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

Started Jun 16, 2014 | Discussions
knickerhawk Veteran Member • Posts: 6,018
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Just another Canon shooter wrote:

Can you tell me what is written here, with the small letters? Nevermind, I can read it now. Even better here.

Let's just say I have a lot of respect for Bob and am far more interested in his response than yours...and leave it at that.

knickerhawk Veteran Member • Posts: 6,018
Re: I am not sure I read it correctly ..
1

Sergey_Green wrote:

knickerhawk wrote:

If we throw out the higher resolution sensors and adjust for the many more tested combinations, the number is much smaller than 368, but the problem doesn't end there. The dxo lens score isn't equivalence based. For instance, the highest score for the Nikkor 24-70mm f/2.8 on a 16mp Nikon body is 25 and the highest score for the Oly 12-40mm f/2.8 on a 16mp m43 body is 20. Looks like the Oly lens is inferior to the Nikkor by a significant margin, doesn't it? But look what happens when we set the respective dxo score maps at equivalent aperture settings:

Or if it is clear at all. Are you saying at equivalent (stopped down) aperture 24-70/2.8 will do worse, or that 12-40/2.8 when opened up "more" will perform even better? Can you please clarify what you are saying here?

Consider it a homework assignment and figure out the implications for yourself, Sergey.

That tells a rather different story than the basic score, doesn't it?

..

\

Sergey_Green
Sergey_Green Forum Pro • Posts: 11,928
If it is important ..

knickerhawk wrote:

Consider it a homework assignment and figure out the implications for yourself, Sergey.

The equivalent settings with most used apertures will often benefit larger formats. So I can't really see what it is you are trying to show with your post. Unless you mean something entirely different.

-- hide signature --

- sergey

Sergey_Green
Sergey_Green Forum Pro • Posts: 11,928
Bob says ..

knickerhawk wrote:

bobn2 wrote:

..

If we throw out the higher resolution sensors and adjust for the many more tested combinations, the number is much smaller than 368, but the problem doesn't end there. The dxo lens score isn't equivalence based. For instance, the highest score for the Nikkor 24-70mm f/2.8 on a 16mp Nikon body is 25 and the highest score for the Oly 12-40mm f/2.8 on a 16mp m43 body is 20. Looks like the Oly lens is inferior to the Nikkor by a significant margin, doesn't it? But look what happens when we set the respective dxo score maps at equivalent aperture settings:

That tells a rather different story than the basic score, doesn't it?

Try 24-105/4 Sigma, where f/5.6 on the Olympus lines up with f/11 on the Sigma. Sigma looks better.

And while I seldom look at this stuff, I am tempted to add one single question here; does it mean Sigma is a better lens than 24-70/2.8? Hmm.

-- hide signature --

- sergey

knickerhawk Veteran Member • Posts: 6,018
Re: Bob says ..
1

Sergey_Green wrote:

knickerhawk wrote:

bobn2 wrote:

..

If we throw out the higher resolution sensors and adjust for the many more tested combinations, the number is much smaller than 368, but the problem doesn't end there. The dxo lens score isn't equivalence based. For instance, the highest score for the Nikkor 24-70mm f/2.8 on a 16mp Nikon body is 25 and the highest score for the Oly 12-40mm f/2.8 on a 16mp m43 body is 20. Looks like the Oly lens is inferior to the Nikkor by a significant margin, doesn't it? But look what happens when we set the respective dxo score maps at equivalent aperture settings:

That tells a rather different story than the basic score, doesn't it?

Try 24-105/4 Sigma, where f/5.6 on the Olympus lines up with f/11 on the Sigma. Sigma looks better.

You haven't defined which Canon body you're using, so I can't comment on the specific score map comparison you're offering above.  (It also looks like you're using a different score map for the Oly combo than I'm using.)

Apparently DXO has not measured the Sigma 24-105mm on a 16mp Nikon, so the closest apples-to-apples comparison available (resolution-wise) is to the Canon 6D. Despite the 4mp resolution "head start" we're giving the 6D+Sigma combo, the Oly combo holds up just fine here.

I must say, I feel a bit like I'm a guest at a seance and the message from the departed's spirit is getting garbled by the crackpot medium. Perhaps we should just wait until Bob returns to the living and let him respond directly?

Sergey_Green
Sergey_Green Forum Pro • Posts: 11,928
Boo ..

knickerhawk wrote:

..

I must say, I feel a bit like I'm a guest at a seance and the message from the departed's spirit is getting garbled by the crackpot medium. Perhaps we should just wait until Bob returns to the living and let him respond directly?

Something like that. As it was clear from the start, I did not even know what those colors meant when you cropped the numbers out. And why I should be comparing 24-70/2.8 at f/11 could not be even more puzzling to me. Most of the time it is between f/5.6 and f/7.1, or something like that.

For example, see, stopping 24-70 down is not necessary,

-- hide signature --

- sergey

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

knickerhawk wrote:

But look what happens when we set the respective dxo score maps at equivalent aperture settings:

That tells a rather different story than the basic score, doesn't it?

It tells you the story about a company which decided to dumb down the way to present their measurements in order to appeal to the "ordinary public"; in a rather successful way, apparently.

Did you notice that those charts are "accutance maps", whatever DXO means by that, measured in percentage of something (DXO decides that it is too much to tell us because they believe that we are not intelligent enough to understand it)? If you compare them in another undocumented metric, P-Mpix, those charts look like this:

12-40 on EM-1 vs. Nikon 24-70 on Df. The f-stop scale is in m43 eq. units

What does it tell us (in the Mpix metric)? First, the m43 combo has a huge gap - cannot do f/2.8-f/5.6 (the vertical axis is in m43 units, not FF ones). Of course, we knew that but this is the elephant in the room which should be noticed from time to time. Next, in the aperture range that the m43 combo can do, it is mediocre. In the very wide end kinda gets close somewhere around  f/5.6 (in FF terms) and that's about it.

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knickerhawk Veteran Member • Posts: 6,018
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Just another Canon shooter wrote:

knickerhawk wrote:

But look what happens when we set the respective dxo score maps at equivalent aperture settings:

That tells a rather different story than the basic score, doesn't it?

It tells you the story about a company which decided to dumb down the way to present their measurements in order to appeal to the "ordinary public"; in a rather successful way, apparently.

Remember, the reason I responded to Bob was to counter his criticism of Anders for not accepting at face value the "packaged" results from DXO.  I think you and I are actually pretty much in agreement on the questionable value of DXO's scores.  Likewise, I think we probably agree that the dumbing down of the lens data and packaging the data introduces unfortunate problems.  A naive reading of the scores (and score maps) fails to take some important factors (such as equivalence) into account and a more sophisticated reading of the scores appears to be impractical.  It's a shame really because there's a lot of useful data underlying these scores, maps and profiles.

Did you notice that those charts are "accutance maps", whatever DXO means by that, measured in percentage of something (DXO decides that it is too much to tell us because they believe that we are not intelligent enough to understand it)? If you compare them in another undocumented metric, P-Mpix, those charts look like this:

12-40 on EM-1 vs. Nikon 24-70 on Df. The f-stop scale is in m43 eq. units

What does it tell us (in the Mpix metric)? First, the m43 combo has a huge gap - cannot do f/2.8-f/5.6 (the vertical axis is in m43 units, not FF ones). Of course, we knew that but this is the elephant in the room which should be noticed from time to time. Next, in the aperture range that the m43 combo can do, it is mediocre. In the very wide end kinda gets close somewhere around f/5.6 (in FF terms) and that's about it.

Your reference to the P-Mpix maps is just another example of how misleading the presentation of the DXO data can be.  For instance, the information in the sharpness profile tab for the two lenses at f/2.8 for the Oly and f/5.6 for the Nikkor indicates that they perform quite similarly in the center (the Oly wins the horizontal measurement and the Nikkor wins the vertical and average of the two), but the Oly is better across the whole frame.  However, because the DXO P-Mpix score weights (in some unspecified way) center performance more than performance outside of the center, the 24-70 appears in the map to be a stronger performer.  Interestingly, the Panny 12-35mm has a slightly stronger (equivalent) center performance than either of the other two zooms being considered here, so it's not as if there is some insurmountable limitation on center accutance for the smaller format.

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

knickerhawk wrote:

Remember, the reason I responded to Bob was to counter his criticism of Anders for not accepting at face value the "packaged" results from DXO. I think you and I are actually pretty much in agreement on the questionable value of DXO's scores.

So is Bob.

Your reference to the P-Mpix maps is just another example of how misleading the presentation of the DXO data can be. For instance, the information in the sharpness profile tab for the two lenses at f/2.8 for the Oly and f/5.6 for the Nikkor indicates that they perform quite similarly in the center (the Oly wins the horizontal measurement and the Nikkor wins the vertical and average of the two), but the Oly is better across the whole frame.

Those are "acutance maps", whatever that means, as a percentage of who knows what; instead of P-Mpix maps, whatever that means.

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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

Just another Canon shooter wrote:

knickerhawk wrote:

Remember, the reason I responded to Bob was to counter his criticism of Anders for not accepting at face value the "packaged" results from DXO. I think you and I are actually pretty much in agreement on the questionable value of DXO's scores.

So is Bob.

If that's so, why does he cite them when asked for evidence to substantiate his "theory"?

And why doesn't he have anything but an ad-hominem attack to offer in response when appropriately criticized for his choice of data?

http://www.dpreview.com/forums/post/53901097

Your reference to the P-Mpix maps is just another example of how misleading the presentation of the DXO data can be. For instance, the information in the sharpness profile tab for the two lenses at f/2.8 for the Oly and f/5.6 for the Nikkor indicates that they perform quite similarly in the center (the Oly wins the horizontal measurement and the Nikkor wins the vertical and average of the two), but the Oly is better across the whole frame.

Those are "acutance maps", whatever that means, as a percentage of who knows what; instead of P-Mpix maps, whatever that means.

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knickerhawk Veteran Member • Posts: 6,018
Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
1

Just another Canon shooter wrote:

knickerhawk wrote:

Remember, the reason I responded to Bob was to counter his criticism of Anders for not accepting at face value the "packaged" results from DXO. I think you and I are actually pretty much in agreement on the questionable value of DXO's scores.

So is Bob.

That's certainly what I would hope.  Perhaps when he is reanimated here he can explain why he was critical of Anders for questioning the value of the DXO lens scores.

Your reference to the P-Mpix maps is just another example of how misleading the presentation of the DXO data can be. For instance, the information in the sharpness profile tab for the two lenses at f/2.8 for the Oly and f/5.6 for the Nikkor indicates that they perform quite similarly in the center (the Oly wins the horizontal measurement and the Nikkor wins the vertical and average of the two), but the Oly is better across the whole frame.

Those are "acutance maps", whatever that means, as a percentage of who knows what; instead of P-Mpix maps, whatever that means.

Well, to clarify, in your prior post you pasted the P-Mpix maps.  The "acutance maps" can be found under the Global Map and Field Map tabs.  It's all rather confusing and the precise relationship between the P-Mpix map and the other maps and the Profiles graphs is not decipherable (to me at least).

Anders W Forum Pro • Posts: 21,468
Here is how it actually works
3

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

http://www.dpreview.com/forums/post/53899308

To reiterate, as Cossairt et al. put it in the paper I link to in that post:

"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."

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT), the aberration-limited resolution on a per-image basis will be exactly the same at the same f-stop.

Consequently, the claim of yours above is incorrect. What it overlooks is the elementary fact that the loss of resolution due to aberrations in the 1 cm image will be proportionally smaller than in the 2 cm image for two lenses with exactly the same design but made to cover differently sized image circles.

However, the diffraction-limited as opposed to aberration-limited spot size does not scale in the manner described by Cossairt et al. Rather the diffraction-limited spot size remains the same at the same f-stop. Consequently, the smaller format has a disadvantage as far as diffraction is concerned.

The general implications of these two facts (the one regarding aberrations and the one regarding diffraction) can be illustrated graphically by means of the stylized graphs below (borrowed from a post where I demonstrated the same thing to bobn2 four months ago here).

The first graph shows how the two lenses (identical except for being scaled so as to yield image circles of different size) would generally compare at the same f-stop. At very wide apertures there would be very little difference since optical aberrations is the dominant factor in determining sharpness levels and diffraction hardly matters at all. The sharpness level will therefore be pretty much the same for MFT and FF alike. As we stop down, optical aberrations are reduced and diffraction starts to play a bigger role. Since FF has the benefit of less diffraction at any given f-stop, it will gradually get further and further ahead as diffraction becomes a more and more decisive factor and once we get to f/16, there will be a rather significant difference between the two systems.

View: original size

If, instead we compare at FF-equivalent f-stops (those f-stops where the level of diffraction, the DoF, and the total amount of light that falls on the sensor at the same shutter speed are the same), so that f/1 on MFT is compared with f/2 on FF, f/2 on MFT with f/4 on FF, and so on, it will be the other way around. At very wide apertures, the advantage of FF over MFT will be major rather than minor due to the optical aberrations at f/1 (MFT) being far more serious than those at f/2 (FF). As we stop down, the role of optical aberrations is again reduced and that of diffraction increased. Since diffraction at equivalent apertures is the same, the result is that the FF advantage is reduced to eventually reach a trifling level.

But it's your own logic. YOU were the one who started this discussion by noting that greater magnification comes with an unavoidable resolution penalty.

I state(ed) the following, nothing more:

  1. With a perfect sensor and a lens with aberrations we will have a limited resolution which can be measured in line pairs per millimiter on the image plane.
  2. What the resolution of the output image is depends on the crop factor and can be measured in line pairs by image height.

Do you agree or disagree?

The problem is that you only applied that penalty from an interim point in the magnification (i.e. the sensor plane) to the output display plane.

Huh! The lens draws an image with finite resolution. The more you have to enlarge it, the more the aberrations will show.

You didn't account for the "penalty" incurred between the lens and the sensor (i.e., the focal length).

Huh!

A Carl Zeiss Jena 35mm f/2.4 Flektogon has 35mm focal length regardless fo the crop factor.

With ideal perfect sensors a cropped sensor will turn a lower resolution output image on perfect output device than what a full frame sensor would do because you need to enlarge the image more, thus enlarge the aberrations more too (after all, there just part of the image).

If you change the lens or the optical configuration, that is your bussiness, but has nothing to do with the point. For example by using the focal reducer you're improving the optical configuration by reducing the aberrations (for example 1µm aberration on the image with a naked lens would reduce to 0.5µm aberration with a perfect 2x focal reducer). High quality focal reducer is certainly a better option in most cases than a conventional adapter.

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OP Truthiness Regular Member • Posts: 122
Re: Here is how it actually works

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

I'm not reallly that interested how lens X performs compared to lens Y regardles of how the lens Y is designed (perfectly scaled from X of whatever) as it is not the point and is often not relevant as scaling a lens perfectly doesn't necessarily achieve what one thinks it does, in practise, as the manufacturing tolerance issues etc. come to play.

knickerhawk Veteran Member • Posts: 6,018
Re: Here is how it actually works
1

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

I'm not reallly that interested how lens X performs compared to lens Y regardles of how the lens Y is designed (perfectly scaled from X of whatever) as it is not the point and is often not relevant as scaling a lens perfectly doesn't necessarily achieve what one thinks it does, in practise, as the manufacturing tolerance issues etc. come to play.

And round and round we go...

By the way, your reference to small sensors "stressing" lenses suggests a new name for the focal reducer that Brian Caldwell is developing. Instead of calling it the Metabones "Speedbooster" perhaps he should call it the Metabones "Stress Reducer."

http://www.lensrentals.com/blog/2014/06/the-glass-in-the-path-sensor-stacks-and-adapted-lenses

OP Truthiness Regular Member • Posts: 122
Re: Here is how it actually works

knickerhawk wrote:

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

I'm not reallly that interested how lens X performs compared to lens Y regardles of how the lens Y is designed (perfectly scaled from X of whatever) as it is not the point and is often not relevant as scaling a lens perfectly doesn't necessarily achieve what one thinks it does, in practise, as the manufacturing tolerance issues etc. come to play.

And round and round we go...

By the way, your reference to small sensors "stressing" lenses suggests a new name for the focal reducer that Brian Caldwell is developing. Instead of calling it the Metabones "Speedbooster" perhaps he should call it the Metabones "Stress Reducer."

So when you don't have an argument you go to ad hominem. Please grow up.

Anders W Forum Pro • Posts: 21,468
Re: Here is how it actually works
2

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

So what you now claim is merely that if a lens made for FF is used with MFT it will perform less well than if it is used with the format for which it was originally made. In what way is that trivial claim an inherent advantage of the larger format? All the lenses I use with MFT are made for MFT.

I'm not reallly that interested how lens X performs compared to lens Y regardles of how the lens Y is designed (perfectly scaled from X of whatever) as it is not the point and is often not relevant as scaling a lens perfectly doesn't necessarily achieve what one thinks it does, in practise, as the manufacturing tolerance issues etc. come to play.

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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

Just another Canon shooter wrote:

Anders W wrote:

My point is that the "enlargement theory" proposed in the OP of this thread is wrong. Whatever advantages the larger format has, that's not the way it gains them.

Using wrong arguments to disprove a wrong theory does not make you right.

I used the right argument to disprove the wrong theory and prove another one correct.

None of the posters here which are still active says that it is a simple matter of more enlargement.

May I remind you that you entered an exchange between me and posters who made claims based on enlargement that there were good reasons for me to question. Whether these posters are still active in the thread or not is secondary but at least one of them (the OP) has continued to post on that topic as you can see here (and subsequent posts in that subthread):

http://www.dpreview.com/forums/post/53901715

Rather, the simple truth is that it is easier, regardless of sensor size, to make an f/2.8 normal lens that performs well wide open than to make an f/1.4 normal lens that performs similarly well wide open. The aberrations you have to correct for decent performance are simply smaller at f/2.8 than at f/1.4 and that's it.

Right.

Good.

The lowly Canon 50/1.4 at f/4 beats the Panasonic 25/1.4 at f/2 by a comfortable margin (PZ) both in the center and at the borders,

Did you see the big sign on PZ's home page saying that their results are not comparable across sensors/platforms?

That is what you actually get in reality.

With the 25/1.4, yes. That's why I prefer the 20/1.7 (and the 1.7 to 2.0 range over 1.4).

Panasonic 25/1.4 on E-M5 (16 MP)

1.4 690/590

Canon 50/1.4 on 5D2 (21 MP)

2.8 920/690

See? The 25/1.4 is well behind. BTW, the figures are per picture height. Per diameter, you have to add 8% to the FF format.

As I said, I don't find much need for the shallow DoF that comes with a 50/1.4 wide open on FF and the lens is big and heavy.

And yet, you cannot tell just by looking at a few pictures which DOF is enough for you.

Of course I can.

Do you find the DOF below too shallow (sorry for the boring photo)?

Yes.

I'd much rather have the FL control (more lenses in my bag rather than in a drawer back home) that I get with MFT.

One good way to get FL control is to have a capable zoom (with less lenses in the bag). The m43 system has no meaningful answer to the FF f/4 zooms.

For my needs, the 12-40/2.8 is a meaningful answer. When I need the FF equivalent of f/4 or (or a bit wider) for subject isolation by background blur, I would usually use my 45/1.8 and/or 75/1.8. I prefer that to carrying a 70-200/4 FF zoom.

EDIT: DXOmark contradicts your claim that the 20/1.4 is sharper than the Canon 50/1.4 (as PZ does), by far, but you knew that, right?

As to PZ, I already notified you here

http://www.dpreview.com/forums/post/53900103

of the fact that you have apparently overlooked the big sign about non-comparability across platforms posted on their home page. As to DxO, things are pretty complicated as you have already recognized in your exchange with knickerhawk. If you have more to say about the matter, I suggest we continue the exchange there, i.e., here:

http://www.dpreview.com/forums/post/53921414

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OP Truthiness Regular Member • Posts: 122
Re: Here is how it actually works
1

Anders W wrote:

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

So what you now

I've claimed just this all the time. Maybe you just misunderstood?

claim is merely that if a lens made for FF is used with MFT it will perform less well than if it is used with the format for which it was originally made.

In what way is that trivial claim an inherent advantage of the larger format? All the lenses I use with MFT are made for MFT.

If the lenses are equally good, the larger format has an inherit advantage. This is what I claimed. If you scale the lenses perfectly down, you improve the lens as you reduce the aberrations.

The simple statement I made means that if your m43 lenses perform as well as comparable lenses work on FF, then the m43 lenses are optically superior. If they were not, the system woud perform less well due to the aberrations being magnified more.

What I don't understand how something this simple and elementary can cause a storm of opposition or disbelief.

Maybe you misunderstood me? I didn't say that FF is better than m43 of big format is better than smaller one, but touched one little bit of optics.

Also, since you only use m43-lenses this has no practical effect on you, but many use mirrorless on adapted lenses where the performance may be less than the user expects based on how the lens performs on the system it was designed for.

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
1

Anders W wrote:

May I remind you that you entered an exchange between me and posters who made claims based on enlargement that there were good reasons for me to question.

All I said then was:

Does anybody have a doubt, that for whatever reason, systems with larger sensors do provide more resolution?

This remains true as of today.

One good way to get FL control is to have a capable zoom (with less lenses in the bag). The m43 system has no meaningful answer to the FF f/4 zooms.

For my needs, the 12-40/2.8 is a meaningful answer. When I need the FF equivalent of f/4 or (or a bit wider) for subject isolation by background blur, I would usually use my 45/1.8 and/or 75/1.8. I prefer that to carrying a 70-200/4 FF zoom.

F/4 needed for subject isolation? Really? Did I isolate the subject well here:

35/4

How about here?

70-200 at f/4

EDIT: DXOmark contradicts your claim that the 20/1.4 is sharper than the Canon 50/1.4 (as PZ does), by far, but you knew that, right?

As to PZ, I already notified you here

http://www.dpreview.com/forums/post/53900103

of the fact that you have apparently overlooked the big sign about non-comparability across platforms posted on their home page.

Well, I did, and I am still well and alive. Better than comparing some voodoo acutance scores.

 Just another Canon shooter's gear list:Just another Canon shooter's gear list
Canon EOS 5D Mark II Canon EF 15mm f/2.8 Fisheye Canon EF 35mm F1.4L USM Canon EF 50mm f/1.2L USM Canon EF 135mm F2L USM +4 more
Anders W Forum Pro • Posts: 21,468
Re: Here is how it actually works
2

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

Anders W wrote:

Truthiness wrote:

knickerhawk wrote:

We're talking about cropped sensors, not cropped images.

It does not matter how you crop the image!

If you need to stretch a 1cm image to 100cm output size, the aberrations of the lens will be more visible than if you stretch a 2cm image to 100cm output size. This is obvious so it is a bit odd how someone gets the motivation to argue it.

Apparently, you overlooked some of the earlier replies in the thread, for example this one:

Apparently you didn't bother to read what I wrote and have wrote before in this thread.

In other words, for two lenses with identical designs but scaled in all relevant dimensions so as to create image circles of different size (e.g., a 50/1.8 for FF scaled downwards so as to make a 25/1.8 for MFT)

You're now talking about apples and oranges.

The point made was the more you need to enlarge an image, the more the aberrations will show, thus the lower the resolution will be.

This of course only applies to the same lens only and that's been the thing I've made an argument about.

What you are now doing is that you're changing the lens. That is beside the point I was making, as the point was about how small sensor stresses the lens more than a larger one. The same lens, not a different one.

So what you now

I've claimed just this all the time. Maybe you just misunderstood?

claim is merely that if a lens made for FF is used with MFT it will perform less well than if it is used with the format for which it was originally made.

In what way is that trivial claim an inherent advantage of the larger format? All the lenses I use with MFT are made for MFT.

If the lenses are equally good, the larger format has an inherit advantage.

No, that's not what you claimed. There was no "if" preceding the claim that the larger format has an inherent (the word is "inherent", not "inherit") advantage. Here's what you originally said once more:

"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."

So once again: What exactly is that inherent advantage if you can take a lens designed for the larger format and just scale it downwards to achieve the same aberration-limited resolution per image diagonal?

This is what I claimed. If you scale the lenses perfectly down, you improve the lens as you reduce the aberrations.

The simple statement I made means that if your m43 lenses perform as well as comparable lenses work on FF, then the m43 lenses are optically superior. If they were not, the system woud perform less well due to the aberrations being magnified more.

What I don't understand how something this simple and elementary can cause a storm of opposition or disbelief.

Maybe you misunderstood me? I didn't say that FF is better than m43 of big format is better than smaller one, but touched one little bit of optics.

Also, since you only use m43-lenses this has no practical effect on you, but many use mirrorless on adapted lenses where the performance may be less than the user expects based on how the lens performs on the system it was designed for.

 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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