I don't worry about lens diffraction at all these days, because I have found with modern high capacity sensors and a reasonably good sharpening technique, as far as I can see, it is no longer an issue IMHO - unless you are a canvas sniffer that is :) A jocular term I once heard someone using to refer to other landscape photographers (that would be you and me!), that he would often see inspecting his work in his gallery, with their noses about an inch away from the pictures.
In fact I would even go as far as to say, that with modern sensors (of the Sony persuasion at least) the uncompressed Raw straight out of the camera and without any in-camera sharpening, can still look a little too sharp to me on occasions, so sometimes I find myself even adding a little bit of negative clarity ;)
... Stopping down to f/16 is a good way to convert a 46 MP Nikon D850 to the equivalent of a 7 MP camera such as the Nikon D70...
I wonder how representative are the Rodenstock lens examples relative to other lenses. So while the article is interesting and insightful, a Canon 50mm F1.4 lens, used by many more shooters, might have very different characteristics.
Maybe Lula could open up a new technical section - Lens Performance Examples, and various members could contribute similar images based on their experiments for Nikon, Canon, Sony, Sigma, FF, APS-C and M43 lenses - 20mm, 35mm, 50mm, 85mm, etc.
Crowd-sourcing project, though it would require a part-time administrator, but the result could be a very comprehensive and useful lens reference library. Available Only On LuLa.
Apart from that seemingly scholastic argument, has anyone actually done any comparison in prints of various sizes to prove the above? At which print size people wouldn’t be able to distinguish 7 Mp from 46 Mp?
So much of the sharpness lost to diffraction can be restored by advanced sharpening.
I would like to elaborate, but cannot find the time right now...
I think you have it backwards. To take advantage of modern high resolution sensors one should keep the Airy disc diameter no greater than twice the pixel pitch. George Douvos has published an excellent article (http://www.georgedouvos.com/douvos/Depth_of_Field,_Diffraction_and_High_Resolution_Sensors.html) on this subject. Stopping down to f/16 is a good way to convert a 46 MP Nikon D850 to the equivalent of a 7 MP camera such as the Nikon D70. See figure 3 of this post (https://luminous-landscape.com/do-sensors-out-resolve-lenses/).
Cheers,
Bill
Has anyone else noticed that depth of field appears unchanged in all the examples in the article?
Stopping down to f/16 is a good way to convert a 46 MP Nikon D850 to the equivalent of a 7 MP camera such as the Nikon D70.
Has anyone else noticed that depth of field appears unchanged in all the examples in the article?
Well I am sorry to disagree with you Bill, but I think you are entirely wrong in this case if all you are suggesting we do is base our view of photography on such meaningless technical issues, which may indeed be absolutely correct in a science over aesthetics sort of way. Because I would argue long and hard, that photography is no longer about attaining eye watering sharpness anymore, or the technical performance of exotic overpriced lenses and camera bodies, as that ship has sailed and now even the most basic system has evolved way beyond the abilities of your average Joe photographer these days. So it is now once again (and as it should be IMHO), more about the picture and the art of photography than it is about the kit and so anyone should be able do it reasonably well with a keen eye and a reasonably priced system, that compared to the equipment of old, has gone well beyond what most of us should ever need. I mean if Ansel was alive today, I don't think you or I or anyone else for that matter, would be telling him that his pictures aren't very good, because they're not very sharp or a high enough pixel density?
Dave
Dave,
When I made the post, I already knew that you would disagree. An interesting article (https://www.nytimes.com/2007/02/08/technology/08pogue.html?auth=login-smartlock) on megapixels was published in the New York Times in 2007 (I think that is before they began posting fake news :) ). He did a blinded study and concluded that 6-8 megapixels was sufficient. If this were true, I don't know why anyone would pay US $50,000 for a Phase One IQ4 that is advertised on the opening page of this forum. In any case, LuLa is happy to accept their advertising fee.
Lloyd Chambers (Diglloyd) has written extensively on the effects of diffraction on his pay web site. In a study with the Nikon D7100 (a 24 MP crop frame whose pixel density would result in 56 MP in a full frame camera) with the Zeiss 135 mm f/2 plan apo (perhaps the sharpest available lens at that time) he noted dulling of the image at f/8, even with aggressive deconvolution sharpening. A dull haze was noted at f/11 and f/16 and f/22 showed severe degradation.
I have done my own tests with this lens with my Nikon D850 using Bart Vanderwolf's sinusoidal Siemen's star. Wilth this target, resolution at a MTF of about 10% is proportional to the diameter of the extinction radius. These images are considerably cropped from the full frame to show the area of interest. At f/4 the system resolves to Nyquist, 102 lp/mm with good contrast. Deconvolution sharpening with FocusMagic improves contrast. At f/22 resolution drops to 72 lp/mm with low contrast. FocusMagic can improve contrast, but resolution remains at 72 lp/mm.
[snip]
Proper deconvolution sharpening can partially reverse diffraction, but not completely as shown by my test and by Diglloyd's work.
Of course, you will say that proper deconvolution was not applied. What algorithm and PSF do you use?
Cheers,
Bill
Apart from that seemingly scholastic argument, has anyone actually done any comparison in prints of various sizes to prove the above? At which print size people wouldn’t be able to distinguish 7 Mp from 46 Mp?
Apart from that seemingly scholastic argument, has anyone actually done any comparison in prints of various sizes to prove the above? At which print size people wouldn’t be able to distinguish 7 Mp from 46 Mp?
Thanks, Erik, but that is not what I am asking. That’s just another scholastic calculation. As a practicing photographer, who did 24” x 36” from an 8 Mp camera, I got tired of theoretical calculations which would say such a print would look like sh*t. It doesn’t.
What am am suggesting is a visual comparison, a blind test, involving a group of people, photographers and non-photographers, trying to differentiate at which size they would start seeing a difference in prints between:*
- a 7 Mp camera shot at a difraction-optimal aperture and
- a 46 Mp camera shot at f/16
Ceteris paribus, of course.
* something similar to what Michael Reichmann did with Canon G10 and a medium-format Hasselblad, years ago.
Well I am sorry to disagree with you Bill, but I think you are entirely wrong in this case if all you are suggesting we do is base our view of photography on such meaningless technical issues, which may indeed be absolutely correct in a science over aesthetics sort of way. Because I would argue long and hard, that photography is no longer about attaining eye watering sharpness anymore, or the technical performance of exotic overpriced lenses and camera bodies, as that ship has sailed and now even the most basic system has evolved way beyond the abilities of your average Joe photographer these days. So it is now once again (and as it should be IMHO), more about the picture and the art of photography than it is about the kit and so anyone should be able do it reasonably well with a keen eye and a reasonably priced system, that compared to the equipment of old, has gone well beyond what most of us should ever need. I mean if Ansel was alive today, I don't think you or I or anyone else for that matter, would be telling him that his pictures aren't very good, because they're not very sharp or a high enough pixel density?
Dave
Aperture is you variable AA filter. The more you stop down, the stronger AA.
Except that in the case of the D850, Moire will be much less of an issue
... I see a camera as, to some extent, a device for capturing data. When I have that data I can do what I want with it - make a sharp picture, make a blurry picture, whatever. If I don't have the data, I have no choice...
Or is it that it just doesn't decrease as fast as the overall area of the shutter opening?
terror about diffraction is for astronomers.
Difficult to understand the reluctance of people to accept that diffraction is a real phenomenon that affects photographs! Why not just do a quick calculation for your sensor etc. and see what limits on aperture are indicated for situations that are relevant to you (numerous apps do this) and then bear this in mind when you're shooting?
The moment that Nyquist thingy appears my mind gets mushier than an image shot at f64.
Here is my way of working. Depth of field I control mostly with aperture as the other controls over depth of field, namely focal length of lens and distance to the subject, have been determined by other creative or practical considerations. I decide how much or how little I require in focus and where I want that focus to be and choose my aperture accordingly. I am sure that you are correct that a larger aperture will be sharper due to less diffraction but will the distant tree be sharper at f22 or f5,6 when I have selected to focus on an important foreground element? Yes the rock I focused on 5m away will be sharper at 5,6 than at f22 but what about the tree 100 meters away, at what aperture will it be sharper when my focus remains on the rock? At 5,6 or 22?
We are not talking about absolute sharpness with no context for goodness sakes. And yes I do know about field cameras, I bought my first one when I was 18, forty years ago. I am also aware of focus stacking, a more tedious endeavor than peeling grapes. Aperture is an exposure and depth of field control, shutter speed is an exposure and motion blur control, terror about diffraction is for astronomers.
Now and again I take a reasonable photo. No one ever said, “Nice shot, shame about the diffraction”.
Difficult to understand the reluctance of people to accept that diffraction is a real phenomenon that affects photographs! Why not just do a quick calculation for your sensor etc. and see what limits on aperture are indicated for situations that are relevant to you (numerous apps do this) and then bear this in mind when you're shooting?
I agree wholeheartedly with you; don't forget, though, that we are/were full-time professional photographers where getting the shot done and dusted was what counted rather thanesoteric number crunchingacquiring the optimal image.
I agree. Diffraction sucks the life out of an image (loss of micro-detail), but there is some mitigation possible with proper (deconvolution) sharpening. Not all images need to be technically perfect, but when given a choice, why not go for the better result?
My rule of thumb is based on that I can see the onset of diffraction losses when the diffraction pattern diameter (at the first zero ring) exceeds 1.5x the photosite pitch. That means that, approximately, pitch x 1.108 is the Aperture number where (green wavelength) diffraction becomes visible as loss of contrast. It can still be mostly compensated for, but it's gradually down-hill from there with narrower apertures until even high contrast detail cannot be resolved anymore. One might as well have used a lower resolution sensor.
MTF will go to zero at the following (circular) aperture:
N = 1 / (cycles_per_mm x wavelength)
The cycles / mm are given by the photosite pitch, e.g. 6.4 micron pitch equals (1 / 0.0064) / 2 = 78.125 cy/mm. In that case, the limiting aperture becomes 1 / (78.125 x 0.000555) = 23.063, so at approx. f/22 for green light (555 nm).
Cheers,
Bart
My point is an object 100 m away from where you focused is less sharp at f5,6 than it is at f22 even if there is less diffraction at f5,6.It may be. It may not be.
If the aim is sharpness can you not understand that a greater depth of field can be better than zero diffraction but totally blurred due to extremely shallow depth of field?Good plan. Sometimes if I want to get somewhere really quick I say to hell with gravity and jump over buildings :-)
Every new lens I buy I set up and check sharpness at every aperture. I then know that below a certain point that I will get diffraction issues. However if I think a greater depth of field is more important then to hell with diffraction.
It’s not a tough concept. Photography has always been about balancing technical capabilities of the medium against the message.True, but that is another issue. The question here is how to obtain the most technically perfect image, and that is by considering the relative influences of factors which degrade the image.
+1
For the Nikon D850 with a pixel pitch of 4.35 microns, the Nyquist is 115 cy/mm and the limiting aperture as calculated above is f/16 with a MTF of zero. I'm not certain what an MTF of zero means. At f/16 one can still see considerable detail in a D850 image at f/16.
I agree wholeheartedly with you; don't forget, though, that we are/were full-time professional photographers where getting the shot done and dusted was what counted rather than esoteric number crunching. The challenges were all of an entirely different nature, many starting well before we got to shooting that job.
Different mindset.
Rob
Hi Bill,
An MTF of zero, in this context, means that there is no discernible detail left at spatial frequencies at or above that cut-off point (Nyquist in this case) due to diffraction. Larger detail will be recorded, but with low contrast. So significant deconvolution sharpening is required to make the most of it. So it's a diffraction-limited MTF.
Here is an article about it:
http://spie.org/publications/tt52_151_diffraction_mtf?SSO=1
This would be ideal for suppression of aliasing (but with severe loss of contrast). That can be helpful as an additional security shot for subjects that give rise to aliasing, so one can create a repair layer and brush or blend away local aliasing artifacts. I use it with architecture, where a window can exhibit aliasing artifacts e.g. because there is a sunshade with a regular pattern, or bricks walls at an angle. So I take a normal shot at a wider aperture for higher resolution, and a safety shot at the diffraction cut-off aperture.
Cheers,
Bart
Bart,
Thanks for the clarification and your method of taking an additional security shot at a smaller aperture.
BTW, did you see my previous post in this thread using your sinusoidal Siemens star. Your comments would be appreciated.
https://forum.luminous-landscape.com/index.php?topic=130733.msg1111937#msg1111937
Hi Bart,
When calculating diffraction-limited MTF should we not take the Bayer demosaicing into account; not taking the actual pixel pitch into the equation but the distance between the individual green pixels, the distance between the individual red pixels etc?
For green light you’d get a pixel pitch * 1.4 (over the diagonal) and for red/blue light a pixel pitch * 2.
Also, there may be an additional effect due to the applied microlenses where the pixel is not sensitive near the edges and all the more near the centre.
What’s your idea on this?
I agree 100% with Island Dave on this one.
Worrying about those things is a crippling influence that, unless you are making huge blow-ups for hospital corridors etc. mean nothing - at least to me...
Rob
There are two types of people when it comes to choice: maximizers and satisfiers. You are apparently a maximizer. Maximizers won't stop until they find the best among available choices. Satisfiers (like me) stop when they find good enough. Maximizers tend to spend more time deliberating and choosing, Satisfiers choose quicker and move on to do something with the chosen.
Apart from that seemingly scholastic argument, has anyone actually done any comparison in prints of various sizes to prove the above? At which print size people wouldn’t be able to distinguish 7 Mp from 46 Mp?
This would be interesting... and combining this with viewing distance. This is a big factor.
Peter
Thanks Rob and Slobodan for agreeing with me and my relaxed attitude and advice to such things as diffraction, and how due to modern equipment, these things have now become something of a none issue - well to my mind at least ;)
Which part of "modern equipment" do you suppose eliminates the effect of diffraction?
You are of course free to be as relaxed as you like about your photography activities, but the laws of physics don't depend on your mental state :-)
Modern sensor technology such as the BSI sensor, which I am now happily using with the A7R2. Because by shifting the electronics to the back of the sensor, this means that the photosites can be placed much shallower within the front of the sensor and so the light travelling into those photosites, can still be successfully captured at a much lower angles of entry without as many detrimental effects
(https://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Comparison_backside_illumination.svg/220px-Comparison_backside_illumination.svg.png)
thereby greatly reducing the effects of diffraction and colour fringing when stopping down - plus when added to the updated CA reduction algorithms in PS, means almost no fringing at all even when shooting at f/16 or even f/22 on my old lenses.
Aslo when shooting with a high density 42mp sensor without AA filters (that also happens to capture something like 14.5 stops of dynamic range), I can also get a much sharper image straight off the card. So my old (and original version) 16-35 L 2.8, is like shooting with a new lens on the A7R2, whereas it was almost unusable on the 5D MkII I was using before.
No but good images often do ;)
Dave
Hi,
BSI will not affect diffraction. Diffraction is simply a property of light.
Essentially, diffraction is determined by the aperture, the wavelength of the light and nothing else.
At some aperture, the effects of diffraction dominate over lens aberration. With good lenses that happens at f/4 to f/5.6. The better the lens, the greater the effect will be.
Here is a great example from Jim Kasson's test of the Fuji GF 100/2 lens:
[snip]
The Nikon lens produces best MTF 50 at f/4, around 2200 cy/PH, stopped down to f/11 it reaches 1700 cy/PH. Essentially the same as the Fuji 50 GFX with the 110/2 at f/11.
Just to say, 1700 cy/PH is still pretty good...
Best regards
Erik
Best regards
Erik
Hi,
BSI will not affect diffraction. Diffraction is simply a property of light.
Essentially, diffraction is determined by the aperture, the wavelength of the light and nothing else.
...No but good images often do ;)
Well I can only tell you what my eyes are seeing, as I have no other way to measure this, nor would I want to waste any time trying to do so.
Just look at the shot I posted several pages ago on this thread, is it sharp enough? Yes I think so. Are there any diffraction or CA issues within it? Well not that I can see. So yes you may be able to show me graphs and scientific papers that tell me the physics are saying one thing, but all I can say is that my eyes are telling me that with this sensor and these old lenses, that CA and diffraction etc, are no longer an issue worth worrying about.
But of course Erik, if you wish to worry about these issues, then that is fair enough and I would not wish to argue with you or anyone else on this, but for me, it simply comes down to the technology having now evolved to the point, where it has become good enough for such technical considerations as these, to have become a thing of the past.
all the best everyone :) :)
Dave
No but good images often do ;)
Dave
I agree. Diffraction sucks the life out of an image (loss of micro-detail), but there is some mitigation possible with proper (deconvolution) sharpening. Not all images need to be technically perfect, but when given a choice, why not go for the better result?
My rule of thumb is based on that I can see the onset of diffraction losses when the diffraction pattern diameter (at the first zero ring) exceeds 1.5x the photosite pitch. That means that, approximately, pitch x 1.108 is the Aperture number where (green wavelength) diffraction becomes visible as loss of contrast. It can still be mostly compensated for, but it's gradually down-hill from there with narrower apertures until even high contrast detail cannot be resolved anymore. One might as well have used a lower resolution sensor.
MTF will go to zero at the following (circular) aperture:
N = 1 / (cycles_per_mm x wavelength)
One of the problems (in my opinion) with discussions of this type are phrases and words like "sucks the life out of" and "better." I have hanging on my living room wall a very fine print of one of the most famous photos ever made, Adams' "Moonrise," and compared to prints of more or less the same size that come out of my m4/3 cameras printed on a Canon printer, it's not notably sharp. No way it could be, given all the manipulations that Adams put the negative through. But it's not lifeless, and you'd go a long way to to find a photograph that you could call "better."
As almost everybody knows, Adams and other people who advocated straight photography called themselves "Group f64." But f64 was diffraction limited even on 8x10 cameras, which would suggest something about how much they worried about it. Again, IMHO.
Deciding about trade-offs between maximum image quality and achieving the desired image that meets or exceed the requirements of the desired outcome (what others may refer as good enough) is perfectly valid.
Just ignoring the trade-offs because you think that science is BS or that your camera is not subject to the laws of physics does not makes sense to me.
| f/5.6 in focus | f/8 out of focus |
| (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-5.jpg) | (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-12.jpg) |
| f/5.6 in focus | f/16 in focus | f/8 out of focus | f/16 out of focus |
| (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-5.jpg) | (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-17.jpg) | (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-12.jpg) | (http://echophoto.dnsalias.net/ekr/images/DoF2/A55_100Macro_small1-20.jpg) |
No one is saying science science is BS. Science indicates there is diffraction, it doesn’t make a value judgement on the importance of diffraction, you do that. You are saying diffraction is more important than depth of field. That is not science, that is your value judgement. Saying that people that don’t agree with your value judgement are unscientific is very poor reasoning indeed. Try at least to understand the arguments from the other side.
It’s like this. There is a trade off between something appearing out of focus due to shallow depth of field and something appearing to be soft due to diffraction. It can happen that a photographer decides he needs deep depth of field and for various reasons focus stacking is not an option. If the need for deep depth of field is greater than the need for micro detail then you stop down and the hell with diffraction. Perhaps the image doesn’t have much micro detail or perhaps the micro detail is unimportant or less important in this instance, whatever. It is a creative decision. It’s not saying I don’t believe in diffraction, it is a decision that it is less important in this instance.
If most people and the photographic community in general agreed with this whole concept of least diffraction above all else lenses would come Limited to around f5,6 and we would simply use shutter speed and iso to control exposure.
It would have been interesting to learn, had Adams had the possibility of focus-stacking like we do today, what he would have done ...
Thank all for the feedback and examples. Thanks especially to Erik for spending the time to respond with much wisdom. So for those of us that will continue capturing at f11 - f22, what is the best way to apply deconvolution sharpening? Is this accomplished with Adobe Lightroom? What about Focus Magic? And no I"m not suggesting that it cures the effects of diffraction. I'm interested in fine art printing.
Thank all for the feedback and examples. Thanks especially to Erik for spending the time to respond with much wisdom. So for those of us that will continue capturing at f11 - f22, what is the best way to apply deconvolution sharpening? Is this accomplished with Adobe Lightroom? What about Focus Magic? And no I"m not suggesting that it cures the effects of diffraction. I'm interested in fine art printing.
FocusMagic remains to be a very useful and robust tool.
The implementation in ACR is of lower quality, but some use a very low amount and a high 'Detail' setting.
Like Martin, I use Capture One Pro as Raw converter, and it has a built-in option to correct for diffraction, and it is quite effective.
Cheers,
Bart
Ah, the battle of masterbators vs. measurbators! Or photographers vs. engineers ;)C’mon Slobodan: anyone who bothers to use a camera with way more resolution than “normal” printing and viewing requires (more than about 12 MP?) needs to understand all the factors that might affect image sharpness; otherwise they risk being seen as money-wasting dilettantes. In the high resolution realm, thinking about how aperture affects diffraction (or as I call it, “the pinhole camera effect”) and thus sharpness is no more esoteric, irrelevant or “geeky” than thinking about how aperture choice affects DOF or how shutter speed affects motion blur.
C’mon Slobodan...
Ah, the battle of masterbators vs. measurbators! Or photographers vs. engineers ;)