# A poll about depth of field

Started 2 months ago | Polls thread
Re: Depth of Field is not a precise mathematical concept
1

tbcass wrote:

Quarkcharmed wrote:

All of the above doesn't matter. Whatever input parameters you choose, including CoC, when focus goes to infinity, DoF goes to infinity. The blurred chimney and out of focus foreground don't change that,

That's not the way DOF is defined.

It is the way DoF is defined in all the reputable sources that I am aware of.  In fact, you yourself have several times said that DoF is the distance between the near limit of what's acceptably sharp and the far limit.

However, even if you want to define DoF as meaning the pair of distances (near limit, far limit), one can still talk about the length of the DoF, meaning the difference between those two values.

It's not how far out something is in focus. Let's use an example If I have a camera setting that gives me a DOF from 10 feet to 100 feet where everything between 10 ft and 100 ft is in focus the DOF is not 100 feet. It is 10 feet to 100 feet. If the focus is set to infinity but everything closer than 50 feet is blurry then the depth of field is 50 ft to infinity. DOF is always expressed as a range, not a single number.

OK, if the near limit is 10ft and the far limit is 100ft, the distance between those is 90ft and I would say that the DoF is 90ft.

Suppose we focus a bit further away and the near limit is 50ft and the far limit is infinity. The difference between those two is infinity.  I would then say that the DoF is infinity. All of the DoF calculators that I have used would also say that the DoF is infinity.  All of the books I have read on depth of field would say the same.

DoF still goes to infinity.

See that's where you are going wrong. You are thinking "goes to" infinity. Just like my example where the DOF "goes to" 100 feet. It's not where it goes to. It's the range between. In the original example, the range is somewhere beyond the chimney to infinity.

If the far limit goes to infinity, then the distance between near and far limits also goes to infinity and that is the conventional definition of DoF.

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