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05-25-2014, 07:44 PM   #121
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QuoteOriginally posted by eyeswideshut Quote
I didn't know this paradigm was so powerful.
Glad we could help.

05-26-2014, 12:20 AM   #122
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QuoteOriginally posted by filoxophy Quote
Are we done here?
Pretty much.
05-26-2014, 01:07 PM   #123
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QuoteOriginally posted by eyeswideshut Quote
This is getting hillarious! I fear YOU do not understand equivalence. NO ONE is redifining optics. It is the sensor size that redifines the depth of field of that lens, but in terms of aov the statement from b&h is absolutely correct. And as EVERYBODY knows, focal length has been used for decades (centuries?) as shorthand for aov. Only pedants or equivalists can quibble with that.
Now you're just trolling. Achromatic lens have not been around for "centuries". Sensor size does not change the DoF that is projected by the lens.

Nobody is arguing that FoV (aov) is not "equivalent". The entire conversation has been about aperture. If you read the thread or saw the video you would know this. Since aperture is a function of focal length, you can't change the focal length and not change the area of the aperture.
05-27-2014, 03:16 AM   #124
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QuoteOriginally posted by Winder Quote
Now you're just trolling. Achromatic lens have not been around for "centuries".
Before accusing me of trolling you should do a little research. You will then find that achromats were invented in the 1730's and finally patented in 1758. That's centuries in my book - but your math might vary of course. I merely wondered aloud when focal length as shorthand for angle of view made its appearance. Did it come into play as 35mm photography became dominant or was it used before already? I really don't know. Might be an engaging topic for a little research - anyone?
But tell me, what has the achromatic doublet got to do with any of this anyway? Are you suggesting different equivalencies for triplets? Double Gaussian designs? Do respond, I'd be interested to know.

QuoteQuote:
Sensor size does not change the DoF that is projected by the lens.
Bingo! There is hope. Now if only you would get into the habit of reading AND comprehending others before responding, you would have no need to accuse me of trolling. To quote myself:

"This is getting hillarious! I fear YOU do not understand equivalence. NO ONE is redifining optics. It is the sensor size that redifines the depth of field of that lens, but in terms of aov the statement from b&h is absolutely correct. And as EVERYBODY knows, focal length has been used for decades (centuries?) as shorthand for aov. Only pedants or equivalists can quibble with that. "

I have to admit that my statement is not quite as clear as it should have been. I should of course say equivalent lens (in terms of aov), for which we then adjust aperture to get the equivalent depth of field etc etc. But that should be pretty obvious from everything in this thread. Let me quote Joseph James who put it quite nicely:

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens). However, the effect of both the focal length and the f-ratio on the visual properties of the photo very much depend on the sensor, and scale in direct proportion to the size of the sensor

When you say that the dof projected by the lens does not change you are simply abandoning your own equivalence portion of the argument and returning to KUNZITE's position. Funny turn of events that is.

QuoteQuote:
Nobody is arguing that FoV (aov) is not "equivalent". The entire conversation has been about aperture. If you read the thread or saw the video you would know this. Since aperture is a function of focal length, you can't change the focal length and not change the area of the aperture.
Not quite. The argument is that an expression of focal length in terms of some crop factor (as sometimes practiced by the industry) is disingenuous and misleading because it fails to adjust aperture in terms of the crop factor as well - which is needed if (but ONLY if) equivalence of photographic output is the object. So now you have brought in the equivalence portion again and an understanding of aperture as relative opening or f-stop is no longer sufficient. You now want to talk about total light gathered as opposed to light gathered per square unit and ISO and SNR and on and on...

I have said this before, there is nothing wrong with all of this equivalence stuff. Just know when it is approprite and when it is merely irksome.
Leaving it out and bringing it back in ad libitum merely leads to fogging of my brain - and perhaps other's as well.

05-27-2014, 06:30 AM   #125
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QuoteOriginally posted by eyeswideshut Quote
Before accusing me of trolling you should do a little research. You will then find that achromats were invented in the 1730's and finally patented in 1758. That's centuries in my book - but your math might vary of course. I merely wondered aloud when focal length as shorthand for angle of view made its appearance. Did it come into play as 35mm photography became dominant or was it used before already? I really don't know. Might be an engaging topic for a little research - anyone?
But tell me, what has the achromatic doublet got to do with any of this anyway? Are you suggesting different equivalencies for triplets? Double Gaussian designs? Do respond, I'd be interested to know.
Achromtatic lenses were use for telescopes in the 1700's, but not until 1939 for camera lenses. We're talking about camera here.
QuoteOriginally posted by eyeswideshut Quote
Not quite. The argument is that an expression of focal length in terms of some crop factor (as sometimes practiced by the industry) is disingenuous and misleading because it fails to adjust aperture in terms of the crop factor as well - which is needed if (but ONLY if) equivalence of photographic output is the object. So now you have brought in the equivalence portion again and an understanding of aperture as relative opening or f-stop is no longer sufficient. You now want to talk about total light gathered as opposed to light gathered per square unit and ISO and SNR and on and on...
You obviously have not been reading the thread.
05-27-2014, 06:53 AM   #126
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QuoteOriginally posted by Winder Quote
Achromtatic lenses were use for telescopes in the 1700's, but not until 1939 for camera lenses. We're talking about camera here.

You obviously have not been reading the thread.
Wrong. Achromats were used in photography from the start (BTW, that would have been 1839 not 1939).
History of photographic lens design - Wikipedia, the free encyclopedia

But I had also asked you to explain what the significance of achromatic lenses is with respect to equivalence. Still waiting.
05-27-2014, 07:43 AM   #127
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QuoteOriginally posted by eyeswideshut Quote
Wrong. Achromats were used in photography from the start (BTW, that would have been 1839 not 1939).
History of photographic lens design - Wikipedia, the free encyclopedia

But I had also asked you to explain what the significance of achromatic lenses is with respect to equivalence. Still waiting.
Yes. That was a typo 1839.

Its not until after the adaptation of achromatic lenses to photography that we see any significant variations of focal length of the optic. If you don't have different focal lengths then you can't have a conversation about lens equivalence.

You're comment that:
QuoteOriginally posted by eyeswideshut Quote
And as EVERYBODY knows, focal length has been used for decades (centuries?) as shorthand for aov.
When you throw "centuries" in with a question mark at the end of its a give away that you don't really know what you're talking about. Photography itself has not been around for "centuries", so it pretty hard to take you seriously.
05-27-2014, 08:18 AM   #128
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QuoteQuote:
Its not until after the adaptation of achromatic lenses to photography that we see any significant variations of focal length of the optic. If you don't have different focal lengths then you can't have a conversation about lens equivalence.
The very first photographic lens by Monsieur Chevalier was already thus corrected. Also there were different size plates and different focal lengths from the beginning. That's what I mean with 'centuries'. If you had been so inclined, you could have talked equivalence even in the nineteenth century. Of course no one did. Because it's not very useful. But that is my point after all.

QuoteQuote:
When you throw "centuries" in with a question mark at the end of its a give away that you don't really know what you're talking about. Photography itself has not been around for "centuries", so it pretty hard to take you seriously.
Winder, that's where reading comprehension comes in handy. I'll just repeat myself in the hope that repetiton will aid your understanding:

"Before accusing me of trolling you should do a little research. You will then find that achromats were invented in the 1730's and finally patented in 1758. That's centuries in my book - but your math might vary of course. I merely wondered aloud when focal length as shorthand for angle of view made its appearance. Did it come into play as 35mm photography became dominant or was it used before already? I really don't know. Might be an engaging topic for a little research - anyone?
But tell me, what has the achromatic doublet got to do with any of this anyway? Are you suggesting different equivalencies for triplets? Double Gaussian designs? Do respond, I'd be interested to know."

05-27-2014, 09:14 AM   #129
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QuoteOriginally posted by eyeswideshut Quote
I thought the rebuttal was pretty funny actually.
Me too
.
QuoteQuote:
Only problem is that ... Only if we accept the premise of wanting to create equal output in terms of the five parameters identified by Joseph James does equivalence even come into play.
No, no, no, no, no. And I'm not picking on you, I think 50% of the people who encounter equivalence get this wrong. They think it's somehow mandating that everyone needs to or wants to create equivalent images when they move between formats. Not what it's saying, not what it's there for.

It's not "you must want to create equivalent images, so here's how."

Its: "here's how the two formats in question relate to each other, using the method of creating equivalent images to describe the relationship."

It's F=MA. It's not "F always needs to equal MA, so you need to adjust M or A accordingly to equal a certain F."

---------- Post added 05-27-14 at 10:19 AM ----------

QuoteOriginally posted by Kunzite Quote
Who on Earth would attempt to use "equivalence" between Q and 645z? Aren't you buying those cameras for completely different purposes?
Yes, But some people buy the Q or the Nikon 1 or something similar to do something like shoot telephoto, and if they listen to the wrong camera store clerk or forum denizen, they might no realize the limitations involved in doing that. Or, they might buy a FF system to shoot birds when all they care about is the stuff the Q could bring.

Equivalence can really, really be their friend! It can save them from buying something they don't really want - whether that's the Q, or the aps-c (or FF) system.
05-27-2014, 09:53 AM   #130
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Comparing "equivalence" to Newton's second law of motion, wow! And with an analogy that makes no sense.
F is equal (not equivalent) to mass multiplied by acceleration - that is, in Newtonian physics. There is no choice about it; that's how things are.
What is the claim here? That "equivalence" is not mandatory, but it's some kind of law?

By the way, I was repeatedly told I attempted to create equivalent images when I moved between formats. And the idea of only caring about a subset (e.g. angle of view) while ignoring other parameters (e.g. DoF) is not accepted.
For a thing which is not mandated, it's weird that people are going all out promoting and enforcing it.
05-27-2014, 10:21 AM   #131
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QuoteOriginally posted by eyeswideshut Quote
Funny, but dude get with the program. A Canon EF 24-70mm f/4.0 is all he needs to show his friend Lisa who is boss. I think you had better go back and study the tenets of Equivalism
Actually a used $285 Tamron 28-75 f/2.8 on FF will do most of the boss-work there

---------- Post added 05-27-14 at 11:29 AM ----------

QuoteOriginally posted by Kunzite Quote
F is equal (not equivalent) to mass multiplied by acceleration - that is, in Newtonian physics. There is no choice about it; that's how things are.
EXACTLY. And so it is with equivalence. You have no choice in the matter - it's the way it is. You don't need to care about it if you don't plan on shooting more than one format ever, but you can't will it away just because it really makes you angry. Please, please, please read the JJ link and Falk Lumo's paper. If you want, I can supply some dpreview threads where those authors engaged in some explanations as well.


.
QuoteQuote:
By the way, I was repeatedly told I attempted to create equivalent images when I moved between formats. And the idea of only caring about a subset (e.g. angle of view) while ignoring other parameters (e.g. DoF) is not accepted.
For a thing which is not mandated, it's weird that people are going all out promoting and enforcing it.
Sorry you were treated so ill.

.

Last edited by jsherman999; 05-27-2014 at 10:32 AM.
05-27-2014, 10:40 AM   #132
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QuoteQuote:
No, no, no, no, no. And I'm not picking on you, I think 50% of the people who encounter equivalence get this wrong. They think it's somehow mandating that everyone needs to or wants to create equivalent images when they move between formats. Not what it's saying, not what it's there for.

It's not "you must want to create equivalent images, so here's how."

Its: "here's how the two formats in question relate to each other, using the method of creating equivalent images to describe the relationship."
Believe it or not, I'm in agreement with you. I've been (trying to ) say that Joseph James' arguments seem sound and useful as long as his original premise (producing equivalent output) is borne in mind. If that is not applicable or desired, then equivalence has little bearing and can safely be ignored. So it's not that one "must want to create equivalent images" but rather that granted one wants to create equivalent images with different formats, here's what got to be mindful of and here's how the five parameters interelate.

What bugs me though, I tried to point out in my 'black cats in coal mines' example. Until a few years ago we were all happy to convert focal length from one format into 35mm terms and thought nothing of it. Equally, none of us felt constrained to adjust for depth of field because no one thought equivalence of outcome was the object of discussion. Now, some people will jump in and demand that anyone who says A must also say B - and that of course is ONLY the case when equivalence of outcome desired, which in the context of this format and that format is rarely the case. There are many, many reasons to chose one over another, most totally unrelated to equivalence. And of course it usually goes downhill from there. Until in the end it is a 'my gear is better than your gear because you would need a f/0.3 lens to match mine' brawl.
Cheers
05-27-2014, 10:57 AM   #133
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QuoteOriginally posted by eyeswideshut Quote
Believe it or not, I'm in agreement with you. I've been (trying to ) say that Joseph James' arguments seem sound and useful as long as his original premise (producing equivalent output) is borne in mind. If that is not applicable or desired, then equivalence has little bearing and can safely be ignored. So it's not that one "must want to create equivalent images" but rather that granted one wants to create equivalent images with different formats, here's what got to be mindful of and here's how the five parameters interelate.
Yes, thank you.

QuoteQuote:
...What bugs me though, I tried to point out in my 'black cats in coal mines' example. Until a few years ago we were all happy to convert focal length from one format into 35mm terms and thought nothing of it. Equally, none of us felt constrained to adjust for depth of field because no one thought equivalence of outcome was the object of discussion. Now, some people will jump in and demand that anyone who says A must also say B - and that of course is ONLY the case when equivalence of outcome desired, which in the context of this format and that format is rarely the case. There are many, many reasons to chose one over another, most totally unrelated to equivalence. And of course it usually goes downhill from there. Until in the end it is a 'my gear is better than your gear because you would need a f/0.3 lens to match mine' brawl.
Cheers
Well said, I can't really disagree.

In my experience, though - and maybe this is just what I've noticed - a smaller format shooter (usually m43,) tries to establish some form of parity or superiority first, in a sketchy or misrepresented situation where none exists, and then equivalence is whipped out to bring the discussion back to facts, and then it goes downhill from there. Its a 'he started it' situation. Then, a lot of folks start to think equivalence is this bad thing that makes people argue and feel bad. It gets a bad rap.

Equivalence should not matter to 90% of aps-c shooters. If you don't ever plan to shoot or buy into another format, just ignore it.

.
05-27-2014, 11:10 AM   #134
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I don't think one-format-only shooters should ignore it. Or at least, people new to any format shouldn't ignore equivalence. People who are buying a camera should know what capabilities they're getting and why.

Knowing equivalence will kill the 'you should get a smaller format because it combines large DOF with low noise' myth.... that otherwise will never die.

Alternatively it should also kill the 'you should get a larger format because it'll produce a picture with less noise than a smaller format camera'... that always ignores that the picture isn't the same, too.
05-27-2014, 11:33 AM   #135
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QuoteOriginally posted by eyeswideshut Quote
"Before accusing me of trolling you should do a little research. You will then find that achromats were invented in the 1730's and finally patented in 1758.
And as I pointed out we are talking about camera lenses not telescopes. They don't get adapted to camera lenses until 1839. Photographers have not been having this discussion for centuries.

QuoteOriginally posted by eyeswideshut Quote
The very first photographic lens by Monsieur Chevalier was already thus corrected
His first lenses that he produced for photography were uncorrected single element lenses. If you can find a link to a pre-1839 "corrected" lens I would love to see it.
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