DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
awaldram Forum Pro • Posts: 12,949
Re: Awaldram

falconeyes wrote:

awaldram wrote

As to Falconeyes white paper I said it was unproven and thefore made up, It's his view and like most things has stuff I agree with and stuff I don't but if unproven its all conjecture.

I just see this now. Didn't know people exist who consider it a conjecture. However as I wrote in the white paper, I went through the math to proove every statement I make in the paper. So, it isn't a conjecture. And as it is easy to proove, just textbook exercise level, I never saw a point to bother readers with the math. They either understand (and are easily able to replicate) the math or they don't. Moreover, I had extensive private communications about it and its math was never challenged (equations need a minor modification if you drop the assumption of small magnification).

I really think the problem is one of language. E.g., terms "exposure", "illuminance", "luminance" and "luminous flux" are sources of confusion (I don't exclude my white paper here because I didn't anticipate this problem).

Esp. exposure should be avoided or clearly defined, e.g., if it represents an EV or a LV.

Regarding this thread, I wonder what is discussed actually. There seems to be a basic consensus. I think what remains is different use of words and assumptions about possible hidden agenda of some participants. Which is funny as the underlying facts are too simple to spend more than, say 3 posts

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Falk Lumo

Yep I'd agree with that , as I said around 2 million posts ago it looks like two side of the same coin.

Actually looking back it was Mike pointed it so I'm claiming false credit

If your attempting to normalize DoF you end up with Ian's view of the world. If you more interested in shutter speed and reach and fact then the exposure Vs Noise becomes the overriding issue.

As you say the problem is people using internationally defined measurements and then saying they alter. 150years of photography theory down the toilet in 1 sentence

On your white paper I mostly agree just think you need many more caveats around your equivalence model to make it water tight and probably need some 'proofs' either examples or algorithms to ensure people don't get confused with what it means.

You probably also want to cover off pin-hole cameras as their almost infinite DoF break the equivalent model as presented, Something along the line that no part of the image is sharp and therefore there is no DoF start point or end point (roughly).

I think it worth pointing out the DoF in itself is a misnomer there is no Depth there is only 1 plane of sharpness that is where the sensor is.

From there the image becomes progressive more OOF how quickly that happens depends on the aperture at capture time.

Now once captured how much of that blur looks sharp depends on viewing distance, viewing size and original capture size.

Or in short covering all 'magnification', the sensor size is only 1 component of that magnification and as I think I've proved can be cancelled out by altering the viewing magnification either by cropping or altering the viewed distance (looking closer).

Of cause there is one other aperture that will alter perceived acceptable sharpness this is an auto aperture that everybody uses daily it called the eye and is why light levels are critical if DoF is a crucial part of the images make up.

Which is what lead me to my opening gambit "I Don't recognize this Equivalence at all".

I have the same issue in thinking all photographs must subscribe to an equivalence look of some other format sensor, The same as I do averaging everything to 8Mp as some review site do.

A camera is a tool it may or may not do the job you want , if it does I don't think it matters whether its a box brownie or hasselblad and comparing it to something else is pointless.

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