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Old Sep 2, 2010, 6:40 PM   #41
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Im so not getting pulled into this again!

Bottom line, shoot what works for you!
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Old Sep 2, 2010, 6:45 PM   #42
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Im so not getting pulled into this again!

Bottom line, shoot what works for you!
Got it.

This is an academic exercise.
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Old Sep 2, 2010, 8:33 PM   #43
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Still not convinced of Peripatetic's viewpoint (pun intended).
Back to the pinhole camera - DOF for practical purposes, infinite. Photo has a large square object in the foreground, and another in the background. The objects are physically the same size, but, due to perspective, the b/g object apppears smaller.
Both are in focus, but as you view the print from an increasingly greater distance, the b/g object will appear to blur more than the one in the f/g. Your apparent DOF is a completely subjective phenomenon.

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Old Sep 3, 2010, 1:57 AM   #44
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Suppose you have a photograph. (I know that's a stretch for many of you, but humor me. )
LOL. You crack me up dude.

Of course this is simply a good-natured academic exercise.

We all know how to get the results we want. If you want less DOF - get a longer lens and use a wider aperture. That can actually be condensed even further to a single rule: get a more expensive lens. :-)

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Im so not getting pulled into this again!
*struts around making chicken noises and flapping his elbows*

Right, so we need a sports photographer. Go down to a football field which has handy yardage markings on the side. Focus on the halfway line. Make a large print and hang it on the wall. As you walk backwards and forwards does the apparent DOF change?

My experience is that it does.

And the edges of a photograph don't get blurry for me as I change distance they always seem sharp and straight.

The thing about pinhole photography enters into a different realm I think where the DOF is effectively infinite, but the resolution at all distances is very poor. A big pinhole is probably f180, smaller pinholes probably around f2000 or so. Plug that into the DOF equations and your chosen CoC is basically not relevant any more.
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Old Sep 3, 2010, 7:59 AM   #45
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... If you want less DOF - get a longer lens and use a wider aperture. That can actually be condensed even further to a single rule: get a more expensive lens. :-)
Ain't that the truth!
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Old Sep 3, 2010, 8:24 AM   #46
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Got it.

This is an academic exercise.
Well then I will sit back and watch, maybe Ill learn something

I save the chicken noises for late nights with the wife.

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Old Sep 3, 2010, 9:12 AM   #47
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I save the chicken noises for late nights with the wife.
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Old Sep 3, 2010, 9:33 AM   #48
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I save the chicken noises for late nights with the wife.
Talk about a circle of confusion!! :O
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Old Sep 3, 2010, 8:44 PM   #49
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The thing about pinhole photography enters into a different realm I think where the DOF is effectively infinite, but the resolution at all distances is very poor. A big pinhole is probably f180, smaller pinholes probably around f2000 or so. Plug that into the DOF equations and your chosen CoC is basically not relevant any more.
Ah, since the example doesn't fit your preconceptions, it is invalid or irrelevant?
Ok, sharpen up the pinhole shot with a deconvolution routine - bring the Coc down to whatever you like - it is still the same for the whole shot, yet your perception of it will still be of the background as more blurred than the foreground. But of course, as they probably don't say-"Perception is nine tenths of the law."

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Old Sep 4, 2010, 8:45 AM   #50
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No, it's not my preconceptions.

With a pinhole you have an f-stop of say f500, a focal length of say 50mm.

The aperture is so small that whatever CoC you choose the DOF extends from just a few inches in front of the camera to infinity. Pinholes are an extreme version of what happens in small-sensor P&S cameras.

CoC is only 1 of 4 inputs into apparent DOF. If you push the other values to extremes, with short focal lengths and very small apertures then the image is not going to be very sensitive to CoC. But blow it up to say billboard size and stand close, and then sure you may start to see changes, but it is going to be difficult to see because the resolution is very low on pinhole cameras. Also with pinhole cameras you are often using large film, which makes CoC inherently quite large in itself.

So I don't think pinhole cameras invalidate the equations at all, they're just difficult to use to show what's going on. I'm not even sure they really apply when you don't have a lens. But for the sake of the academic exercise let's see what we can get.

But okay, let's see. 35mm film, 50mm focal length.

H= (f^2 / Nc) - f

= (50^2 / 500 * 0.03) +f

= 50.15mm

And because we don't actually have a lens that can be focussed, let's assume the focus distance is at infinity. As a proxy for infinity let's try 1km distance = 1,000,000 mm

Dn = (1,000,000 * (50.15 - 50)) / ( 50 + 1,000,000 - 2*50 )
= 150,000 / 999,950
= 0.15mm

Which is to say that everything from the pinhole to infinity is inside the apparent DOF.

Note that this assumes an f-stop of 500 and a focus distance of 1km, many pinhole cameras have even smaller apertures and 1km is acting as a proxy for infinity, so it will actually be < 0.15mm in the real world. Everything is equally in focus.
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