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DOF questions

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Billx08 said:
Kim Letkeman said:
Rachotilko said:
OK, I'll relax a bit now.

Anyway, it was Pdude (the OP) who wanted to know the reasons for limited DR of small sensor cameras. And I honestly believe those reasons have nothing to do with tonal curves, or blown highlights - those are actually symptoms, not causes of limited DR. So I wanted to provide him the clarification.
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Well, using said logic, SNR is also just a symptom. What is the actual root cause?
  1. Small full welll capacity because of tiny photosites, which is something that Bill already mentioned IIRC.
  2. Low total light gathered because of small sensor. Another cause of overall image SNR issues.
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Precisely, and I actually referred to both of those points in the same sentence in my reply to painterdude :
Billx08 said:
It's the related problems of not capturing enough photons, both by the photosites and by the entire sensor.
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But they're the type of nits that some nitpickers willfully go out of their way to ignore. :)
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They are not 'ignored' - they simply don't require any comment or correction.

The problem with your messages is not what you get right - it's what you get wrong, which is unfortunately frequent and numerous.

I.e., no less than 6 examples, in this thread alone...
  • 1) Claiming that 18.6m "clearly isn't anywhere near infinity" - which on the 17mm FF lens in question, it actually is.
  • 2) Suggesting 'diffraction' affects/limits DoF - which it doesn't.
  • 3) Stating "the tone curve... determines dynamic range" - which it doesn't.
  • 4) Claiming "4 photons could have a 10 stop dynamic range" - which is nonsense.
  • 5) Associating 'posterisation' with 'solarisation' - which are two completely different things.
  • 6) Stating that "wide apertures..." , required for minimum diffraction, would require "...the shutter speed slow enough and use a tripod" - which is quite a 'brain-fart'.
...these are not 'nits' - they are errors, mistakes, and misinformation.

Making 'mistakes', in itself, is really not a problem - but, being unable to deal with them without throwing a childish tantrum, shouting "stalker... vendetta...etc" , and posting cartoons and 'youtube' clips - that really is.
 
Mark H said:
Mark H said:
But they're the type of nits that some nitpickers willfully go out of their way to ignore. :)
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They are not 'ignored' - they simply don't require any comment or correction.

The problem with your messages is not what you get right - it's what you get wrong, which is unfortunately frequent and numerous.

I.e., no less than 6 examples, in this thread alone...
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No, they're not wrong. It's just that you're going out of your way to misunderstand and misinterpret, taking what I've written far out of context. For example, solarization is a technique, not the same as posterization, but it produces a similar contour map effect that solarization devotees would recognize, which is why I wrote :
Mark H said:
It's the related problems of not capturing enough photons, both by the photosites and by the entire sensor. Imagine an extremely small photosite, only large enough to capture 4 photons at most. Not much of a dynamic range there. Compare that with some photosites that can record the accumulation of more than 50,000 photons. It's more complicated than this, because the tone curve applied to the sensor data by the camera determines the dynamic range, and theoretically, that sensor whose photosites can only capture 4 photons could have a 10 stop dynamic range, but it would be a thoroughly useless dynamic range because it would be able to display such a tiny number of different tones. This would be great for posterization lovers, but it would be pretty useless for general photography unless you're into solarization.
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This shouldn't be too hard to understand, for most people that aren't driven by irrational obsessions. Pretending that I conflated posterization with solarization, in other words that they mean the same thing shows a sad dishonesty, the kind that you succumb to over and over and over. Get over it.

Time (and your vendetta) marches on, and for a change of pace . . .



 
Billx08 said:
Mark H said:
Billx08 said:
But they're the type of nits that some nitpickers willfully go out of their way to ignore. :)
Click to expand...
They are not 'ignored' - they simply don't require any comment or correction.

The problem with your messages is not what you get right - it's what you get wrong, which is unfortunately frequent and numerous.

I.e., no less than 6 examples, in this thread alone...
  • 1) Claiming that 18.6m "clearly isn't anywhere near infinity" - which on the 17mm FF lens in question, it actually is.
  • 2) Suggesting 'diffraction' affects/limits DoF - which it doesn't.
  • 3) Stating "the tone curve... determines dynamic range" - which it doesn't.
  • 4) Claiming "4 photons could have a 10 stop dynamic range" - which is nonsense.
  • 5) Associating 'posterisation' with 'solarisation' - which are two completely different things.
  • 6) Stating that "wide apertures..." , required for minimum diffraction, would require "...the shutter speed slow enough and use a tripod" - which is quite a 'brain-fart'.
...these are not 'nits' - they are errors, mistakes, and misinformation.
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No, they're not wrong.
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LOL - they are, and very plainly too - and deleting them from your response will neither help, or alter that.
Billx08 said:
It's just that you're going out of your way to misunderstand and misinterpret, taking what I've written far out of context.
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Not remotely.

You'd have to go "far out of context" to even begin to make any sense of some of these things that you have written.
Billx08 said:
For example, solarization is a technique, not the same as posterization, but it produces a similar contour map effect that solarization devotees would recognize,...
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'Solarisation' is a technique that produces a reversal of tones - whereas 'posterisation' is an effect of limited number of tones.

They are quite two quite different techniques, with quite different results.

The key point here is that 'solarisation' has absolutely no connection whatsoever to the subject of sensor dynamic range, numbers of photons, etc.
Billx08 said:
which is why I wrote :
Billx08 said:
Billx08 said:
It's the related problems of not capturing enough photons, both by the photosites and by the entire sensor. Imagine an extremely small photosite, only large enough to capture 4 photons at most. Not much of a dynamic range there. Compare that with some photosites that can record the accumulation of more than 50,000 photons. It's more complicated than this, because the tone curve applied to the sensor data by the camera determines the dynamic range , and theoretically, that sensor whose photosites can only capture 4 photons could have a 10 stop dynamic range , but it would be a thoroughly useless dynamic range because it would be able to display such a tiny number of different tones. This would be great for posterization lovers , but it would be pretty useless for general photography unless you're into solarization .
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Click to expand...
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Indeed, quite - one paragraph which contained no less than 3 different errors/pieces of misinformation/incorrect associations.
Billx08 said:
This shouldn't be too hard to understand, for most people that aren't driven by irrational obsessions. Pretending that I conflated posterization with solarization, in other words that they mean the same thing shows a sad dishonesty, the kind that you succumb to over and over and over. Get over it.
Click to expand...
The "dishonesty" is entirely on your part 'Billx08' - "conflate" (your choice of wording) the two terms, the two techniques, is almost exactly what what you did do; you put them together - so "get over it" yourself.
Billx08 said:
Billx08 said:
Making 'mistakes', in itself, is really not a problem - but, being unable to deal with them without throwing a childish tantrum, shouting "stalker... vendetta...etc" , and posting cartoons and 'youtube' clips - that really is.
Click to expand...
Time ( and your vendetta ) marches on, and for a change of pace . . .

http://spiritualnetworks.com/file/attachment/2012/02/113e08351d725f84d58c1c17f4f6b7ce_view.jpg
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There is no "vendetta" on my part - but your self-denial, and continuing childish reaction, that is what... "marches on" .
 
Lloydy said:
... May not answer all your questions, but will give you some good understanding :

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

Great site for reference material.

--
Dave
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Not bad they got the distribution of the DOF right (due to focal length changes)

Linking to the luminous Landscape a bad idea..they failed to mention that

There is some mis information on your link above which tries to suggest focal length "is not part of the DOF it's magnification" this is wrong. Focal length is part of the formula for DOF (it is cast in stone)

BUT

What they all fail to mention is the obvious one. It is a variable..so is distance to subject the 2 can wipe each other out as such. But the fact remains that any attempts to suggest focal length and DOF are not related is "PURE HOGWASH" or epic proportions. And I blame the LL for that among other sites with confusion on this issue.

It is also incorrect to state that in all cases keeping the same subject distance (a better word is focus distance) and with variable focal lengths

http://www.dofmaster.com/dof_imagesize.html

It does not apply in all cases

Thus your link and the LL are wrong.
In a way that simply adds to confusion on the subject

To the OP the focal length of the lens on these small sensors is very small, thus the DOF is much larger. It really is that simple

Too many sites tried to discount focal length when it's a critical part of the formula (but a variable one)

If I were Cambridge in colour I would go back and try to explain things better, if I were the luminous landscape I would just give up!
 
I have no idea what the local time was when you wrote that rebuttal, but it rambles, sentences are incomplete, and you are simply wrong.

The article at Cambridge is accurate. It notes the same focus shift at shorter focal lengths (more rear DOF versus longer focal lengths) as the link you included. It shows the effects of aperture very clearly. What it misses is a similar example showing the effects of focal length and subject distance, but he does that with several tables. He then references an article where he covers crop factor as it pertains to field of view etc.

Both articles together are very clear as to the relationship of focal length, focus distance and sensor size.

I'm not sure why you are in hyper critical mode these days, but you missed the target completely here from what I can see.

--
http://kimletkeman.blogspot.com
 
Kim Letkeman said:
I have no idea what the local time was when you wrote that rebuttal, but it rambles, sentences are incomplete, and you are simply wrong.

The article at Cambridge is accurate. It notes the same focus shift at shorter focal lengths (more rear DOF versus longer focal lengths) as the link you included. It shows the effects of aperture very clearly. What it misses is a similar example showing the effects of focal length and subject distance, but he does that with several tables. He then references an article where he covers crop factor as it pertains to field of view etc.

Both articles together are very clear as to the relationship of focal length, focus distance and sensor size.

I'm not sure why you are in hyper critical mode these days, but you missed the target completely here from what I can see.

--
http://kimletkeman.blogspot.com
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Kim you usual rambling post filled with misinformation as expected.

I simply call out the 2 sites as incorrect (as they are) and anyone dumb enough to suggest that the focal length is not part of the formula for DOF is treading on nothing..they've already fallen through the ice.

This is cast iron..set in stone not up for debate.

And I've make a link which clearly shows that the so called claims of "same DOF" at numerous focal lengths is just what it is..pure tosh. It's a basic concept not properly explained.

The only good point was it did (unlike the LL article) explain that the DOF distribution is not the same at various focal lenghts. And the DOF is not identical either

Kim I'd suggest a good read of a book, because clearly you have a very crude and basic understanding of DOF.

I called the Luminous Landscape out on this..and continue to do so, their DOF articles are poor and do not inform readers of the real story with DOF
 
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