too :)

Cheers,

Quote:

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Originally Posted by Dave Humphries

I wonder if there is one for a Blackberry?

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This is the best link I could find for Blackberry users :p