jwbryson1
TPF Noob!
- Joined
- Apr 21, 2011
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- 4,280
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I have been reading a lot about these lately and feel like I have a pretty good grasp on them, so I am either having an "off day" or I need to keep thinking about how they relate to one another.
With my cell phone app, I have calculated a sample DOF and HFD based on the following parameters: f/11, subject distance 75 feet, focal length 90mm. The app tells me the DOF near limit is 46.3 feet, and the DOF far limit is 196.6 feet, for a total DOF of 150.2 feet. It also tells me that the DOF starts at 28.7 feet in front of the subject (or 46.3 feet from me) and the DOF ends at 121.6 feet beyond the subject.
It also tells me that my HFD is 121.1 feet. So, based on an HFD of 121.1, my DOF should extend from 1/2 of the HFD to infinity, or from 60.55 feet (121.1 / 2) to infinity. :scratch:
So my question is as follows: If the DOF based on HFD starts at 1/2 of the HFD, or here at 60.55 feet, why does the DOF calculation say that the DOF starts at 46.3 feet in front of me instead of at 60.55 feet?
EDIT: To add to this discussion, if the portion of the photo that is in focus is within the proper DOF, in my example above would an object 51 feet in front of me be in focus or would it need to be more than 60.55 feet from me?
[Sits quietly and waits for KmH to come knock him around a bit...:mrgreen:]
With my cell phone app, I have calculated a sample DOF and HFD based on the following parameters: f/11, subject distance 75 feet, focal length 90mm. The app tells me the DOF near limit is 46.3 feet, and the DOF far limit is 196.6 feet, for a total DOF of 150.2 feet. It also tells me that the DOF starts at 28.7 feet in front of the subject (or 46.3 feet from me) and the DOF ends at 121.6 feet beyond the subject.
It also tells me that my HFD is 121.1 feet. So, based on an HFD of 121.1, my DOF should extend from 1/2 of the HFD to infinity, or from 60.55 feet (121.1 / 2) to infinity. :scratch:
So my question is as follows: If the DOF based on HFD starts at 1/2 of the HFD, or here at 60.55 feet, why does the DOF calculation say that the DOF starts at 46.3 feet in front of me instead of at 60.55 feet?
EDIT: To add to this discussion, if the portion of the photo that is in focus is within the proper DOF, in my example above would an object 51 feet in front of me be in focus or would it need to be more than 60.55 feet from me?
[Sits quietly and waits for KmH to come knock him around a bit...:mrgreen:]
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