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What is the sharpest 24mm lens you know of?
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PostPosted: Wed Jun 29, 2022 7:43 pm    Post subject: Reply with quote
I'm tempted to say a certain lens is fantastic, just so the Swiss troll will go away and find a copy and waste his time shooting pointless extreme corner shots with it just to prove me wrong.


PostPosted: Wed Jun 29, 2022 8:16 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
I'm tempted to say a certain lens is fantastic, just so the Swiss troll will go away and find a copy and waste his time shooting pointless extreme corner shots with it just to prove me wrong.


The best way to prove you're right and he's wrong is to take pictures (using an FF camera, of course) with the lenses on your list of "excellent" lenses, and then show that the Yashica is the best of them all. Why don't you do it?


PostPosted: Wed Jun 29, 2022 8:21 pm    Post subject: Reply with quote
YOU are telling me to go take pictures?

That has to be the height of hipocrisy.

How about you go take some pictures and post them...

Which you NEVER do....

although you often lie and claim otherwise


PostPosted: Wed Jun 29, 2022 8:33 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
YOU are telling me to go take pictures?


Yeah, if you just keep mumbling, I don't see how you'll prove your point.


PostPosted: Wed Jun 29, 2022 8:45 pm    Post subject: Reply with quote
I have nothing to prove to a liar and troll like you.


PostPosted: Wed Jun 29, 2022 9:04 pm    Post subject: Reply with quote
I don't think you understand where the problem is. You don't need to prove to ME that Yashica is the best lens on your list. You need to prove it to the OTHER people you showed your list of "excellent" lenses.


PostPosted: Wed Jun 29, 2022 10:12 pm    Post subject: Reply with quote
The problem is your continual trolling. If you went away or just STFU, everything would be much better.


PostPosted: Wed Jun 29, 2022 10:16 pm    Post subject: Reply with quote
stevemark wrote:
D1N0 wrote:
stevemark wrote:
P FF tests, these were done using the 43 MP FF sony A7RII. The 50 MP class sensors are much more demanding on vintage lenses; thus 24 MP images would look quite a bit better!
I don't think I agree with that. ...
If you insist on 1:1 cropping you will end up with larger crops on a 42mp sensor than on a 24mp sensor.

Of course! That's the idea behind getting a sensor with higher MP, after all ...


So you are comparing two different magnification levels as if they were the same.[/quote]
Sure ... what's the problem??

S[/quote]

The problem is they are not the same. IQ is not worse on 46mp, since corner resolution is much lower than that. You are able to show worse 1:1 crops, but that is immaterial. Show the same area using a 24mp and a 50mp sensor, all will see is higher resolution blur, since resolving capability in the corners is maybe 8mp (I am being optimistic :p ).


PostPosted: Thu Jun 30, 2022 9:04 am    Post subject: Reply with quote
stevemark wrote:
Unlike my usual 24 MP FF tests, these were done using the 43 MP FF sony A7RII. The 50 MP class sensors are much more demanding on vintage lenses; thus 24 MP images would look quite a bit better!


sDN10 wrote:
I don't think I agree with that. On either sensor the corners will not be out-resolved. If you insist on 1:1 cropping you will end up with larger crops on a 42mp sensor than on a 24mp sensor. So you are comparing two different magnification levels as if they were the same.


stevemark wrote:
Of course! That's the idea behind getting a sensor with higher MP, after all ...

DN10 wrote:
So you are comparing two different magnification levels as if they were the same.

Sure ... what's the problem??


DN10 wrote:
The problem is they are not the same. IQ is not worse on 46mp, since corner resolution is much lower than that. You are able to show worse 1:1 crops, but that is immaterial. Show the same area using a 24mp and a 50mp sensor, all will see is higher resolution blur, since resolving capability in the corners is maybe 8mp (I am being optimistic :p ).


I suspect this is a red herring; I can see the argument from both your perspectives.

I think Stephan's statement that 50 MP class sensors are much more demanding on vintage lenses is simply a bit unfortunate in its phrasing; I would argue that sensors don't really demand anything from a lens (other than a minimum exit pupil distance perhaps).

Ultimately it is the intended use of the final image that places minimum demands on both the lens resolving power and the sensor resolution. 50 MP class sensors simply enable the resolving power of a lens to be inspected at higher resolution.

Obviously, in order to reliably determine the resolving power of a lens using a digital sensor, the sensor resolution (incl. allowance for any AA filter in the filter stack) will need to exceed the lens resolving power by some significant margin in order to get a clean convolution of the sensor's and lens' "point spread functions" free of any aliasing artefacts. (really not sure if "point spread functions" is the most appropriate terminology here, but hopefully you get my drift). Ideally the sensor resolution would need to exceed by some margin the theoretical diffraction limit of the optics, just in case the lens resolution power turns out to be diffraction-limited already at maximum aperture.

Thus, a much higher sensor resolution (e.g. 50 MP) will allow the lens' resolution power to be inspected more accurately, even when in practice on such a high resolution sensor the resulting image quality may look hardly any different for a lens with modest resolution power.

That's my view, but I may have misunderstood the argument Wink


PostPosted: Thu Jun 30, 2022 2:05 pm    Post subject: Reply with quote
RokkorDoctor wrote:
stevemark wrote:
Unlike my usual 24 MP FF tests, these were done using the 43 MP FF sony A7RII. The 50 MP class sensors are much more demanding on vintage lenses; thus 24 MP images would look quite a bit better!


sDN10 wrote:
I don't think I agree with that. On either sensor the corners will not be out-resolved. If you insist on 1:1 cropping you will end up with larger crops on a 42mp sensor than on a 24mp sensor. So you are comparing two different magnification levels as if they were the same.


stevemark wrote:
Of course! That's the idea behind getting a sensor with higher MP, after all ...

DN10 wrote:
So you are comparing two different magnification levels as if they were the same.

Sure ... what's the problem??


DN10 wrote:
The problem is they are not the same. IQ is not worse on 46mp, since corner resolution is much lower than that. You are able to show worse 1:1 crops, but that is immaterial. Show the same area using a 24mp and a 50mp sensor, all will see is higher resolution blur, since resolving capability in the corners is maybe 8mp (I am being optimistic :p ).


I suspect this is a red herring; I can see the argument from both your perspectives.

I think Stephan's statement that 50 MP class sensors are much more demanding on vintage lenses is simply a bit unfortunate in its phrasing; I would argue that sensors don't really demand anything from a lens (other than a minimum exit pupil distance perhaps).

Ultimately it is the intended use of the final image that places minimum demands on both the lens resolving power and the sensor resolution. 50 MP class sensors simply enable the resolving power of a lens to be inspected at higher resolution.

Obviously, in order to reliably determine the resolving power of a lens using a digital sensor, the sensor resolution (incl. allowance for any AA filter in the filter stack) will need to exceed the lens resolving power by some significant margin in order to get a clean convolution of the sensor's and lens' "point spread functions" free of any aliasing artefacts. (really not sure if "point spread functions" is the most appropriate terminology here, but hopefully you get my drift). Ideally the sensor resolution would need to exceed by some margin the theoretical diffraction limit of the optics, just in case the lens resolution power turns out to be diffraction-limited already at maximum aperture.

Thus, a much higher sensor resolution (e.g. 50 MP) will allow the lens' resolution power to be inspected more accurately, even when in practice on such a high resolution sensor the resulting image quality may look hardly any different for a lens with modest resolution power.

That's my view, but I may have misunderstood the argument Wink


I can't imagine a better explanation Like Dog


PostPosted: Fri Jul 01, 2022 1:27 am    Post subject: Reply with quote
Statements such as "this lens outperforms the sensor", or vice versa, are often used in discussions about the performance of a lens against the resolution of a sensor. However, these comparisons are more complicated than they seem at first glance.

Firstly, the performance of a lens varies according to the zone of the frame. The performance in the center is generally considerably better than in the corners. Second, the performance of a lens varies greatly with the aperture used.

It is entirely possible, therefore, that the sensor outperforms the lens at the edges and corners, but at the center it is the opposite. So when you want the best overall image definition, in general, the higher the sensor resolution, the better.

However, the most important question is how to measure the "performance" of a sensor or a lens. The sensor, in general, can be characterized simply by its resolution, but characterizing a lens is much more complicated.

A unified way to measure the performance of a lens AND a sensor is through the so-called Modulation Transfer Function, MTF. However, the behavior of the MTF of a sensor is quite different from a typical lens. The MTF of a 24 MP full-frame sensor drops to zero at a spatial frequency of 82 lp/mm, while a pedestrian lens, such as the Helios 44M-4, in the center of the field has a non-zero MTF (~10%) for frequencies just above of 200 lp/mm, even for the diaphragm wide open!

http://forum.mflenses.com/the-amazingly-high-resolution-of-a-helios-44m-4-t65636,highlight,+amazingly.html


PostPosted: Fri Jul 01, 2022 9:19 am    Post subject: Reply with quote
Gerald wrote:
However, the most important question is how to measure the "performance" of a sensor or a lens. The sensor, in general, can be characterized simply by its resolution, but characterizing a lens is much more complicated.

A unified way to measure the performance of a lens AND a sensor is through the so-called Modulation Transfer Function, MTF. However, the behavior of the MTF of a sensor is quite different from a typical lens. The MTF of a 24 MP full-frame sensor drops to zero at a spatial frequency of 82 lp/mm, while a pedestrian lens, such as the Helios 44M-4, in the center of the field has a non-zero MTF (~10%) for frequencies just above of 200 lp/mm, even for the diaphragm wide open!


I can see the point of quoting the MTF's for a lens; it is far from a perfect performance measure, but with the continuous nature of light as observed in a conventional optics set-up (thus focusing on the wave-behaviour of light and ignoring the quantum-behaviour), it is a reasonably well-behaved metric for conventional optics, and contains practical information for a photographer.

I am not so sure MTF's are all that good/useful a measure for sensor performance for your everyday photographer. The discrete nature of the photo-sites (and the particular configuration of colour filters) causes all sorts of issues if you try and determine the MTF of a sensor near the lp/mm close to the spacial frequency of the photo-sites. It gets even worse in absence of an anti-aliasing filter.

Thus for digital camera sensors the MTF metric becomes very ill-behaved as a metric (or more complex might be a better word Wink ) , precisely in the resolution range where the MTF is anticipated to show something useful about the resolving power of the test subject (sensor).

However, I suspect that very extensive/elaborate measurement of the MTF(s) at a range of different tangential microscopic displacements could tell you something about the degree to which the sensor design is liable to aliasing effects. I suspect that the likely very complex MTF(s) of a sensor are therefore more useful as an R&D measure for the sensor developers, than they are for your average photographer...


PostPosted: Fri Jul 01, 2022 10:45 am    Post subject: Reply with quote
For the average photographer, MTF is meaningless, all that matters is if the lens is sharp enough to satisfy their tastes.

Some people talk and talk and talk and never take any pictures, hence they are more troll than photographer and don't understand how the average photographer thinks.


PostPosted: Fri Jul 01, 2022 11:41 am    Post subject: Reply with quote
MTF becomes more sensible if it would be done on the whole process to an output format, so including RAW conversion, upsampling and sharpening routines, 4or8K output, print size and print/paper quality, MTF measurements on prints is hardly done. In general the gear we use delivers way more than usually the output quality/sizes demand. A rough estimate for inkjet prints is that with 450PPI input (at the size of the print) to the printer driver is the best that can be laid down on inkjet papers, more does not harm but does not add. Preferably 450 quality pixels though. As long as the total chain is not properly MTF measured the MTF of the two first steps in the process is not worth much. Whether our eyes at a certain distance can not see the actual resolution of a certain size print etc is something I am not much concerned about. We do not keep that distance in mind when watching but scan the image, go forward and backwards, act different on wide angle prints than on tele ones, and in total build up an impression that way. Call it Gestalt or whatever. Paper textures are often not visible either at viewing distances yet we consider them part of the image as well .


PostPosted: Fri Jul 01, 2022 11:55 am    Post subject: Reply with quote
RokkorDoctor wrote:
I am not so sure MTF's are all that good/useful a measure for sensor performance for your everyday photographer. The discrete nature of the photo-sites (and the particular configuration of colour filters) causes all sorts of issues if you try and determine the MTF of a sensor near the lp/mm close to the spacial frequency of the photo-sites. It gets even worse in absence of an anti-aliasing filter.

In fact, since RCA's development of the picture tube-based TV shortly after World War II, MTF is routinely used by engineers working with image sensors. Both an image tube (iconoscope, orthicon, vidicon, etc.) and solid state sensors (CCD, MOS) are basically spatial samplers of the image projected by the lens. Sampling theory is solidly established and there is no fundamental difficulty in measuring the MTF of an image sensor.

As an example, the figure below shows the MTF of a CCD sensor used in Olympus microscopes. By the way, 6.7 micrometer is slightly greater than the 6 micrometer pixel pitch of a 24MP full-frame sensor.


https://www.olympus-lifescience.com/en/microscope-resource/primer/digitalimaging/digitalimagingdetectors/

Last edited by Gerald on Fri Jul 01, 2022 1:29 pm; edited 1 time in total


PostPosted: Fri Jul 01, 2022 12:48 pm    Post subject: Reply with quote
Ernst Dinkla wrote:
MTF becomes more sensible if it would be done on the whole process to an output format, so including RAW conversion, upsampling and sharpening routines, 4or8K output, print size and print/paper quality, MTF measurements on prints is hardly done.

Undoubtedly, if you know the MTF of each individual element in the chain of an optical-electronic system, you can calculate the global MTF of the system. However, this fact does not diminish the importance of measuring the MTF of an element simply to characterize it properly, regardless of where it will be used. This explains, for example, why lens manufacturers measure MTF of their lenses, even without knowing exactly how these lenses will be used in practice.


PostPosted: Fri Jul 01, 2022 1:41 pm    Post subject: Reply with quote


PostPosted: Fri Jul 01, 2022 2:25 pm    Post subject: Reply with quote
Henri didn't have AF or focus peaking or live view magnification so he had an excuse Wink Nowadays not so much :p


PostPosted: Fri Jul 01, 2022 4:16 pm    Post subject: Reply with quote
The edge test by stevemark is remarkable. Thx for the hard work.
It shows that at f3 the minolta md iii lena is the sharpest 24 mm lens. The other ines are blurry but your samole is on full frame or am i mistaken?

Gerald MTF measurement is nice but can we really measure a lens if every old LenS has more or less a different sharpness due to tolerances at production time and usage. ? Some are even slightly decentered over the time. ! Sry but this is a bit strange to mention it here in this detailed way.

However d1n0 is also right nowadays a certain level of sharpness is important and to be honest i would sell a blurry lens with too heavy CA's directly.

Which 24 mm is then rather cheap and good?


PostPosted: Fri Jul 01, 2022 4:49 pm    Post subject: Reply with quote
D1N0 wrote:
Henri didn't have AF or focus peaking or live view magnification so he had an excuse Wink Nowadays not so much :p


I think he was right though in that sharpness isn't the be all and end all of photography and if an image is strong enough in other regards, sharpness or a lack thereof can be overlooked.


PostPosted: Fri Jul 01, 2022 5:13 pm    Post subject: Reply with quote
bluedxca93 wrote:
Gerald MTF measurement is nice but can we really measure a lens if every old LenS has more or less a different sharpness due to tolerances at production time and usage. ? Some are even slightly decentered over the time. ! Sry but this is a bit strange to mention it here in this detailed way.

Indeed, lens performance varies a bit from copy to copy, however the variation is not very big (about 20% of the MTF value) for good lenses. One use of the MTF measurement is precisely to separate the good lenses from the "lemons". I used the mtf_mapper program to measure the MTF50 of all my lenses, so now I know exactly how they perform.


PostPosted: Fri Jul 01, 2022 6:33 pm    Post subject: Reply with quote
Gerald wrote:
I used the mtf_mapper program to measure the MTF50 of all my lenses, so now I know exactly how they perform.


Prove it.

Post some images, otherwise, why should anyone believe a word you say?

Especially as lately you have been caught out telling a LOT of deliberate falsehoods.

Methinks you might be a false expert and full of it....


PostPosted: Fri Jul 01, 2022 6:41 pm    Post subject: Reply with quote
Gerald just tell us one or more of your lenses that are in or near the range of 24 mm and have a good mtf50. Now that you mentioned it we are very interested. Im just curious about. Also why not show us in a seperate thread hiw to use the mtf mapper.I am not against all of your opinions but taking the mtf chart of a lens would take a considerable amount of time. Even if you only need 1 hour for four lenses that is time intensive if you like testing lenses. Most users take photos and compare them. The freaky ones take pictures of red brick walls to test sharpness, vignetting and so on.


PostPosted: Fri Jul 01, 2022 8:36 pm    Post subject: Reply with quote
Gerald wrote:
RokkorDoctor wrote:
I am not so sure MTF's are all that good/useful a measure for sensor performance for your everyday photographer. The discrete nature of the photo-sites (and the particular configuration of colour filters) causes all sorts of issues if you try and determine the MTF of a sensor near the lp/mm close to the spacial frequency of the photo-sites. It gets even worse in absence of an anti-aliasing filter.

In fact, since RCA's development of the picture tube-based TV shortly after World War II, MTF is routinely used by engineers working with image sensors. Both an image tube (iconoscope, orthicon, vidicon, etc.) and solid state sensors (CCD, MOS) are basically spatial samplers of the image projected by the lens. Sampling theory is solidly established and there is no fundamental difficulty in measuring the MTF of an image sensor.


I didn't suggest it isn't used or shouldn't be used for image sensors, but rather that the MTF for image sensors requires great care in its interpretation. Something engineers are aware of but the average photographer will likely not be.

It is certainly possible to measure the MTF of an image sensor, but for a sensor without an AA filter, near the Nyquist frequency (or slightly beyond) the resulting MTF values become difficult to interpret. On a sensor without an AA filter, a little beyond the Nyquist frequency the MTF reads non-zero, but what it is measuring is a heavily aliased signal, hardly a good indicator for sensor resolving power. The colour filter pattern (e.g. bayer) + associated processing makes the issue even more complicated, again especially in the absence of an AA filter.

http://www.normankoren.com/Tutorials/MTF2.html

Bottom line is that optical engineers will be aware of these issues and interpret the MTF measurement with due caution, but an average photographer will look at an MTF value of say 0.3 of an aliased sensor output, and mistakenly think the sensor can still resolve some relevant detail there.

Gerald wrote:
As an example, the figure below shows the MTF of a CCD sensor used in Olympus microscopes. By the way, 6.7 micrometer is slightly greater than the 6 micrometer pixel pitch of a 24MP full-frame sensor.


https://www.olympus-lifescience.com/en/microscope-resource/primer/digitalimaging/digitalimagingdetectors/


The Olympus article doesn't make any mention of it, but that graph to me looks like the sensor has an aggressive AA filter, and they are probably processing multiple photo-sites samples into a lower number of output pixels to ensure sufficient quality resolution (which is something they do mention in their article). Of course then the MTF becomes well-behaved, but drops to zero faster than you at face value would theoretically expect from a 6.7 micrometer pixel size sensor.


PostPosted: Fri Jul 01, 2022 8:56 pm    Post subject: Reply with quote
bluedxca93 wrote:

Gerald just tell us one or more of your lenses that are in or near the range of 24 mm and have a good mtf50. Now that you mentioned it we are very interested. Im just curious about. Also why not show us in a seperate thread hiw to use the mtf mapper.I am not against all of your opinions but taking the mtf chart of a lens would take a considerable amount of time. Even if you only need 1 hour for four lenses that is time intensive if you like testing lenses. Most users take photos and compare them. The freaky ones take pictures of red brick walls to test sharpness, vignetting and so on.


My first lens after the normal lens that came with a Praktica LTL-3 was a Pentacon 29mm F2.8. The 28/29/30mm lenses are very interesting because they are wide-angle with good coverage, but without their wide-angle character being too prominent for the viewer. This perhaps explains why in the Zeiss Otus lineup there is only one wide-angle lens, precisely the 28mm.

After the Pentacon 29mm I went straight to a 20mm super wide angle. You know, a 24mm (or 25mm) lens has an intermediate coverage between 28mm and 20mm. There's not much gain in going from 28mm to 24mm in practice. When the composition calls for a 24mm lens, I simply use my 20mm lens and crop the result in PP.

There are those who like the 24mm focal length, which has become standard in the professional 24-70mm F2.8 zoom lenses and APS-C format kit lenses, which start at 18mm, equivalent to a 24mm for FF format. .

About the mtf_mapper program, it is free and relatively easy to use. I use an older version, so I believe there is a more up-to-date version today, but the version I use works well for my purposes. The most critical in using mtf_mapper is the chart with the black rectangles:



This chart needs to be at least 1 meter wide, and the squares need to have very sharp edges, but you can print the chart piece by piece and stitch it together later.
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