Can someone explain the DOF rule of 1/3 front, 2/3 back to me?

timor

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You should use the DOF marking on your lens to determine where to place the focus!
Where did you see this markings lately on the lenses ?
 

480sparky

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Also, with a 28mm at f/16 put the focus anyplace you like. It doesn't matter.

Hyperfocal is 6½'. That will cover everything from 3 feet and out.
 

timor

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Deleted. Doubled.
 

ronlane

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480sparky,

If I understand what you are saying, then when I pose a group of people with the 28mm at f/16, to get the best focus of the group faces, I need to focus on the persons face that is closest to me?

Not necessarily. By focusing on the closest person, you may run the risk of the back row being out of focus. If you have people closer to 2.84' away (gawd knows why you would with a 28mm, but hey, this is all theoretical anyway) or more than 21.15', then your DOF won't get everyone in focus.

I agree about the 28mm unless it was a REALLY big group. I was just using your example. Change it to an 85mm at f4 with subject about 10-15 ft away.
 

480sparky

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I agree about the 28mm unless it was a REALLY big group. I was just using your example. Change it to an 85mm at f4 with subject about 10-15 ft away.

I don't need to refigure it because you don't want to focus on the front row.
 
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OfMikeandMen

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So, in other words, if I set my focus point and subject directly in the middle of the frame, then 2/3 of the frame behind them will be focused, and 1/3 of the space in front of them will be in focus? Thanks everyone for your input. I am not necessarily trying to employ this technique, just understand it. Thanks.

For instance: I put a 28mm on my camera, set it to f/16 and focus on a subject 5 feet away. My total DOF 18.31 feet.... 2.16' of which extends from the subject towards me, and 16.15' on the other side. Hardly 1/3 : 2/3.

Is there any solution to figuring this out without a calculator, or is it better just to get a feel of the lens you're using?
 

480sparky

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Is there any solution to figuring this out without a calculator, or is it better just to get a feel of the lens you're using?

I just end up going by experience with the lens.
 

Ysarex

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So, in other words, if I set my focus point and subject directly in the middle of the frame, then 2/3 of the frame behind them will be focused, and 1/3 of the space in front of them will be in focus? Thanks everyone for your input. I am not necessarily trying to employ this technique, just understand it. Thanks.

For instance: I put a 28mm on my camera, set it to f/16 and focus on a subject 5 feet away. My total DOF 18.31 feet.... 2.16' of which extends from the subject towards me, and 16.15' on the other side. Hardly 1/3 : 2/3.

Is there any solution to figuring this out without a calculator, or is it better just to get a feel of the lens you're using?

The calculators used to be inscribed directly on our lenses, but progress, you know -- as Sparky suggested recent progress hasn't been what some of us would call forward. Here's a review of Fuji's new 14mm lens that does still have a calculator right on the lens: Fujifilm XF 14mm F2.8 R review: Digital Photography Review This should help with the concept: DOF but apart from getting a feel for it you need a calculator. It's not a direct function of the lens you're using. The operating variables are magnification and the f/stop. The lens figures into magnification but different lenses can be used to attain the same magnification at the focus plane by having them at different distances.

At high magnifications (macro) and large apertures the DOF is very slight (measured in fractions of an inch) and the distribution is nearly even. As you decrease magnification you increase DOF and the distribution becomes increasingly uneven. As you decrease the size of the aperture you increase DOF and the distribution becomes increasingly uneven. Altering the magnification by a factor of 2 alters the DOF by a factor of 4. Altering the aperture by 1 stop alters the DOF by about 50%.

You'll get a feel for it.

Joe
 

timor

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At high magnifications (macro) and large apertures the DOF is very slight
You should also add, that with very small apertures DoF could be defeated by diffraction and focus shift rather will happen with most of the lenses. Significant with macro.
 

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