Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Started Jun 16, 2014 | Discussions
bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
2

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there, the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests.

-- hide signature --

Bob

bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Anders W wrote:

If you can scale down manufacturing tolerances by a factor 2

Why wouldn't manufacturing tolerances scale?

That is such a ridiculous question, if just you stop to think about it. Every manufacturing process has an associated set of tolerances. So, if you use the same process to produce a smaller product, you are not scaling the tolerances. If on the other hand you develop the tolerances so as to be able to scale them for the smaller product, then that finer tolerance process is available also for the larger product. The exception is only if the smaller size itself allows some change in the process which provides for smaller tolerances.

-- hide signature --

Bob

Just another Canon shooter
Just another Canon shooter Veteran Member • Posts: 4,691
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
2

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

You cited a formula yesterday that you do not understand,

What makes you think I do not understand it?

that proves you wrong.

The formula says nothing about diffraction versus aberrations. It just says something about the way lens resolution and sensor resolution combine into image resolution.

Combine or one limits resolution only?

It follows from the formula that image resolution increases when either lens or sensor resolution increases.

Then I would at least remove the boldface from the quote above, in red.

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noirdesir Forum Pro • Posts: 13,586
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

In a theory where you ignore diffraction, diffraction has no effect.

bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

noirdesir wrote:

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

In a theory where you ignore diffraction, diffraction has no effect.

I suppose that is true.

-- hide signature --

Bob

Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

You cited a formula yesterday that you do not understand,

What makes you think I do not understand it?

that proves you wrong.

The formula says nothing about diffraction versus aberrations. It just says something about the way lens resolution and sensor resolution combine into image resolution.

Combine or one limits resolution only?

It follows from the formula that image resolution increases when either lens or sensor resolution increases.

Then I would at least remove the boldface from the quote above, in red.

There is no boldface in red. And I see no reason to remove the boldface there is based on the formula or what I just said about it. As already pointed out, the formula says nothing about diffraction versus aberrations.

 Anders W's gear list:Anders W's gear list
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Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

There is always photon noise and read noise. Does that prevent us from isolating their effect on image quality?

 Anders W's gear list:Anders W's gear list
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Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
2

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

 Anders W's gear list:Anders W's gear list
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bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
2

Anders W wrote:

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

There is always photon noise and read noise. Does that prevent us from isolating their effect on image quality?

Change the topic, why don't you? You say that in optical theory there is a lens limited by lens aberrations only. No, there isn't. You might say that in some circumstances the effects of diffraction are small enough to be ignored, but that is a matter of analytical practice, not theory.

I think you just like arguing, Anders, because you could have quite easily clarified your meaning to JACS and stopped there, instead of insisting that your obviously incorrect statement was correct.

-- hide signature --

Bob

bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here. If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

-- hide signature --

Bob

Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
3

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

There is always photon noise and read noise. Does that prevent us from isolating their effect on image quality?

Change the topic, why don't you?

I hoped you might see the analogy, but apparently I was mistaken. So let me translate: The fact that certain factors are always present does not prevent us from isolating their impact.

You say that in optical theory there is a lens limited by lens aberrations only. No, there isn't. You might say that in some circumstances the effects of diffraction are small enough to be ignored, but that is a matter of analytical practice, not theory.

I think you just like arguing, Anders, because you could have quite easily clarified your meaning to JACS and stopped there, instead of insisting that your obviously incorrect statement was correct.

You might remember this paper by Cossairt et al. On p. 3 they express the same thought that I expressed above.

"In conventional lens design, resolution is limited by the spot size of the lens. For a lens with aberrations, spot size increases linearly with the scale of the lens."

Would you say Cossairt et al. speak about the impact of aberrations only in the passage I quote or are they talking about the joint impact of aberrations and diffraction?

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bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

There is always photon noise and read noise. Does that prevent us from isolating their effect on image quality?

Change the topic, why don't you?

I hoped you might see the analogy, but apparently I was mistaken. So let me translate: The fact that certain factors are always present does not prevent us from isolating their impact.

You are still changing the topic. That might have been a sensible answer to give to JACS rather than 'in optical theory there is'. However, you chose differently. Only you know why.

-- hide signature --

Bob

Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
2

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here.

So you have no data and no data analysis to back up your claim.

If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

You made an assertion. I didn't. So you carry the burden of proof. But here is an example as a starting point:

http://www.dpreview.com/forums/post/53893177

 Anders W's gear list:Anders W's gear list
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Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

Just another Canon shooter wrote:

Anders W wrote:

"What is known based on the laws of optics is that if we take a lens design for a certain format, say a 50/1.8 for FF, and scale it down in all relevant dimensions so as to make 25/1.8 for MFT, the two lenses will deliver the same resolution if we measure per image diagonal (and the MFT lens twice as much as the FF lens if we measure per mm) at the same f-stop as long as resolution is limited by lens aberrations only."

There is no such thing as limited by lens aberrations only.

In optical theory there is.

No, there is not.

Yes there is.

Anders, please cite this 'optical theory'. So far as I know, there is always diffraction. How is any lens not subject to diffraction?

There is always photon noise and read noise. Does that prevent us from isolating their effect on image quality?

Change the topic, why don't you?

I hoped you might see the analogy, but apparently I was mistaken. So let me translate: The fact that certain factors are always present does not prevent us from isolating their impact.

You are still changing the topic.

I am perfectly on topic. You questioned my assertion and I explained its basis.

That might have been a sensible answer to give to JACS rather than 'in optical theory there is'. However, you chose differently. Only you know why.

I substantiate my claims to the extent that substantiation is asked for as I just did. If JACS had asked for it, I would have done him the same favor as I did you. But he didn't.

 Anders W's gear list:Anders W's gear list
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Just another Canon shooter
Just another Canon shooter Veteran Member • Posts: 4,691
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Anders W wrote:

I hoped you might see the analogy, but apparently I was mistaken. So let me translate: The fact that certain factors are always present does not prevent us from isolating their impact.

The part that you keep ignoring, is that their (diffraction) impact is different for the two cases we discuss.

After a lot of dancing, you are trying to change your statement to something like this: If we can perfectly scale a lens and consider the geometric optics theory only, the projected images scale by the same factor, as well. Duh! Do you really think that we are still discussing whether if you can shrink something, it shrinks?

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Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

bobn2 wrote:

Anders W wrote:

If you can scale down manufacturing tolerances by a factor 2

Why wouldn't manufacturing tolerances scale?

That is such a ridiculous question, if just you stop to think about it. Every manufacturing process has an associated set of tolerances. So, if you use the same process to produce a smaller product, you are not scaling the tolerances. If on the other hand you develop the tolerances so as to be able to scale them for the smaller product, then that finer tolerance process is available also for the larger product. The exception is only if the smaller size itself allows some change in the process which provides for smaller tolerances.

See my reply to noirdesir here, penultimate section:

http://www.dpreview.com/forums/post/53893177

 Anders W's gear list:Anders W's gear list
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knickerhawk Veteran Member • Posts: 6,055
Re: Reply to Just another Canon shooter

Just another Canon shooter wrote:

knickerhawk wrote:

By the way, he was also wrong about the blue channel being the noisiest. In the uniform gray areas of the 6D studio scene shot, the red channel is both visibly noisier and statistically noisier (per std. dev. measurements).

And you could never understand the differences between RAW blue, sRGB blue, blue color, what a difference the RAW conversion can do, etc. The blue square in the 6D crop just looks much noisier than the red one in the ACR conversion, and in the DXO one; and how this relates to what you see in gray - I will leave that for you as an exercise.

Once again, your eyes are letting you down.  The blue patch and the red patch look to me to have more less identical amounts of noise.  The composite std. dev. measures for them are virtually identical as well.  But it's not just composite behavior which is very similar.  Below are samples from the two color patches.  I've taken the red channel from the red patch and the blue channel from the blue patch and placed them side by side below.  Which is which?

bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here.

So you have no data and no data analysis to back up your claim.

If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

You made an assertion. I didn't. So you carry the burden of proof. But here is an example as a starting point:

http://www.dpreview.com/forums/post/53893177

Well, I considered picking an example like that, but it takes time and doesn't really 'prove' anything at all, does it? But, if you are interested in bogus 'statistical' analysis, then try looking at DxOmark rankings. So, for instance if we filter the lens test data by MP, as follows:

Then you'll find that lenses ranked 1-368 are FF lenses, then we get the Panasonic Leica DG Nocticron 42.5mm F1.2 ASPH at 369. There is some duplication there down to same lens different camera, but there's little point spending a lot of time cleaning up an 'analysis' like that.

-- hide signature --

Bob

bobn2
bobn2 Forum Pro • Posts: 61,165
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Anders W wrote:

bobn2 wrote:

Anders W wrote:

If you can scale down manufacturing tolerances by a factor 2

Why wouldn't manufacturing tolerances scale?

That is such a ridiculous question, if just you stop to think about it. Every manufacturing process has an associated set of tolerances. So, if you use the same process to produce a smaller product, you are not scaling the tolerances. If on the other hand you develop the tolerances so as to be able to scale them for the smaller product, then that finer tolerance process is available also for the larger product. The exception is only if the smaller size itself allows some change in the process which provides for smaller tolerances.

See my reply to noirdesir here, penultimate section:

http://www.dpreview.com/forums/post/53893177

No connection with the question of scalability of tolerances at all. Linking irrelevant posts, implying that you had made some response to the point already is a most dishonest mode of argumentation.

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Bob

Anders W Forum Pro • Posts: 21,468
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Ulric wrote:

Anders W wrote:

The post of yours that began this exchange in the previous thread was:

http://www.dpreview.com/forums/post/53861976

"Additionally there is one inherit advantage larger formats have over smaller ones: enlargement factor. A large format image needs to be enlarged less than a medium format image, which needs to be enlarged less than FF image which needs to be enlarged less than APS-C image which needs to be enlarged less than m4/3 image which needs to be enlarged less than cell phone image and when less enlargement is needed, the lens is stressed less, thus the lens can be of lesser quality to achieve the same image quality."

Exactly what do you mean by "stressed less" and "lesser quality" here? And in what way does the "lesser quality" actually translate into an "inherent advantage of larger formats"?

The larger format lens does not have to resolve as many lines per millimeter on the image plane, thus it can be (but need not be) optically inferior to achieve the same output image quality compared to a smaller format lens. The reason is in the lesser need for enlargement from the image in the image plane to the output image of arbirtary size.

OTOH, what matters is not resolution per millimeter but per image, and the larger format lens has to perform over a larger image circle. It evens out.

In practice, no it doesn't - the advantage is to the larger image circle.

On what grounds?

On the grounds of that's how it is in practice, never mind any theoretical arguments.

OK. What's the evidence?

Plenty of it out there,

I didn't ask how much of it there was. I asked you which evidence.

the larger image circle generally produces higher resolution (normalised to frame size) in practice on most of the lens tests

Based on what statistical analysis of which lens test data?

Based on observation. Which is what we tend to do around here.

So you have no data and no data analysis to back up your claim.

If you wish to make a counter assertion, do you have a suitable statistical analysis to back that up?

You made an assertion. I didn't. So you carry the burden of proof. But here is an example as a starting point:

http://www.dpreview.com/forums/post/53893177

Well, I considered picking an example like that, but it takes time and doesn't really 'prove' anything at all, does it?

More than the one you refer to below which is systematically biased.

But, if you are interested in bogus 'statistical' analysis, then try looking at DxOmark rankings. So, for instance if we filter the lens test data by MP, as follows:

Then you'll find that lenses ranked 1-368 are FF lenses, then we get the Panasonic Leica DG Nocticron 42.5mm F1.2 ASPH at 369. There is some duplication there down to same lens different camera, but there's little point spending a lot of time cleaning up an 'analysis' like that.

What is the relationship between those lens rankings and the factor we are trying to isolate in this discussion: Lens resolution.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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