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Reading DOF Calculator


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#1 Jared Model

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Posted 02 June 2011 - 08:08 PM

This is a pretty newb question but want to make sure I'm reading the DOF calculator right.

35mm film
lens 18mm
t 2
distance 15 ft

it says I have 28.83 feet of DOF, (5.67 in front, 23.16 behind). so in other words if Im set to 15 feet and my subject moves back to 25 feet and then comes forward to 10 feet I won't have to pull and can just keep my lens on 15 feet since those distance are within my range of DOF and will be sharp?
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#2 Stephen Williams

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Posted 03 June 2011 - 03:50 AM

Whilst they may well be in range, you should always pull focus IMHO.

This is a pretty newb question but want to make sure I'm reading the DOF calculator right.

35mm film
lens 18mm
t 2
distance 15 ft

it says I have 28.83 feet of DOF, (5.67 in front, 23.16 behind). so in other words if Im set to 15 feet and my subject moves back to 25 feet and then comes forward to 10 feet I won't have to pull and can just keep my lens on 15 feet since those distance are within my range of DOF and will be sharp?


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#3 Marcus Joseph

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Posted 03 June 2011 - 08:19 AM

Whilst they may well be in range, you should always pull focus IMHO.

Yes, Stephen is completely right. You want to achieve an optimal level of sharpness at all times and this would essentially mean to pull focus at whatever the marks may be. I would say it's in relation to your aperture and format of choice to determine how critical focus pulling is, but on 35mm and t/2, I think focus is extremely critical and noticeable. I would treat the DOF calculator as more of a safety rather than base your focus decisions around it.

There are times when not pulling focus can be very aesthetic, Ocean's 11 and The Social Network (bank teller shot) come to mind, when there is a fantastic blur and the subject walks directly into beautiful sharpness. I would say that's a combination of good focus marks and marks for the actor.

Edited by Marcus Joseph, 03 June 2011 - 08:21 AM.

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