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12-22-2009, 06:42 PM   #166
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QuoteOriginally posted by Ben_Edict Quote
Marc, if you find that concept helpful, than it is fine for you.
And for anyone else interested in comparing the performance of different camera/lens systems.

QuoteQuote:
But how you can now even mix "noise" into that equivalence is a complete mystery to me.
I don't see why that should be the case, because I've explained it many times.

QuoteQuote:
* Noise is a sensor property (unless you're talking about noise on the level where the law of uncertainty starts to be important).
Noise is a property of the sensor *and the amount of light that falls on it*. That's where the equivalence comes into play - it gives us a way of equalizing that factor.

QuoteQuote:
So, if we mix up those very different technical or physiological aspects, it may by mere coincidence work for you now. But it won't work tomorrow, when other sensors with other noise behaviour will be available or not even today, for most other people, because you would need to redefine your equivalence for every possible comparisson pairing of FF and APS-C format cameras (not to talk about MF etc.)
No, as I've explained multiple times, I'm talking about comparing sensors of the same technology. In other words, we're talking about the difference due to the *size* of the sensor, as opposed to the technology employed. Yes, there may be technology differences. They are extremely unlikely to trump the size differences, though. The idea here is to compare performance on APS-C *in general* with performance on FF *in general*, not to compare any two particular cameras. And despite what you seem to be implying, this is in fact a quite reasonable thing to want to do. If one is considering a move to FF, one wouldn't normally do so because of just one camera's performance.

12-22-2009, 06:50 PM   #167
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QuoteQuote:
You could have cut right to a particular sentence or section of my post you took issue with and reply to that. As opposed to blowing off an entire post by saying "lots of text deleted", and then responding in a way that made it clear you didn't understand anything I wrote.
I didn't "blow off" your text, I made a post that responded to all of it, removing the need to quote the entire post, in efforts to make my post more readable. Here, let me get into hysterical mode: geez, I can't even try to do something good to keep posts clean without you equivalence guys getting on my case?!? I bet if I saved a cat from a burning building, you'd have me arrested for tresspassing!

That's the kind of utter nonsense that is being perpetrated in this thread... you feel like you're on some kind of holy crusade, spreading the word of equivalence. When it's not like we don't believe you, it's just that we don't care about it, because it doesn't have a real-world importance...

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Again, you appear to not bothered to read or understand what I've written. Yes, those two yield the same shutter speed - but different images in every other possible way. Different fields of view, different levels of noise, different DOF. There will be *nothing* in common about the two images except the effect of the shutter speed. What on earth would the point of such a comparison be? *This* is a comparison with no real world relevance.
So you care about more than just ISO and shutter speed... yeah? Then you should write that, instead of... writing the opposite

QuoteQuote:
Except the one I've patiently explained several times now - trying to understand what benefit buying a FF camera would have to me in terms of noise when shooting low light, and what lenses I'd need to realize that benefit. I can't think of a way to make that any clearer. This is a *very real" application.
Considering that there's nothing special about the focal lengths you have now and that Pentax doesn't make a FF DSLR, no, that's not a *real* application in any way.

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Precisely. And that's why equivalence has real world relevance - because it tells you useful things about thing lots of people actually want.
I guess you didn't understand that point... that's okay lol.

QuoteQuote:
I have - several times now. The desire for lower noise levels in low light shooting is a real-world situation. Understanding equivalence is a key to learning how to *get* those lower noise levels.
No, learning how to press the left directional key on the ISO adjustment menu is the key to getting lower noise levels. Everything you're stating is a sad corruption of factuality.
12-22-2009, 06:57 PM   #168
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And rparmar *still* has not been able to continue his discussion with me (about him intentionally misquoting me -- he gave up after I pointed that out. I suppose he was hoping I endorsed his misquotation, so I would get caught up in my own words later?). I am ready to respond to any "points" he makes. But he insists on using troll tactics to debase the entire argument itself like a child throwing a tantrum, instead of respond to the things I've pointed out. And then he wonders why I said I've won?

But he still won't reply even to this message, about the points I've made. He'll just use another post to insult, miscarry, distract, or otherwise add nothing to the actual conversation at hand. It's his behaviour that makes me feel like you guys will continue treating this more like a religious issue instead of a scientific one, and we all know that there is no point in arguing about such things as that...
12-22-2009, 06:57 PM   #169
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QuoteOriginally posted by Ben_Edict Quote
he needs 40 pages to say that and in the course of that destroys any clarity. Especially the Introduction and the following Q&A section go to great length to make simple things hard to understand.
I agree, it's an overly complex writeup of a fairly simple phenomenon.

QuoteQuote:
I cannot deny, he also writes some things, which are perfectly correct and true. Among them, what I tried to get through here for several postings: that the same numerical aperture (say f/2) leads to the same expsoure on any sensor or film format (given the ISO is the same, ofcourse).
And obviously, no one has denied this.

QuoteQuote:
This simple, basic truth, will be compromised, if we are introducing "equivalent apertures", as in some of the postings in this threads, because, the uninformed reader will automatically equal that much smaller "equicvalent aperture" with an accodingly smaller "light throughput".
I guess I have no control over what uninformed people will do. This thread has proven that. Equivalence works for those who understand how to use it, and I'm here to help with that understanding.

QuoteQuote:
The term of "equivalent apertures" does only one thing: it creates confusion, because it tackles only one photographic issue (DOIF), but compromises the clarity of another issue, namely exposure.
It doesn't compromise that clarity one bit. Indeed, it requires you to already know about how exposure works, so you can understand that for a given aperture, the "equivalent" aperture on FF will require a higher ISO in order to yield the same shutter speed. That is the whole idea in a nutshell right there. Understanding the basic truth about exposure you set forth above is a prerequisite to understanding equivalence. If you have a solid foundation in that prerequisite understanding of exposure, adding the concept of equivalence on top of that is not going to shake that foundation - it is merely going to build on it.

And again, if it were truly only about DOF, it wouldn't be very interesting to many people. It's the fact that it does also perfectly characterize the noise potential that makes it remarkable.

BTW, if you're having trouble accepting that noise isn't just a matter of the sensor technology, we can actually borrow from the recent digression into audio. "Noise" in photographic terms is actually about signal to noise ratio. What equivalence does is normalize the signal level.

12-22-2009, 07:07 PM   #170
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QuoteOriginally posted by wallyb Quote
I didn't "blow off" your text, I made a post that responded to all of it
If you think that a post that concentrated on DOF - with barely a mention of noise or shutter speed - and talked about shooting at f/7.1 and f/8 had *anything* to do with what I wrote, you didn't understand what I wrote.

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When it's not like we don't believe you, it's just that we don't care about it, because it doesn't have a real-world importance...
It does; you have just not managed to understand it yet.

QuoteQuote:
Considering that there's nothing special about the focal lengths you have now and that Pentax doesn't make a FF DSLR, no, that's not a *real* application in any way.
Sure it is. The focal lengths ranges I have now are the ones my real world photographic experience tells me are most useful to me on APS-C. They are the ones my real world photographic experience tells me I'd want to find equivalents of if I were to switch to FF. And while Pentax doesn't currently make an FF camera, others do, so an understanding of this is a factor in deciding if I should switch brands to get FF. It is also a factor in deciding whether I should limit my Pentax lens purchases to ones that would be FF-compatible. It's a factor in deciding whether/when to upgrade my current APS-C to another APS-C camera or hold out in the hopes of an eventual FF one. These are real world decisions.

QuoteQuote:
No, learning how to press the left directional key on the ISO adjustment menu is the key to getting lower noise levels.
Proving once again you haven't understood anything about equivalence. Lowering ISO lowers noise - but at the expensse of a slower shutter speed. The question is, how do you lower noise *without* going to a slower shutter speed. One answer is to try to buy a larger maximum lens at your current focal length. Another is to buy a camera with a larger sensor, and a lens to give an equivalent field of view, and an aperture that will allow you to take advantage of the better noise potential of that larger sensor. How do you decide between those options? Which provides a larger improvement? What price does either solution force you to pay in DOF, size, weight, or dollars? Those are questions one can only *guess* at without an understanding of equivalence. If you're lucky, you might guess right. But I don't have to guess. I know.
12-22-2009, 07:23 PM   #171
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QuoteQuote:
Lowering ISO lowers noise - but at the expensse of a slower shutter speed. The question is, how do you lower noise *without* going to a slower shutter speed. One answer is to try to buy a larger maximum lens at your current focal length. Another is to buy a camera with a larger sensor, and a lens to give an equivalent field of view, and an aperture that will allow you to take advantage of the better noise potential of that larger sensor. How do you decide between those options? Which provides a larger improvement? What price does either solution force you to pay in DOF, size, weight, or dollars? Those are questions one can only *guess* at without an understanding of equivalence. If you're lucky, you might guess right. But I don't have to guess. I know.
Right Marc, that's all true. As I'll state for another time, I have no disagreement whether the maths are true or not. You keep saying "...without and understanding of equivalence". Frankly, it's not a hard concept to grasp...

The part that you're not getting is that you're still not stating any real-world examples of why it matters right now. I don't consider owning, for example, a Canon XTi with a 20mm f/2.8, 50mm f/1.4, and 100mm f/2, and a Canon 5D with a 30mm that you only use at f/4.2 and above, a 75mm that you only use at f/2.1 and above, and a 150mm that you only use at f/3 and above, any kind of real-world scenario in any way.

You're never going to be photographing the same exact scene ever again, so what's the point of caring so much about making the next visit the exact same? The only thing you should have to care about is the change in FOV between different-sized formats, because compensating for that will lead to a change is perspective, which has a serious effect on the resulting image.

And you don't realize that each time you change what you, personally, care about in equivalence, be it an equivalent DOF or equivalent ISO speed, that all the other parts change. So it doesn't matter... if you want to get the equivalent DOF between two lenses in two different formats, you will NOT be able to get the same ISO+shutter+focallength. If you care about having the equivalent ISO between two formats, you will not have the same DOF+shutter+focallength. If you care about the same focal length between formats, you won't have the same ISO+shutter+DOF. It's simply mathematically impossible. And until you understand this point I'm making, you'll continue saying the same things. There's still no point to trying to make-equivalent all the things you've talked about, because all the other things change... there is no "unified theory" of equivalence, and you're changing your qualifiers each time to make it look like there is.

But there's still no need to care about any other equivalent number than focal length. Caring about equivalent aperture, shutter speed, ISO, etc is all just the mathematical wankitude I mentioned earlier. Because a photo being good or not does not lie in the balance of whether 1/100s or 1/120s was the shutter speed, or whether ISO 400 was used instead of ISO 800, or anything else like that. And this point I'm making has a bigger scope than the one you continue to make (that I don't understand equivalence and what you write -- I understand it, I just find it useless and still haven't been shown otherwise), so I don't believe you'll be able to grasp it until you cool down and look at the entire discussion again.

Last edited by wallyb; 12-22-2009 at 07:29 PM.
12-22-2009, 08:30 PM   #172
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QuoteOriginally posted by wallyb Quote
Right Marc, that's all true. As I'll state for another time, I have no disagreement whether the maths are true or not. You keep saying "...without and understanding of equivalence". Frankly, it's not a hard concept to grasp...
I agree, which is why I find it strange that you can't figure out any of the many practical applications even after I've spelled them out. But that fact, combined with the fact that your rebuttals *completely* miss the point, are what suggest to me that despite your claims, you still *don't* really understand what equivalence is about. If you did understand, you would realize your arguments in no way discredit the notion of equivalence at all, since they rely on irrelevant concerns. Actually, your arguments nicely demonstrate the value of equivalence, since it cuts through the confusion of all the different variables and gets to the heart of the ones that matter and how they relate.

QuoteQuote:
The part that you're not getting is that you're still not stating any real-world examples of why it matters right now
I gave you several in my last post. I'm not going to repeat them. I'm going on vacation tomorrow and don't expect to be continuing to participate in this discussion much if at all. Feel free to claim you do understand but that your understanding hasn't led you to see any practical value. That's fine. The rest of us that understand and *can* see practical value will continue to benefit from it.

QuoteQuote:
You're never going to be photographing the same exact scene ever again, so what's the point of caring so much about making the next visit the exact same?
Might not be the *exact* same scene, but if I visit the same jazz club night after night and the same lights are on that stage each time, should I be surprised if find I get pretty much the same exposures each time? And that eventually, I might start to wonder about the limits I constantly run up against?

QuoteQuote:
And you don't realize that each time you change what you, personally, care about in equivalence, be it an equivalent DOF or equivalent ISO speed, that all the other parts change.
This is the kind of statement that causes me to say you still don't understand. The whole idea is that, no the other parts *don't* change - at least, not the parts that are actually relevant: FOV, shutter speed, noise, and DOF.

QuoteQuote:
if you want to get the equivalent DOF between two lenses in two different formats, you will NOT be able to get the same ISO+shutter+focallength
Exactly. That's because ISO and focal length are *not* among of the components of the equivalence - *noise* and "field of view" are. What are ISO and focal length but numbers to me? I don't care about *numbers*; I care about noise and field of view -thing I can see in the real world photographs I take.

So I don't care if I can't get the combination you list above, because it's not the combination I am interested in. I *can* get the same DOF, noise, shutter, and FOV, by simply using the focal lengths and apertures suggested by equivalence. And equivalence furthermore tells me how to to get an *improvement* in one or more of those areas, and what price I'll pay in terms of the other areas. That's what makes it of practical value.

QuoteQuote:
And until you understand this point I'm making, you'll continue saying the same things.
I *do* understand the point you are making - I understand it is irrelevant because equivalence is not about getting the same ISO or focal length. I keep saying the same things because they are true and somehow you still don't seem to accept them.

QuoteQuote:
But there's still no need to care about any other equivalent number than focal length. Caring about equivalent aperture, shutter speed, ISO, etc is all just the mathematical wankitude I mentioned earlier. Because a photo being good or not does not lie in the balance of whether 1/100s or 1/120s was the shutter speed
In your world, it might not. And indeed, if we're only talking about quarter stop differences, it doesn't in mine either. I could similarly say success doesn't depend on whether your focal length is 85mm or 90mm. What's the point of confusing the issue by giving examples of differences that are much smaller than the *real* differences involved?

We're talking about *full stop* differences in both shutter speed and noise - differences *just* as significant as the difference in field of view due to the crop factor. And in my world, all of that *does* matter. It is not "wankitude". Nor is trying to figure one's options in *achieving* that one stop improvement.

Last edited by Marc Sabatella; 12-22-2009 at 10:01 PM.
12-22-2009, 08:32 PM   #173
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I think a couple people here just need to get a room and get over with the foreplay...yeesh! hehehe...

12-22-2009, 08:38 PM   #174
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QuoteQuote:
Exactly. That's because ISO and focal length ae *not* among of the components of the equivalence - *noise* and "field of view" are. What are ISO and focal length but numbers to me? I don't care about *numbers*; I care about noise and field of view -thing I can see in the real world photographs I take.
So I don't care if I can't get the combination you list above, because it's not the combination I am interested in. I *can* get the same DOF, noise, shutter, and FOV, by simply using the focal lengths and apertures suggested by equivalence. And equivalence furthermore tells me how to to get an *improvement* in one or more of those areas, and what price I'll pay in terms of the other areas. That's what makes it of practical value.
FOV is a manifestation of focal length, and 'noise' is a manifestation of ISO for a given sensor (I guess you don't know that the amount of noise for a given ISO speed will be wildly different and incalculable between formats, which is the whole point of equivalence (going between formats)). You are trying to mangle words to again make it seem like I don't understand what you're saying. There's no difference between saying focal length and FOV, and noise and ISO (or shutter speed and, oh I don't know maybe "exposure time", I'm surprised you didn't say that too), and if you think there is, feel free to replace all instances of when I used them with one another.

That is a pretty low tactic in an argument to use, and if you didn't do it on purpose I'd like clarification of that. Otherwise, you're just doing the same things rparmar is doing, and there's no point in continuing with you either. Please let me know -- I'm not going to bother replying to anything else until this is addressed, there would be no point because further transgressions would go without being pointed out.
12-22-2009, 09:42 PM   #175
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QuoteOriginally posted by Igilligan Quote
"Cloud reality" is exactly what I want my DOF to do... The cloudier the better!!!!
Priceless.


QuoteOriginally posted by Wheatfield Quote
...your theory pretty much falls on it's face in a puddle of drool.
It is not "my theory" like "1+1=2" isn't my theory either. Marc and I just tried to convey some simple ways to compare different formats with each other. None of this is contentious.

QuoteOriginally posted by Wheatfield Quote
I know that if I had done a similar picture with my cropped frame Pentax it would have been a noisy mess.
You are probably right but your "real world" test does not leave "everything else equal". You are comparing different sensor technologies, A/D converters, image processing, etc. You cannot infer anything from your observation regarding crop vs FF.

I think it is time to pull out of this thread. The SNR is approaching zero with the speed of light (I'm not referring to your posts, Wheatfield). Also, I don't want to destroy the beauty of this thread that Gus described so well. One has to know when a masterpiece is finished. Hard to believe it all just started with an alliteration...
12-22-2009, 09:54 PM   #176
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QuoteOriginally posted by wallyb Quote
FOV is a manifestation of focal length
And sensor size, which is one of the relationships that equivalence is designed to capture.

QuoteQuote:
'noise' is a manifestation of ISO for a given sensor (I guess you don't know that the amount of noise for a given ISO speed will be wildly different and incalculable between formats, which is the whole point of equivalence (going between formats)).
I know noise for a given ISO will vary between sensors. What I also know - and have related many times already on this thread - is that *part* of this variation is due to technology differences that we have no control, but *part* is attributable directly and precisely calculatable to sensor size. That's the part equivalence is dealing with.

QuoteQuote:
There's no difference between saying focal length and FOV
There is a large difference when comparing across sensor formats, which you were doing. This, once again, is one of the things that equivalence is designed to make clear. This is, of course, the part everyone already knows - it's the "crop factor". But it's only part of the equation.

QuoteQuote:
and noise and ISO
Ditto, except that this is the part most *don't* realize, and have trouble accepting. ISO and noise are related by sensor size in *exactly* the same way that focal length and FOV are.

QuoteQuote:
That is a pretty low tactic in an argument to use
I have no idea what you mean by "that" in this context. The paragraph you quoted from me was a simple statement of facts.

Last edited by Marc Sabatella; 12-22-2009 at 10:03 PM.
12-22-2009, 10:00 PM   #177
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So you're purposefully not trying to understand what I wrote, Marc? Okay, I'll do the simple thing, and restate what I said, replacing FOV with focal length, and things like that for you so you don't have to do the work, as if I were speaking to a child:

And you don't realize that each time you change what you, personally, care about in equivalence, be it an equivalent DOF/aperture or equivalent ISO speed/amount of noise, that all the other parts change. So it doesn't matter... if you want to get the equivalent DOF/aperture between two lenses in two different formats, you will NOT be able to get the same ISO/noiselevel+shutter/exposure+focallength/FOV. If you care about having the equivalent ISO/noiselevel between two formats, you will not have the same DOF/aperture+shutter/exposure+focallength/FOV. If you care about the same focal length/FOV between formats, you won't have the same ISO/noiselevel+shutter/exposure+DOF/aperture. It's simply mathematically impossible. And until you understand this point I'm making, you'll continue saying the same things. There's still no point to trying to make-equivalent all the things you've talked about, because all the other things change... there is no "unified theory" of equivalence, and you're changing your qualifiers each time to make it look like there is.


Now with that in mind, explain how what you said here:
QuoteQuote:
Exactly. That's because ISO and focal length ae *not* among of the components of the equivalence - *noise* and "field of view" are. What are ISO and focal length but numbers to me? I don't care about *numbers*; I care about noise and field of view -thing I can see in the real world photographs I take.
So I don't care if I can't get the combination you list above, because it's not the combination I am interested in. I *can* get the same DOF, noise, shutter, and FOV, by simply using the focal lengths and apertures suggested by equivalence. And equivalence furthermore tells me how to to get an *improvement* in one or more of those areas, and what price I'll pay in terms of the other areas. That's what makes it of practical value.
makes any sense or has any relevance, and wasn't just a tactic to degrade and reduce this discussion further...
12-22-2009, 10:23 PM   #178
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QuoteOriginally posted by cousinsane Quote
A F2.8 lens will always be a F2.8 lens, I think we can all agree on that.

The "equivalent aperture" thing only applies to DOF.

What's there to argue about?
Exactly. It has no effect on shutter speed either, between FF and APS-C - only DOF, unless I'm misunderstanding what the actual argument is about.

Also, what does print size have to do with DOF? It's about sensor size.....




.

Last edited by jsherman999; 12-22-2009 at 10:31 PM.
12-22-2009, 10:31 PM   #179
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QuoteOriginally posted by jsherman999 Quote
Exactly. It has no effect on shutter speed either, between FF and APS-C - only DOF, unless I'm misunderstanding what the actual argument is about.
Marc disagrees. He says all the other parts you can equivalise matter just as much (moreso, actually -- he's stated he doesn't care about DOF nearly as much as noise). So yeah, I don't think there's really anything to get... it's just bickering for the sake of bickering...

...it's like writing a 40-page thesis on "The Properties of Doubling" and starting it like "Eons ago, when man first set out upon this planet, he was known to hunt and gather food. Until one day, man discovered that if he had twice as much food, it would last twice as long! And so, the Theory of Doubling first grabbed hold of its roots." and including things like "The Properties of Doubling can be seen all around you, if only you're smart enough to look -- some grocery stores will double coupons for you, which saves you money; if you work twice as long at your job, you will make twice as much money, making you richer; and if you have one car, you can get another one by simply using the tenets of the Theory of Doubling! It's amazing how this mysterious property has implications in our every day lives, isn't it?".

And then saying "no, you just don't understand the Theory of Doubling properly; obviously if you did you would see where you're wrong" when other people say how dumb of a thing it is to talk about.
12-23-2009, 04:50 AM   #180
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QuoteOriginally posted by jsherman999 Quote
Exactly. It has no effect on shutter speed either, between FF and APS-C - only DOF, unless I'm misunderstanding what the actual argument is about.

Also, what does print size have to do with DOF? It's about sensor size.....
What you and cousinsane and Wheatfield, wallyb and I seem to agree on easily, looks like being too simple for others to accept. That is fine, because everybody is entitled to his own views. Mathemeatically many things in this thread are correct. Except the whole noise equivalence, I like to add. The noise cannot be taken into accoun, asw it is an highly individual property of any single camera.

One could, as Marc does, argue, that "equivalence" can be applied as a guardline. May be, but I find this concept wholly obsolete, as (considering the diversity of noise patterns and intensities in different cameras) there cannot be made up any single, valid and recreatable rule to sum this diversity.

I find some simple rules much more relevant:
– noise increases, while photo site size on a sensor decreases
– noise increases with increased sensor sensitivity

That's all, what there is about noise. The "equivalence theory" applied to noise is also misleading, as cameras or any RAW converter apply different noise reduction on top, which even makes any generalized numerical approach meaningless.

One point to clarify though: DOF is not really a property of anything. It is just a mere convention of what looks acceptably in focus (aka "sharp") to a viewer in final print. This assumes, that prints are usually (therefor it really all is convention) viewed from a typical viewing distance app. the diagonal of that print.

In reality that means, that details smaller than 1 arcminute are small enough to not be resolved by the human eye - and that is the "sharpness limit".

Then the Circle of Least Confusion is calculated backward from that 1-arcminute-limit to the film or sensor size. This is done, because the final print would be reached by different magnifications from those different film/sensor formats. If you calculate backwards from the typical 1-arcmin resolving power of the eye you arrive for example at an acceptable Circle of Least Confusion of 0.025mm for 35mm format. The larger the format, the smaller the magnification at the print stage and the larger the acceptable Circle of Least Confusion can get.

Ben

Last edited by Ben_Edict; 12-23-2009 at 07:22 AM.
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