A poll about depth of field

Started 2 months ago | Polls thread
Tom Axford Veteran Member • Posts: 8,259
Re: A poll about depth of field

Quarkcharmed wrote:

Tom Axford wrote:

Pixel Pooper wrote:

No, the DOF is not infinite. If it were, the chimney would not be outside of the DOF.

If you focused at the hyperfocal distance you would get more DOF, and you can't have more than infinite.

You can have more than infinity:

infinity + x = infinity

is one of the basic properties of infinity, just as:

zero + x = x

is one of the basic properties of zero.

The distance from any point to infinity is infinite, it doesn't matter where that point is. If the only things in sharp focus are the stars, then the DoF is at least the distance from one of those stars to infinity, which is an infinite distance (whichever star you choose).

It's not quite like that.

Why do you claim to disagree with me?

Nothing you have said in the rest of your post contradicts what I said.  It simply elaborates on some points that I did not.

Because you can see all stars in focus (sharp enough), DoF must be greater than the distance between any two stars, or between a closest star to farthest one. That means DoF has to be practically unlimited. That's why DoF is 'infinite' - because we can't find the limit. That's the conclusion before we use any actual calculations.

Now let's calculate it. In theory the far limit of DoF goes to infinity when focus distance approaches the hyperfocal distance which follows from the conventional formula for near and far limits of DoF. Because the distance to the stars is way greater than any hyperfocal distance, the far limit of DoF is at infinity when we focus on a star.

However if you actually try and focus closer, at hyperfocal distance, which is way closer than stars, you'll get an ok result for landscape but the stars will be blurred, so the formula above is an approximation.

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