Relationship between Sensor Size and diffraction

[quadrox]

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.
2. All else being equal, smaller sensors have more DOF at a given f-stop.

My main question is now, will the two effects above cancel out for equivalent photos? That is:

Will equivalent photos taken at the same resolution, with the same FOV and DOF have different amounts of diffraction?

My intuition says that they will have the same amount of diffraction. If that is correct, I see one alternative aspect where larger formats may yield higher resolution: Lens sharpness.

Once more, it is my understanding that:

1. Lenses for smaller sensors are easier to make sharper than lenses for larger sensors...
2. ... But because larger sensors (having same resolution) will have larger pixels, this effect is again reduced

So therefore my second question is:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

 

[Detail Man]

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.
2. All else being equal, smaller sensors have more DOF at a given f-stop.

Please provide a specific list of what is included in "all else" that is equal. Please within that list clarify whether that includes number of Photosites, Photodetector Fill Factor and Shape, AA Filter "strength", as well as the Angle of View of the camera-lens systems being compared.

My main question is now, will the two effects above cancel out for equivalent photos? That is:

Will equivalent photos taken at the same resolution, with the same FOV and DOF have different amounts of diffraction?

My intuition says that they will have the same amount of diffraction. If that is correct, I see one alternative aspect where larger formats may yield higher resolution: Lens sharpness.

Once more, it is my understanding that:

1. Lenses for smaller sensors are easier to make sharper than lenses for larger sensors...
2. ... But because larger sensors (having same resolution) will have larger pixels, this effect is again reduced

So therefore my second question is:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

 

[quadrox]

Detail Man wrote:

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.
2. All else being equal, smaller sensors have more DOF at a given f-stop.

Please provide a specific list of what is included in "all else" that is equal. Please within that list clarify whether that includes number of Photosites, Photodetector Fill Factor and Shape, AA Filter "strength", as well as the Angle of View of the camera-lens systems being compared.

I had assumed that my intent was quite clear from the way I phrased the question, but here comes the clarification

• Sensor technology itself is identical - same same QE, same number of photosites etc. - the larger sensor just uses larger versions of the photosite/pixels to arrive at the same resolution.
• AA filter would of course would be equivalent, not identical - or to make it easier, assume a foveon sensor and no AA filter.
• Sensor format would be the same of course.
• Lenses would be equivalent lenses - in real life this is near impossible, but for a theoretical discussion this should be allowed.

Basically, I want everything to be as equivalent as possible, only one sensor is larger and therefore has larger pixels. In that case, will there be a difference in diffraction?

Or put another way, if we had a film/sensor medium with infinite resolution and lenses with perfect sharpness, would a camera using a larger format show less, the same, or more diffraction effects?

 

[Donald B]

not having ever understood diffraction, can someone post some photos showing the effect.

cheers don

 

[Detail Man]

quadrox wrote:

Detail Man wrote:

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.

Define how "suffering from diffraction" would be assessed. Via composite spatial frequency response ?

1. All else being equal, smaller sensors have more DOF at a given f-stop.

Please provide a specific list of what is included in "all else" that is equal. Please within that list clarify whether that includes number of Photosites, Photodetector Fill Factor and Shape, AA Filter "strength", as well as the Angle of View of the camera-lens systems being compared.

I had assumed that my intent was quite clear from the way I phrased the question, but here comes the clarification

• Sensor technology itself is identical - same same QE, same number of photosites etc. - the larger sensor just uses larger versions of the photosite/pixels to arrive at the same resolution.

Your use of the term "resolution" above is referring to pixel-resolution per linear dimension, then.

• AA filter would of course would be equivalent, not identical - or to make it easier, assume a foveon sensor and no AA filter.

"Equivalent" in terms of the beam-splitting offset relative to the photosite-pitch dimension, then.

• Sensor format would be the same of course.

If sensor format would be the same, then one could not have "smaller" and "larger" active-areas.

• Lenses would be equivalent lenses - in real life this is near impossible, but for a theoretical discussion this should be allowed.

By that you mean that the ratio of the Focal Lengths as well as the F-Numbers would be equal to the ratio of the (linear) dimensions of the active-areas of the photosites. Same Angle of View, then ?

Basically, I want everything to be as equivalent as possible, only one sensor is larger and therefore has larger pixels. In that case, will there be a difference in diffraction?

 

[quadrox]

Detail Man wrote:

quadrox wrote:

Detail Man wrote:

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.

Define how "suffering from diffraction" would be assessed. Via composite spatial frequency response ?

Well, something simple as MTF 50 would suffice I guess. Take a photo of a canvas with a sufficient number of line pairs with both sensors and see how many you can get on each image. I am open to other suggestions though.

Your use of the term "resolution" above is referring to pixel-resolution per linear dimension, then.

Yes!

• AA filter would of course would be equivalent, not identical - or to make it easier, assume a foveon sensor and no AA filter.

"Equivalent" in terms of the beam-splitting offset relative to the photosite-pitch dimension, then.

Exactly!

• Sensor format would be the same of course.

If sensor format would be the same, then one could not have "smaller" and "larger" active-areas.

Ah, excuse my poor turn of phrase there - I meant the ratio of sensor side lengths.

• Lenses would be equivalent lenses - in real life this is near impossible, but for a theoretical discussion this should be allowed.

By that you mean that the ratio of the Focal Lengths as well as the F-Numbers would be equal to the ratio of the (linear) dimensions of the active-areas of the photosites. Same Angle of View, then ?

Exactly, same AOV, same DOF.

 

[Mark S Abeln]

quadrox wrote:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

Diffraction occurs along edges. A big lens with a big opening will have less diffraction than a small lens with a small opening.

It is a simple matter of geometry. A lens with a diameter d will have a surface area of π(d/2)^2, while its circumference (which is the size of the edge) is πd. The relative amount of diffraction of a lens is therefore the circumference divided by the area, which is 4/d. The relative amount of diffraction is therefore inversely proportional to the lens diameter: a small lens will have more diffraction, while a large lens will have less.

A big sensor of a given f/stop will have a larger lens for any given angle of view compared to a smaller sensor, therefore the big sensors will typically have less diffraction and potentially greater sharpness.

--

http://therefractedlight.blogspot.com

 

[quadrox]

Donald B wrote:

not having ever understood diffraction, can someone post some photos showing the effect.

Diffraction is something that is usually very difficult to discern from other effects without pixel peeping and photographing test charts. A good example can be found here:

http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

Much more important (if it is important at all) is to understand the theory behind it. Some basic understanding can be found here, though I have previously found a much better explanation somewhere else:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

 

[Detail Man]

quadrox wrote:

Detail Man wrote:

quadrox wrote:

Detail Man wrote:

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.

The F-Stop cannot be the same according to your clarified framing of the questions (below).

If the ratio of the F-Stops is equal to the reciprocal of the Crop Factors of the image-sensors compared, and the size of the Photosites (assuming the same Fill Factor and photodector shape and AA Filter strength) are equal to the reciprocal of the Crop Factors of the image-sensors compared, then the interaction between the spatial frequency response due to lens-system diffraction and the spatial frequency response due to the Photosite size (assuming the same Fill Factor and photodector shape and AA Filter strength) are the same.

So, the statement above (as you have upon request for clarification defined it) would be incorrect.

1. All else being equal, smaller sensors have more DOF at a given f-stop.

The F-Stop cannot be the same according to your clarified framing of the questions (below).

In a situation where the F-Stops and Focal Lengths are the same, the DOF is directly proportional to the ratio of the (linear) image-sensor dimensions. The inverse of your statement.

Define how "suffering from diffraction" would be assessed. Via composite spatial frequency response ?

Well, something simple as MTF 50 would suffice I guess. I am open to suggestions though.

MTF 50 would be affected, by why not consider the entire modulation transfer function (MTF) ?

Your use of the term "resolution" above is referring to pixel-resolution per linear dimension, then.

Yes!

• AA filter would of course would be equivalent, not identical - or to make it easier, assume a foveon sensor and no AA filter.

"Equivalent" in terms of the beam-splitting offset relative to the photosite-pitch dimension, then.

Exactly!

• Sensor format would be the same of course.

If sensor format would be the same, then one could not have "smaller" and "larger" active-areas.

Ah, excuse my poor turn of phrase there - I meant the ratio of sensor side lengths.

• Lenses would be equivalent lenses - in real life this is near impossible, but for a theoretical discussion this should be allowed.

By that you mean that the ratio of the Focal Lengths as well as the F-Numbers would be equal to the ratio of the (linear) dimensions of the active-areas of the photosites. Same Angle of View, then ?

Exactly, same AOV, same DOF.

I think that what is going on is simply that it is commonly (though not invariably) the case that larger sized image-sensors have a larger number of photosites than smaller sized image-sensors, which results in a higher resolution per image-height or image-width.

In the case you propose (of an equal number of photosites) the assertion would not be true - although it may be that one or another lens-systems used with one or another format might (due to differences in lens-system aberrations, as opposed to diffraction) have a higher magnitude measurable spatial frequency response as a function of spatial frequency.

Note, however, that the limitations on the spatial frequency response of a lens are absolute:

MTF of lens-system due to Diffraction: (2/pi) * ( ArcCosine(f) - (f) * Sqrt ( 1 - (f)^2 ) )

where f is the dimensionless product of Spatial Frequency multiplied by Wavelength * F-Number.

... where "extinction" occurs at a spatial frequency equal to the reciprocal of the product of Wavelength multiplied by F-Number, and the effects of lens-system optical aberrations will only reduce the magnitiude of the MTF response below that limiting spatial frequency response.

You might find this recent thread about composite MTF interesting and perhaps informative:

http://www.dpreview.com/forums/thread/3475094

 

[Detail Man]

Mark Scott Abeln wrote:

quadrox wrote:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

Diffraction occurs along edges. A big lens with a big opening will have less diffraction than a small lens with a small opening.

It is a simple matter of geometry. A lens with a diameter d will have a surface area of π(d/2)^2, while its circumference (which is the size of the edge) is πd. The relative amount of diffraction of a lens is therefore the circumference divided by the area, which is 4/d. The relative amount of diffraction is therefore inversely proportional to the lens diameter: a small lens will have more diffraction, while a large lens will have less.

A big sensor of a given f/stop will have a larger lens for any given angle of view compared to a smaller sensor, therefore the big sensors will typically have less diffraction and potentially greater sharpness.

I think that all that matters where it comes to diffraction is the F-Ratio - the lens-system Focal Length divided by the diameter of the entrance-pupil (the size that the mechanical aperture appears to be when looking into the front element of the lens-system from the outside) multiplied by the Wavelength. I don't think that the aperture formed by the lens-system front element matters.

 

[Joseph S Wisniewski]

Mark Scott Abeln wrote:

quadrox wrote:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

Diffraction occurs along edges.

No, it doesn't. Diffraction is a function of wave interfearance and information theory, relating to the size of the lens. You have to ray trace the entire lens to analyze it. An apodized lens, one with a radial gradient neutral density edge still suffers diffraction, and actually a bit more than one with the same area and a hard edge.

A big lens with a big opening will have less diffraction than a small lens with a small opening.

It is a simple matter of geometry.

No, it's a complex matter of we equations. I don't know where you got the following analysis, but it's totally wrong.

A lens with a diameter d will have a surface area of π(d/2)^2, while its circumference (which is the size of the edge) is πd. The relative amount of diffraction of a lens is therefore the circumference divided by the area, which is 4/d. The relative amount of diffraction is therefore inversely proportional to the lens diameter: a small lens will have more diffraction, while a large lens will have less.

A big sensor of a given f/stop will have a larger lens for any given angle of view compared to a smaller sensor, therefore the big sensors will typically have less diffraction and potentially greater sharpness.

 

[Joseph S Wisniewski]

quadrox wrote:

I have never quite understood how larger formats are supposed to allow for higher resolution,

They "allow for higher resolution" by permitting larger lenses for a given angle of view. That is literally the only parameter that matters in image formation.

but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.

True, but totally irrelevant.

1. All else being equal, smaller sensors have more DOF at a given f-stop.

Again, true, but irrelevant.

My main question is now, will the two effects above cancel out for equivalent photos? That is:

Will equivalent photos taken at the same resolution, with the same FOV and DOF have different amounts of diffraction?

No. Taken at the same resolution, with the same DOF, diffraction will also be identical. I.e. 25mm f1.4 on micro four thirds and 50mm f2.8 on FF both are covering roughly a 46 degree diagonal through a 17.9mm aperture, resulting in essentially identical DOF and diffraction.

My intuition says that they will have the same amount of diffraction. If that is correct, I see one alternative aspect where larger formats may yield higher resolution: Lens sharpness.

Correct.

Once more, it is my understanding that:

1. Lenses for smaller sensors are easier to make sharper than lenses for larger sensors...

No. For a given aperture, the smaller lens is easier to make. For a given resolution (diffraction-DOF pairing) the lens for the larger camera is much easier to make.

Like my example, it's a lot easier to make a small, inexpensive 4 or 5 element 50mm f2.8 for FF with near distortion free performance, high contrast, and high resolution across the entire frame due to an absence of curvature of field.

A 25mm f1.4 for four thirds is insane. The Panasonic-Leica 25mm f1.4 is 9 elements, twice the cost of a 45mm or 50mm f2.8 FF lens, and because it's f1.4 it needs twice the precision in assembly as the f2.8 FF lens. You then multiply that by (9/4)^2 to get the precision required for the increased number of elements. Put it all together, and the lens for the smaller sensor literally needs to be built to 10x the precision.

1. ... But because larger sensors (having same resolution) will have larger pixels, this effect is again reduced

So therefore my second question is:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

Yes. Their designs are simpler and therefore, their performance is higher. For a given image (identical DOF and diffraction) building "diffraction limited" lenses, lenses that perform to the theoretical maximum resolution for a particular aperture diameter, is much easier in larger formats. The large format simplifies the lens design, at the expense of the camera design (louder, slower shutters and mirrors, for camera that still have mirrors, larger lens mounts, etc).

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

Hope this helps.

 

[Dr JLW]

The simple explanation is that diffraction is spreading out of focused light as a consequence of its wave character.

In practice the size of a diffraction focus spot is about equal to 1.5 times the f/number ( it runs from about 1.2 to 2 depending on whether the scene is red or blue but 1.5 is reasonable. This at f/4 your diffraction spot is going to be at least 6 microns in diameter. It may be larger due to lens aberrations and or camera shake but its is never going to be smaller. Now suppose you have a 1/2" focal plane that is 6.4 by 4.8mm. If it has 12M Square pixels it has 4,000 pixels over 6.4mm. That is about 1.5 microns per pixel. A group of four pixels is ideal for the spot size so at f/4 your diffraction spot is about 6 microns and the optimal spot is 3 microns so the small focal plane is diffraction limited, although it still could do worse, because of poor lens set up design or camera shake.

Now and APS C pixels is about 16 by 24 mm. It it too has 12M pixels, it has 4,000 pixels spread over 24 mm or about 6 microns per pixel. All f/4 lenses regardless of size that is focal length produce the same 6 micron spot size. Our four pixel group is 24 microns in diameter so at F/4 diffraction is not a the limit of resolution. The lens could still be bad and there could be camera shake of air disturbance but diffraction is not a problem about below f/12 to f/16.

The theory of all of this is very deep as is sampling theory and lens design but if you understand that the diffraction spot size goes as the f/number you have a pretty good idea what is going on.

This is a reason why you should consider using a polarizing filter for shooting with small focal plane cameras in daylight. It enables you to keep the lens between f/4 and f/5.6 rather than f/8 where diffraction will really eat into resolution. Since there is a lot of light the shutter speed is high so there is not much camera shake and a polarizer or ND filter will get you sharper pictures.

 

[olliess]

Joseph S Wisniewski wrote:

Mark Scott Abeln wrote:

It is a simple matter of geometry.

No, it's a complex matter of we equations.

Was that meant to say "wave" equations? or something else?

 

[quadrox]

Joseph S Wisniewski wrote:

Will equivalent photos taken at the same resolution, with the same FOV and DOF have different amounts of diffraction?

No. Taken at the same resolution, with the same DOF, diffraction will also be identical. I.e. 25mm f1.4 on micro four thirds and 50mm f2.8 on FF both are covering roughly a 46 degree diagonal through a 17.9mm aperture, resulting in essentially identical DOF and diffraction.

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

Yes. Their designs are simpler and therefore, their performance is higher. For a given image (identical DOF and diffraction) building "diffraction limited" lenses, lenses that perform to the theoretical maximum resolution for a particular aperture diameter, is much easier in larger formats. The large format simplifies the lens design, at the expense of the camera design (louder, slower shutters and mirrors, for camera that still have mirrors, larger lens mounts, etc).

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

Hope this helps.

Thank you for a clear and concise answer to my question(s) - It is very much appreciated.

In the end that means that medium format and large format only hold an advantage as long as DSLR lenses are not diffraction limited. In the long run it would seem probable that medium/large format would become irrelevant - depending on exactly how much current sensors and lenses can be improved.

 

[olliess]

quadrox wrote:

In the end that means that medium format and large format only hold an advantage as long as DSLR lenses are not diffraction limited.

I think it's correct to say that we're getting to the point where DSLRs significantly affected by diffraction, and may even be said to be diffraction-limited at some apertures.

 

[bobn2]

Joseph S Wisniewski wrote:

Once more, it is my understanding that:

1. Lenses for smaller sensors are easier to make sharper than lenses for larger sensors...

No. For a given aperture, the smaller lens is easier to make. For a given resolution (diffraction-DOF pairing) the lens for the larger camera is much easier to make.

Like my example, it's a lot easier to make a small, inexpensive 4 or 5 element 50mm f2.8 for FF with near distortion free performance, high contrast, and high resolution across the entire frame due to an absence of curvature of field.

A 25mm f1.4 for four thirds is insane. The Panasonic-Leica 25mm f1.4 is 9 elements, twice the cost of a 45mm or 50mm f2.8 FF lens, and because it's f1.4 it needs twice the precision in assembly as the f2.8 FF lens. You then multiply that by (9/4)^2 to get the precision required for the increased number of elements. Put it all together, and the lens for the smaller sensor literally needs to be built to 10x the precision.

While this is in general true, there is a point at which the price performance trend for real lenses reverses, and this is the reason that phonecam lenses can perform so ridiculously well. There is a scale at which manufacturing techniques that would be totally impracticable at larger scales become feasible, at least if volumes are enormous. So, phonecam lenses often don't have many elements, but they have every single surface an extreme aspheric which can be precision moulded in a tiny lens because the thermal capacity is so small that the lens will not have serious cooling stresses and distortions. They can be assembled by micropositioning stages and achieve relative precisions impossible with bigger lenses, and so on. Very often these lenses are diffraction limited (which is a good thing for a lens to be).

 

[bobn2]

olliess wrote:

quadrox wrote:

In the end that means that medium format and large format only hold an advantage as long as DSLR lenses are not diffraction limited.

I think it's correct to say that we're getting to the point where DSLRs significantly affected by diffraction, and may even be said to be diffraction-limited at some apertures.

I don't think it's correct to say that, or at least, not meaningful. We are still well short of pixel counts such that the resolution of the lens is the limit over the whole aperture range. In any case, mostly, the lens is giving its best resolution (which present cameras cannot entirely capture) when it is aberration, not diffraction limited. This whole idea of cameras being 'diffraction limited' due to high pixel count is bogus. Diffraction is a property of the lens, not the camera. The job of a camera ideally is to capture all the information in the image projected by the lens and as yet we don't have any camera that will do that. Ideally lenses would be diffraction limited at all aperture settings, and we don't at present have any lenses that are.

 

[Olaf Ulrich]

quadrox wrote:
... I have now realized a good way to phrase my question so I might get good answers.

Ugh. As you already noted, your question-phrasing actually is pretty poor. So you got a couple of answers yet ... but hardly any useful ones.

.

quadrox wrote:
As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

1. All else being equal, smaller sensors will suffer more from diffraction when using a given f-stop ...

Yes.

.

quadrox wrote:
... due to smaller pixels.

No.

Instead, it's due to the format being smaller. Pixel size has nothing to do with it.

.

quadrox wrote:
All else being equal, smaller sensors have more depth-of-field at a given f-stop.

This statement doesn't make any sense—so no, there is no consensus of this being true or false. It's neither true nor false but just nonsense. Because it simply is not possible to keep everything else equal.

.

quadrox wrote:
Will equivalent photos taken at the same resolution, with the same field-of-view and depth-of-field have different amounts of diffraction?

Sure they will. However this is not the question you wanted to ask (talk about 'phrasing'!).

First of all, you'll need to understand the difference between diffraction and diffraction blur, the latter being the degree of loss of sharpness due to diffraction. So you don't want to know about diffraction but about diffraction blur.

And the answer to your (properly re-phrased) question is: No. When using equivalent focal lengths (i. e. same angle of view) and equivalent apertures (i. e. same depth-of-field) on cameras with different image formats then diffraction blur will be the same in the two cameras. Umm ... basically.

However if you look very close at the topic then you'll realize that perfect equivalence in terms of field-of-view and perspective and depth-of-field and diffraction blur is not possible; the best you can get is some approximation of equivalence (except at infinity focus). But then, for virtually all intents and purposes, you can get close enough.

.

quadrox wrote:
I see one alternative aspect where larger formats may yield higher resolution: Lens sharpness.

Again, a nonsense statement, so no true or false here.

.

quadrox wrote:
Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

Of course not! There are good and bad lenses for for small-format cameras, and there are good and bad lenses for for large-format cameras. The only difference is—the percentage of poor lenses is higher for small-format cameras (because many of these are made with low price being their primary selling point; less so for large-format cameras).

.

quadrox wrote:
And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from.

Now, doesn't your intuition tell you that your intuition obviously must be wrong!?

In fact, the point of using larger-format cameras is not superior resolution ... it's superior image quality. Resolution is only one single factor affecting image quality. There are many others, including (but not limited to) micro-contrast and richness of colour and tonality.

 

[olliess]

Bobn2 wrote:

olliess wrote:

quadrox wrote:

In the end that means that medium format and large format only hold an advantage as long as DSLR lenses are not diffraction limited.

I think it's correct to say that we're getting to the point where DSLRs significantly affected by diffraction, and may even be said to be diffraction-limited at some apertures.

I don't think it's correct to say that, or at least, not meaningful. We are still well short of pixel counts such that the resolution of the lens is the limit over the whole aperture range.

I didn't say "over the whole aperture range," I said "at some apertures."

In any case, mostly, the lens is giving its best resolution (which present cameras cannot entirely capture) when it is aberration, not diffraction limited.

Sure.

This whole idea of cameras being 'diffraction limited' due to high pixel count is bogus. Diffraction is a property of the lens, not the camera.

The camera isn't diffraction limited DUE to higher pixel counts. It's diffraction that is limiting your ability to gain much more from higher pixel counts.