Diffraction Limit

Started Aug 28, 2013 | Discussions
LTZ470
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Diffraction Limit
Aug 28, 2013

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

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LTZ470
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Re: Steen Bay
In reply to LTZ470, Aug 28, 2013

Hallalujah!..Someone with a clue!

Steen Bay wrote:

"Also depends on where you look. The lens aberrations are usually stronger in the corners than in the center, so the point at which the resolution starts to decrease will most often be at a smaller aperture if looking at the border/corner resolution."

"@LTZ470 - Is the FZ200 also sharpest at f/4 in the center, or are you just saying that the overall sharpness is best at f/4?"

Yes in the center is the sharpest, and correct, the corners suffer, from what I can tell...especially when you add the TC-E17ED...the TC-E15ED didn't seem so bad, I suspect the TC is magnifying any defects/aberrations already present in the lens...

One photo that had me scratching my head, shot of tripod, sharp center, blurred left hand side, and still on pane with subject:

I can't see a Turtle moving his head fast enough to blur? at 1/1000 shutter, just don't seem possible...

Same shot SX50:

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Anders W
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Re: Diffraction Limit
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

You think this is a very credible source?

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

Have a look here:

http://www.dpreview.com/forums/post/51853899

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Great Bustard
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Speaking of clues...
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

Hallalujah!..Someone with a clue!

Steen Bay wrote:

"Also depends on where you look. The lens aberrations are usually stronger in the corners than in the center, so the point at which the resolution starts to decrease will most often be at a smaller aperture if looking at the border/corner resolution."

Yes, Steen did write that, didn't he? He wrote it in this post:

http://www.dpreview.com/forums/post/52061974

where he is responding to me, where I quote from the Equivalence Essay (I'm the author, by the way) on diffraction:

http://www.josephjamesphotography.com/equivalence/#diffraction

Diffraction softening is unavoidable at any aperture, and worsens as the lens is stopped down. However, other factors mask the effects of the increasing diffraction softening: the increasing DOF and the lessening lens aberrations.

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In terms of cross-format comparisons, all systems suffer the same from diffraction softening at the same DOF. This does not mean that all systems resolve the same detail at the same DOF, as diffraction softening is but one of many sources of blur (lens aberrations, motion blur, large pixels, etc.). However, the more we stop down (the deeper the DOF), diffraction increasingly becomes the dominant source of blur. By the time we reach the equivalent of f/32 on FF (f/22 on APS-C, f/16 on mFT and 4/3), the differences in resolution between systems is trivial.

Let me now fill in the "..." from the same link (please excuse the repetition, and take care to note the portion I highlighted in bold which was omitted from the first quote, as it was not particularly relevant at the time -- in fact, there's a lot more about diffraction in that link that I also did not quote, which, in fact, is why I gave the link):

Diffraction softening is unavoidable at any aperture, and worsens as the lens is stopped down. However, other factors mask the effects of the increasing diffraction softening: the increasing DOF and the lessening lens aberrations. As the DOF increases, more and more of the photo is rendered "in focus", making the photo appear sharper. In addition, as the aperture narrows, the aberrations in the lens lessen. For wide apertures, the increasing DOF and lessening lens aberrations far outweigh the effects of diffraction softening. At small apertures, the reverse is true. In the interim (usually around a two stop interval), the two effects roughly cancel each other out, and the balance point for the edges typically lags the balance point for the center by around a stop (the edges usually suffer greater aberrations than the center). In fact, it is not uncommon for diffraction softening to be dominant right from wide open for lenses slower than f/5.6 equivalent on FF, and thus these lenses are sharpest wide open (for the portions of the scene within the DOF, of course).

The optimum DOF is often more a matter of artistic intent than resolved detail. Clearly, more shallow DOFs have less of the scene within critical focus, but this is by design. What is not by design is that, at very wider apertures, lens aberrations reduce the detail even for the portions of the scene within the DOF, so even if the photographer prefers the more shallow DOF, they may choose to stop down simply to render more detail where detail is important. Likewise, while a photographer may stop down with the intent to get as much of the scene as possible within the DOF so as to have a more detailed photo, portions of the scene that were within the DOF at wider apertures will ne softer due to the effects of diffraction, so the photographer must balance the increase in detail gained by bringing more of the scene within the DOF against loosing detail for portions of the scene that were within the DOF at wider apertures. In addition, deeper DOFs require smaller apertures, which means either longer shutter speeds (increasing the risk/amount of motion blur and/or camera shake) or greater noise since less light will fall on the sensor at more narrow apertures for a given shutter speed.

However, the relationship between diffraction softening and pixel density is largely misunderstood. For a given sensor size and lens, more pixels always result in more detail. As we stop down and the DOF deepens, we reach a point where we begin to lose detail due to diffraction softening. As a consequence, photos made with more pixels will begin to lose their detail advantage earlier and quicker than images made with fewer pixels, but they will always retain more detail. Eventually, the additional detail afforded by the extra pixels becomes trivial (most certainly by f/32 on FF). See here for an excellent example of the effect of pixel size on diffraction softening.

In terms of cross-format comparisons, all systems suffer the same from diffraction softening at the same DOF. This does not mean that all systems resolve the same detail at the same DOF, as diffraction softening is but one of many sources of blur (lens aberrations, motion blur, large pixels, etc.). However, the more we stop down (the deeper the DOF), diffraction increasingly becomes the dominant source of blur. By the time we reach the equivalent of f/32 on FF (f/22 on APS-C, f/16 on mFT and 4/3), the differences in resolution between systems is trivial.

Imagine that. I found it terribly curious that Steen felt it necessary to add that tidbit in, as it didn't really pertain to the situation at hand, except as an aside, when it was contained within the link I gave.

Furthermore, let me quote more from my post:

In short, it is entirely possible for the FZ200 to be sharper at f/4 than it is at f/2.8, even though at f/2.8 it is already well within the realm of strong diffraction softening, and the lesser lens aberrations at f/4 may outweigh the increased diffraction softening.

Regardless, the effects of diffraction softening at f/2.8 on an FZ200 are identical to the effects of diffraction softening at f/8 on mFT and f/16 on FF, it's just that diffraction softening is one of many forms of blur.

So, where does that leave us? Oh yes -- it leaves us back where we started: you do not understand diffraction in the least.

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Alan_W1
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Re: Steen Bay
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

One photo that had me scratching my head, shot of tripod, sharp center, blurred left hand side, and still on pane with subject:

I can't see a Turtle moving his head fast enough to blur? at 1/1000 shutter, just don't seem possible...

Same shot SX50:

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Pretty sure this is localised evaporation causing this selective blur. Its not always noticable on stills, but I very frequently have to deal with it when shooting video near water.

Shallow water, and with a subject being small/close to the surface is very prone to this selective degrading. Its intensity is very variable and continually fluctuates, depending on a number of factors.

I have a vast amount of "real world" examples of this { video, with frame grabs showing this type of very localised atmospheric fluctuation/degrading} which I could post, but suspect it could divert your thread somewhat {as this thread is likely to become a slide rule/calculator type of thread}, so shall leave it for another day/thread.

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Anders W
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Re: Speaking of clues...
In reply to Great Bustard, Aug 28, 2013

Great Bustard wrote:

So, where does that leave us? Oh yes -- it leaves us back where we started: you do not understand diffraction in the least.

If that were the only thing he doesn't understand, the situation would be vastly improved. Regrettably it isn't.

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Great Bustard
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Yep.
In reply to Anders W, Aug 28, 2013

Anders W wrote:

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

You think this is a very credible source?

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

Have a look here:

http://www.dpreview.com/forums/post/51853899

Bob's post (the second link) is really quite outstanding and to the point. Let's see if I can't sum diffraction softening up more neatly, if not as completely as Bob did:

  • There is no such thing as a "diffraction limit" except when the resolution falls to zero.
  • There is a point where diffraction softening becomes the dominant source of blur, and this point will vary from lens to lens, as well as where in the frame we are looking (the corners typically, but not always, lag about a stop behind the center for DSLR lenses).
  • All systems suffer the same diffraction softening at the same DOF.
  • More pixels, all else equal, will *always* resolve more detail.
  • All systems do not necessarily resolve equally at the same DOF, as diffraction is one of many sources of blur. However, as the DOF deepens, the resolution decreases, and the resolution differences between systems narrows, typically becoming trivial by f/16 on mFT (f/32 on FF and f/5.6 on an FZ200), regardless of how sharp the lens is or how many pixels the sensor has.
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Great Bustard
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Re: Speaking of clues...
In reply to Anders W, Aug 28, 2013

Anders W wrote:

Great Bustard wrote:

So, where does that leave us? Oh yes -- it leaves us back where we started: you do not understand diffraction in the least.

If that were the only thing he doesn't understand, the situation would be vastly improved. Regrettably it isn't.

There is no sin in not understanding.  The sin lies in refusing to learn.  The greater sin is to be proud of the first sin.

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Detail Man
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Re: Diffraction Effects in a Real Lens-Camera System
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

Ian was rightly setting-straight the poster on that thread who stated that Diffraction was a function of aperture diameter - which it is not, it is an (approximate, for larger F-Number values) function of the Focal Length divided the aperture diameter as measured from the outside of the lens (the entrance-pupil diameter). Also known as the lens-system F-Number.

The poster corrected in Ian's post seemed to have Diffraction mixed up with DOF - which is not surprising, given how the two subjects are often lumped together in what is an incomplete explananation. Those explanations do not take into account the lens-system MTF curve "extinction" effect (see below).

Regarding DOF. Smaller image-sensor cameras use lower valued F-Numbers than do larger image-sensor cameras (to achieve the same DOF with the same image-framing), so that situation is a "self-compensating" one.

Diffraction MTF response curve "extinction" does indeed result in a "fundamental resolution limit" - but only when the product of Wavelength multiplied by F-Number is fairly high - higher than you, or most other people, typically talk about (although this does indeed become relevant for smaller sized photosites when Wavelengths and F-Numbers are of a high numerical value).

In that "extinction" limit of spatial frequency response, it is Wavelength, F-Number, Photosite aperture, shape, and "pitch", as well as the de-mosaicing algorithm used that result in the (RAW-level) image-data, that then is further processed (in-camera, or in an external processor) to the point where we as viewers look at it appearing at some physical viewing-size from some distance with some unknown visual acuity, and (may) exclaim, "dad-gum that shore lookie sharp" !" ... Every single one of the above things (all) affect perceived image "sharpness" ...

When we talk about how images from specific camera-lens system appear (at least to our own eyeballs), all of the above listed things matter (in addition to all image-processing). Of course, we are also assuming zero focus-error on the Plane of Focus (which is not reality), and we are also assuming an effective zero amount of camera-motion (which is not reality). These things will typically "swamp" most effects from lens-diffraction into completely obscure irrelevance ...

I myself have learned a lot from listening to others and considering their thoughts and their viewpoints. Joe and Anders know a lot about these subjects. They are worth reading and listening to. I myself might be worth reading and listening to as well (have I ever "steered you wrong" ?). Have in the last few months given quite a bit of specific thought surrounding these subjects (here):

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

Keep the Fun,

DM ...

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Anders W
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Re: Speaking of clues...
In reply to Great Bustard, Aug 28, 2013

Great Bustard wrote:

Anders W wrote:

Great Bustard wrote:

So, where does that leave us? Oh yes -- it leaves us back where we started: you do not understand diffraction in the least.

If that were the only thing he doesn't understand, the situation would be vastly improved. Regrettably it isn't.

There is no sin in not understanding. The sin lies in refusing to learn. The greater sin is to be proud of the first sin.

Very good summary.

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Anders W
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Re: Yep.
In reply to Great Bustard, Aug 28, 2013

Great Bustard wrote:

Anders W wrote:

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

You think this is a very credible source?

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

Have a look here:

http://www.dpreview.com/forums/post/51853899

Bob's post (the second link) is really quite outstanding and to the point. Let's see if I can't sum diffraction softening up more neatly, if not as completely as Bob did:

  • There is no such thing as a "diffraction limit" except when the resolution falls to zero.
  • There is a point where diffraction softening becomes the dominant source of blur, and this point will vary from lens to lens, as well as where in the frame we are looking (the corners typically, but not always, lag about a stop behind the center for DSLR lenses).
  • All systems suffer the same diffraction softening at the same DOF.
  • More pixels, all else equal, will *always* resolve more detail.
  • All systems do not necessarily resolve equally at the same DOF, as diffraction is one of many sources of blur. However, as the DOF deepens, the resolution decreases, and the resolution differences between systems narrows, typically becoming trivial by f/16 on mFT (f/32 on FF and f/5.6 on an FZ200), regardless of how sharp the lens is or how many pixels the sensor has.

Another very good summary. Thanks for taking the time to put this so concisely.

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Paul De Bra
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The plain truth can indeed be phrased in very misleading ways...
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

This statement is absolutely factually correct. It is also a useless statement for anyone trying to decide which higher f-numbers to avoid to not suffer from softening due to diffraction.

Diffraction indeed defines how light is "scattered" over an area of the sensor, depending on the f-number. The size of the "airy disk" is independent of the number of megapixels or the size of the film format. But, now let's see whether that has influence on the image we can capture:

Suppose the diameter of the airy disk is X. If the size of our sensor is of the same order of magnitude as X the total image captured will have absolutely no detail whatsoever, even if that tiny X-sized sensor has 100MP. If the size of our sensor is in the order of 1000X we can resolve in the order of 1000 lines and get a fairly detailed image. The size of the airy disk is the same but on a larger sensor the *relative* size of that airy disk to the total size of the image is way smaller.

So what matters is the size of the airy disk that corresponds to a certain f-stop versus the size of the pixels relative to that airy disk. When you look at pixel-level detail of an image (which is not overall sharpness) what counts is the size of the pixels. Diffraction at the pixel level at say f/16 on a 12MP 4/3 sensor will be roughly equivalent to diffraction at f/16 on a 48MP 35mm full frame sensor, when you look at the image from the same distance relative to the pixel size. So if you look at a 30x20 print from that 12MP sensor from 2 feet you should look at a 60x40 print form the 48MP sensor from the same 2 feet.

Diffraction does play a different role on smaller versus larger sensors because the way I described above is not the way we look at pictures. We blow up the pictures captured by small sensors and/or shrink the pictures captured by large sensors so that the printed images are of the same size. When you do that we are effectively changing the effect the size of the airy disk has. We are blowing up the airy disk seen by the small sensor and/or shrink the airy disk seen by the larger sensor. Which means that the diffraction caused by a certain f-stop becomes much more visible in the blown-up image from the small sensor and less visible in the shrunk image from the larger sensor.

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

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Great Bustard
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Re: The plain truth can indeed be phrased in very misleading ways...
In reply to Paul De Bra, Aug 28, 2013

Paul De Bra wrote:

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

This statement is absolutely factually correct. It is also a useless statement for anyone trying to decide which higher f-numbers to avoid to not suffer from softening due to diffraction.

Diffraction indeed defines how light is "scattered" over an area of the sensor, depending on the f-number. The size of the "airy disk" is independent of the number of megapixels or the size of the film format. But, now let's see whether that has influence on the image we can capture:

Suppose the diameter of the airy disk is X. If the size of our sensor is of the same order of magnitude as X the total image captured will have absolutely no detail whatsoever, even if that tiny X-sized sensor has 100MP. If the size of our sensor is in the order of 1000X we can resolve in the order of 1000 lines and get a fairly detailed image. The size of the airy disk is the same but on a larger sensor the *relative* size of that airy disk to the total size of the image is way smaller.

So what matters is the size of the airy disk that corresponds to a certain f-stop versus the size of the pixels relative to that airy disk.

Not the size of the pixels, but the size of the Airy Disk as a proportion of the sensor size. Smaller pixels, for a given sensor size, always resolve more detail at any given f-ratio.

When you look at pixel-level detail of an image (which is not overall sharpness) what counts is the size of the pixels. Diffraction at the pixel level at say f/16 on a 12MP 4/3 sensor will be roughly equivalent to diffraction at f/16 on a 48MP 35mm full frame sensor, when you look at the image from the same distance relative to the pixel size. So if you look at a 30x20 print from that 12MP sensor from 2 feet you should look at a 60x40 print form the 48MP sensor from the same 2 feet.

Diffraction does play a different role on smaller versus larger sensors because the way I described above is not the way we look at pictures. We blow up the pictures captured by small sensors and/or shrink the pictures captured by large sensors so that the printed images are of the same size. When you do that we are effectively changing the effect the size of the airy disk has. We are blowing up the airy disk seen by the small sensor and/or shrink the airy disk seen by the larger sensor. Which means that the diffraction caused by a certain f-stop becomes much more visible in the blown-up image from the small sensor and less visible in the shrunk image from the larger sensor.

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

Let's see if this doesn't sum it up:

http://www.josephjamesphotography.com/equivalence/index.htm#diffraction

In addition to DOF and sharpness, the is also intimately connected to diffraction. Diffraction softening is the result of the wave nature of light representing point sources as disks (known as Airy Disks), and is most definitely not, as is misunderstood by many, an effect of light "bouncing off" the aperture blades. The diameter of the Airy Disk is a function of both the f-ratio and the wavelength of light: d ~ 2.44·λ·f, where d is the diameter of the Airy Disk, λ is the wavelength of the light, and f is the f-ratio. Larger f-ratios (deeper DOFs) result in larger disks, as do longer wavelengths of light (towards the red end of the visible spectrum) so not all colors will suffer from diffraction softening equally. The wavelengths of light in the visible spectrum differ by approximately a factor of two, so that means, for example, that red light will suffer around twice the amount of diffraction softening as blue light.

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.

While the diameter of the Airy Disk is the same for the same color and f-ratio, regardless of the sensor size, the effect of the diffraction softening is not the same across formats. The reason is that the proportion of the sensor that is covered by the Airy Disk is not the same since the sensors are not the same size. For example, while the Airy Disk diameter at the same f-ratio, the effect of the diffraction softening on 35mm FF is half as much as on 4/3, if the final images are displayed with the same diagonal dimension, .

Let's work an example using green light (λ = 530 nm = 0.00053mm). The diameter of the Airy Disk at f/8 is 2.44·0.00053mm·8 = 0.0103mm, and the diameter of the Airy Disk at f/4 is half as much -- 0.0052mm. For FF, the diameter of the Airy Disk represents 0.0103mm / 43.3mm = 0.024% of the sensor diagonal at f/8 and 0.005mm / 21.6mm = 0.012% of the diagonal at f/4. For 4/3, the diameter of the Airy Disk represents 0.0103mm / 21.6mm = 0.048% at f/8 and 0.005mm / 21.6mm = 0.024% at f/4.

Thus, at the same f-ratio, we can see that the diameter of the Airy Disk represents half the proportion on FF as 4/3, but at the same DOF, the diameter of the Airy Disk represents the same proportion of the sensor. In other words, all systems will suffer the same amount of diffraction softening at the same DOF and display dimensions. However, the system that began with more resolution will always retain more resolution, but that resolution will asymptotically vanish as the DOF deepens. In absolute terms, the earliest we will notice the effects of diffraction softening is when the diameter of the Airy Disk exceeds that of a pixel (two pixels for a Bayer CFA), but, depending on how large the photo is displayed, we may not notice until the diameter of the Airy Disk is much larger.

In addition, it's important to note that, for two sensors of a given size, the sensor with a greater pixel density does not suffer more from diffraction softening due to the smaller pixels. We will simply notice the effects of diffraction softening earlier (at wider apertures) since we had more resolution to begin with as a result of the smaller pixels (presuming, of course, that we display the photo large enough that we can resolve individual pixels). Of course, the effects of diffraction softening are also offset by lessening lens aberrations (to a point) as well as more of the photo coming within the DOF as we stop down.

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LTZ470
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Re: Diffraction Effects in a Real Lens-Camera System
In reply to Detail Man, Aug 28, 2013

Know a lot or think they "know" a lot? Love it when the school boys come out to play!

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LTZ470
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Re: The plain truth can indeed be phrased in very misleading ways...
In reply to Paul De Bra, Aug 28, 2013

Paul De Bra wrote:

LTZ470 wrote:

From a very credible source:

"Diffraction thus sets a fundamental resolution limit that is independent of the number of megapixels, or the size of the film format. It depends only on the f-number of your lens, and on the wavelength of light being imaged. "

This statement is absolutely factually correct. It is also a useless statement for anyone trying to decide which higher f-numbers to avoid to not suffer from softening due to diffraction.

Diffraction indeed defines how light is "scattered" over an area of the sensor, depending on the f-number. The size of the "airy disk" is independent of the number of megapixels or the size of the film format. But, now let's see whether that has influence on the image we can capture:

Suppose the diameter of the airy disk is X. If the size of our sensor is of the same order of magnitude as X the total image captured will have absolutely no detail whatsoever, even if that tiny X-sized sensor has 100MP. If the size of our sensor is in the order of 1000X we can resolve in the order of 1000 lines and get a fairly detailed image. The size of the airy disk is the same but on a larger sensor the *relative* size of that airy disk to the total size of the image is way smaller.

So what matters is the size of the airy disk that corresponds to a certain f-stop versus the size of the pixels relative to that airy disk. When you look at pixel-level detail of an image (which is not overall sharpness) what counts is the size of the pixels. Diffraction at the pixel level at say f/16 on a 12MP 4/3 sensor will be roughly equivalent to diffraction at f/16 on a 48MP 35mm full frame sensor, when you look at the image from the same distance relative to the pixel size. So if you look at a 30x20 print from that 12MP sensor from 2 feet you should look at a 60x40 print form the 48MP sensor from the same 2 feet.

Diffraction does play a different role on smaller versus larger sensors because the way I described above is not the way we look at pictures. We blow up the pictures captured by small sensors and/or shrink the pictures captured by large sensors so that the printed images are of the same size. When you do that we are effectively changing the effect the size of the airy disk has. We are blowing up the airy disk seen by the small sensor and/or shrink the airy disk seen by the larger sensor. Which means that the diffraction caused by a certain f-stop becomes much more visible in the blown-up image from the small sensor and less visible in the shrunk image from the larger sensor.

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

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A man after my own heart...common sense at it's best! The last batch we printed for the Heard Museum was all 4X6 and 5X7...sharp as a tack and we have received nothing but compliments from them...

The max we would ever print a 1/2.3 sensor sized photo would be 8X10, and I have printed "one" of those in the last 5 yrs...it is very nice and not quite sharp as it came from FZ100 (16mp sensor)...but the colors are very nice...if from the FZ200 or FZ150 it would have been sharper for sure...due to 12mp sensor...

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Anders W
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Re: Diffraction Effects in a Real Lens-Camera System
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

Know a lot or think they "know" a lot? Love it when the school boys come out to play!

http://www.dpreview.com/forums/post/52064042

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Re: The plain truth can indeed be phrased in very misleading ways...
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

A man after my own heart...common sense at it's best!

So you are starting to see at least parts of the light after all?

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Detail Man
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Re: Diffraction Effects in a Real Lens-Camera System
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

Know a lot or think they "know" a lot? Love it when the school boys come out to play!

The usefulness of the above "calculator" has been debunked a multitude of times on DPReview Forums. The most recent example of that was on this particular recent Open Talk thread here:

http://www.dpreview.com/forums/thread/3520761

... on which I posted this (if you really want to get into the numbers that actually matter):

http://www.dpreview.com/forums/post/51858399

It is a mistake to assume that some given website (including "Cambridge In Color" and "Luminous Landscape" must surely define shining "absolute truth". In fact, there are certain posters on these (as well as the LL) forums who actually understand these subjects well, and in fact know a lot more about these subjects than the offerings of many, many web-sites and web-blogs.

Complicated subjects cannot be easily simplified - and it is thus a mistake to wrongly assume so.

It is possible to better understand these subjects - but it is necessary to make the (non-trivial) effort of reading and thinking about and trying to understand what these folks are actually talking about.

I have myself provided you with a huge amount of specific and accurate information in the last few days, and linked you to even more reliable information. What Anders and Joe are saying to you is not untrue (though I do indeed think that there are just a few things in Joe's method of explanation that are well served by some further surrounding facts also being mentioned).

All in all, there is much to learn before one can even imagine to begin to "teach" others about complicated subjects. Humbling it can be. It has been for me. It likely is for any intelligent participant.

DM ...

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LTZ470
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Re: The plain truth can indeed be phrased in very misleading ways...
In reply to Anders W, Aug 28, 2013

Anders W wrote:

LTZ470 wrote:

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

A man after my own heart...common sense at it's best!

So you are starting to see at least parts of the light after all?

I've always had the light...it's the BS one has to filter out...

GB wrote:

In short, it is entirely possible for the FZ200 to be sharper at f/4 than it is at f/2.8, even though at f/2.8 it is already well within the realm of strong diffraction softening, and the lesser lens aberrations at f/4 may outweigh the increased diffraction softening.

Regardless, the effects of diffraction softening at f/2.8 on an FZ200 are identical to the effects of diffraction softening at f/8 on mFT and f/16 on FF, it's just that diffraction softening is one of many forms of blur.

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Re: The plain truth can indeed be phrased in very misleading ways...
In reply to LTZ470, Aug 28, 2013

LTZ470 wrote:

Anders W wrote:

LTZ470 wrote:

So while the "fundamental" statement is correct the reality is that smaller sensors suffer from diffraction at larger apertures than large sensors because we change the magnification of the image captured by the surface of the sensor.

A man after my own heart...common sense at it's best!

So you are starting to see at least parts of the light after all?

I've always had the light...

Don't know whether you had it but you sure didn't see it.

it's the BS one has to filter out...

Agreed.

GB wrote:

In short, it is entirely possible for the FZ200 to be sharper at f/4 than it is at f/2.8, even though at f/2.8 it is already well within the realm of strong diffraction softening, and the lesser lens aberrations at f/4 may outweigh the increased diffraction softening.

Regardless, the effects of diffraction softening at f/2.8 on an FZ200 are identical to the effects of diffraction softening at f/8 on mFT and f/16 on FF, it's just that diffraction softening is one of many forms of blur.

As long as you consider this part of the light, we are in full agreement here too.

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