Is DoF an optical, perceptual or a hybrid property ?

Started 4 months ago | Discussions thread
guy_incognito1 Junior Member • Posts: 41
Re: Photography is about perceptual engineering

Le Artiste wrote:

Phil A Martin wrote:

Gerry Winterbourne wrote:

I don't know what you are trying to say here. The frame diagonal is irrelevant, except as a yardstick by which to quantify the amount of blur that isn't visible to the viewer.

The Yardsitck is kind of important when dealing with proportional quantities.

What affects the relative blur between different items in the scene isn't aperture, circle of confusion or most of the other factors in DOF. What affects their relative blur is their distances from the plane of focus.

See, that's just plain wrong.

Given two objects at different distances from the focus plane, stopping down while keeping everything else fixed will decrease their degree of blur relative to each other as well as relative to the frame size while stopping up will increase it. Magnifying the print otoh will increase the perceived degree of blur of both relative to the print but not to each other. Really I can't think of a way to phrase it more simply than that.

We are fighting an uphill battle here, The Artist clearly has some major misunderstandings about DoF and has clearly confused himself, yet despite all the good advice, he is point blank refusing to listen to anyone. Until he does, I'm not sure if there is much point pursuing this discussion further?

I think there are at least two people here who understand what I'm talking about, just because you're invested in not recognizing it doesn't mean it's me being confused.

Cameras are only in focus in a single 2D plane. Everything before and after is not in focus.

So to you, what does "depth of field" mean?

What do words mean in the first place?

The terms "circle of confusion" and "depth of field" have definitive definitions, which involve the acuity of human vision, and hence viewing distance.

You want to redefine "depth of field" into something meaningless, away from the accepted definition. Go invent your own term that has limited practical use and try to get other people to talk about it.

Edit, to expound:

The accepted definition of depth of field is: the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image.

The definition of "acceptably sharp" is based on human visual acuity, which depends on distance.

You want to redefine "depth of field" to mean something akin to: the relative change in the size of the circle of confusion at the focusing plane compared to things at distances before and after the image.

But that definition is basically not very useful and doesn't even use the word "depth".

Like, no one really cares? it's meaningless to humans who look at images.

Maybe if you were using the pictures to do some other purpose other than for human visual enjoyment, it would matter.

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