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Thread: pixel pitch, Airy disk diameter and maximum aperture

  1. #1
    darekk's Avatar
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    pixel pitch, Airy disk diameter and maximum aperture

    Hi,
    How to determine a threshold aperture, at which the diffraction begins to limit resolution of the sensor ? Which situation reflects that point:

    1) Airy disk diameter / 2 = 2 x pixel pitch
    http://www.outbackphoto.com/dp_essen..._02/essay.html
    (third pixel detects the dark gap between two points)

    2) Airy disk diameter / 2 = 1 x pixel pitch

    3) Airy disk diameter = pixel pitch
    it seems that Wikipedia, and many webpages

    #1 and #2 just meet the Rayleigh criterion of resolution, #3 is far further.

    pixel pitch, Airy disk diameter and maximum aperture
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    Last edited by darekk; 22nd July 2011 at 10:47 PM.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Your first post? Congratulations and welcome to CiC! Most of us update our profile with at least our first name to be more friendly in the threads.

    It looks interesting, Darekk, but I haven't a clue as to what it means. Sorry.

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    darekk's Avatar
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    Re: pixel pitch, Airy disk diameter and maximum aperture

    It means
    2 * P = D / 2 or
    P = D / 2 or
    P = D
    for maximum aperture ?
    where
    D – Airy disk diameter
    P – pixel pitch

    Another question is - which pixel pitch to choose:

    pixel pitch, Airy disk diameter and maximum aperture

    horizontal/vertical (blue Airy disks), diagonal (red Airy disks) or average ? This would depend probably additionaly on shape of pixels.
    And maximum aperture value should be called rather optimal aperture value.
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    Last edited by darekk; 23rd July 2011 at 10:12 PM.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    I am told that many pixels go to waste after a certain number, as no one can print and look at all thoses pixels so close?

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Hey this is such a cool question; I don't know the answer but eagerly await one. I just use what I'm told as true but it is always preferable to be able to justify why you do something. For instance; I would use f6.4 maximum because manufacturers say my camera is f7.1 red diffraction limited, but it is much better to be able to work out why for yourself.

    Looking forward to an answer

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by wlou View Post
    I am told that many pixels go to waste after a certain number, as no one can print and look at all thoses pixels so close?
    Hi Louise,

    Personally, I think the mega-pixel "war" should have been declared a draw once they flew past the 8 to 12MP range. Basically, the bigger a print, the further away people look at it, and thus the less detail our eyes are able to see in it - and thus the maximum number of pixels that are of use to us is relatively constant (with the exception being photographers, whose minimum viewing distance is limited only by the length of their noses!). Prints displayed online usually have approx 95% (or more) of the pixels removed so that you don't need a monitor 35 to 50 inches wide to be able to see them at full resolution.

    So in other words, just don't worry about it -- there's a LOT more to photography than taking photos of test targets and looking at them at 100%.

    Here's a good example. This photo was shot at F20; do you see a horrible diffraction-limited photo, or a nice photo of a lovely girl? (that looked just fine printed 22 x 15 on canvas too).

    pixel pitch, Airy disk diameter and maximum aperture

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Sometimes I wish we could go back to the good old days of film when photographers rarely if ever printed their pictures larger than a postcard. Some used slide film and projected it on a nice big screen but then sat six foot away so unless you had Supermans eyes you couldn't tell if it was really sharp or not.

    Digital photography has created a weird obsession with pixel level sharpness and ISO related noise that takes over people's lives and ruins the real point of a photography - that is to go out, enjoy your hobby, take some pictures and show them to others so they can relive the scene in a way that you as the 'artist' wanted to portray it. If the picture truly does that then the emotional connection will override any technical issues.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Hello Colin, I agree with you, le final result is what counts. For some, the technical aspect is all they can talk about. It is not such a bad thing when those people are the ones that come up with a new design for a super camera, the designer count for what, 0.01 per cent of the population,hehe.(I just love throwing numbers around).
    I did not realise that so many pixels did not make it to the net! And yes, most of us will rarely print, and the image format are relatively small.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Hello Robin, in the good old days, did they not have something called "film grain". Something that was considered a quality in a print when well executed? Could it be that the technical aspect is killing the art in what is a representation of the world around us as seen throught the eyes of the photograph. Does the price you have paid for the camera supersides the result: quality of execution, choice of interesting subject, color of a particular light, emotion the viewer experience like in the picture above. When the viewer goes WOW, am sure it is the result of an emotion more than a technical calculation. This does not negate the great techniques that may have been used, just that all the aspect add up to a final product that may be classified as Art.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by black pearl View Post
    Sometimes I wish we could go back to the good old days of film when photographers rarely if ever printed their pictures larger than a postcard. Some used slide film and projected it on a nice big screen but then sat six foot away so unless you had Supermans eyes you couldn't tell if it was really sharp or not.

    Digital photography has created a weird obsession with pixel level sharpness and ISO related noise that takes over people's lives and ruins the real point of a photography - that is to go out, enjoy your hobby, take some pictures and show them to others so they can relive the scene in a way that you as the 'artist' wanted to portray it. If the picture truly does that then the emotional connection will override any technical issues.
    Photography is everything, not a little bit of this and a little bit of that. Some people put lenses costing thousands on a cheap body, then use software costing thousands but say, a little bit of noise isn't a bother.
    I see the photographers job as capturing as much information about a scene as possible, then preserving or getting the best out of the information before being artistic: Of course s/he had to compose it closely, but first see it, but then the mission becomes getting as much information out of the zone as possible.
    I had some pictures of my grandaughter printed a long time ago before I even knew about noise, one was very noisy on a small print, it had pattern noise because I didn't pay enough attention to exposure, and I didn't give that one away but framed it and stuck it on my wall to remind me of a complete waste of money it is to not pay attention to everything.

  11. #11
    rob marshall

    Re: pixel pitch, Airy disk diameter and maximum aperture

    Phew!

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by arith View Post
    Photography is everything, not a little bit of this and a little bit of that. Some people put lenses costing thousands on a cheap body, then use software costing thousands but say, a little bit of noise isn't a bother.
    I see the photographers job as capturing as much information about a scene as possible, then preserving or getting the best out of the information before being artistic: Of course s/he had to compose it closely, but first see it, but then the mission becomes getting as much information out of the zone as possible.
    I had some pictures of my grandaughter printed a long time ago before I even knew about noise, one was very noisy on a small print, it had pattern noise because I didn't pay enough attention to exposure, and I didn't give that one away but framed it and stuck it on my wall to remind me of a complete waste of money it is to not pay attention to everything.
    We'll have to agree to disagree here I'm afraid because personally the last thing I look for in a photograph is the actual up close quality.

    Some of the greatest photographs on earth by some of the greatest photographers on earth were taken on basic (by todays standard - rubbish) equipment. I can think of several that aren't sharp, several that have no shadow or highlight detail, some that are grainy beyond belief and some that if taken today on a DSLR would likely have been deleted immediately after being checked on the rear screen.

    But.......they have such emotional grab, perfect timing and the shear, utter brilliance of capturing a moment in time that everything else is immaterial.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by wlou View Post
    I did not realise that so many pixels did not make it to the net! And yes, most of us will rarely print, and the image format are relatively small.
    Hi Louise,

    As a case in point, lets look at my photo above. If you click on it you'll get the biggest version - which is 1200 x 800 pixels - and I hope we agree that it's probably bigger than most photos you'll see on the net - and also I hope we can agree that one probably doesn't usually need anything bigger than that. It was shot with a 21MP camera, and currently only has 960,000 pixels - so by my maths, it only has 4.6% of the information of the original file. If that had been taken with an 8MP camera, it would still have only used 12% of the original data ... and yet many7 people will still prefer "Camera A" over "Camera B" because "Camera A" has 18MP and "Camera B" only has 16MP.

    Kinda reminds me of the old nuclear weapons race where "Country A" is better than "Country B" because they have enough nukes to kill everyone in the world 7 times over, whereas "Country B" can only kill everyone 4 times over!

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    http://diglloyd.com/articles/Diffrac...ple-1DsM3.html

    I think a 1Ds is probably quite superior to my amateur camera, but still. Did I say artistic temperament was not important; no. It is the most important but not the only thing.

    What is wrong after seeing an image; to capture it as best you can.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Well, if this is 4.6% of the information on the original, I cannot "see" what the fuss is about?

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by wlou View Post
    Well, if this is 4.6% of the information on the original, I cannot "see" what the fuss is about?
    Me neither

    Folks get FAR FAR FAR too caught up in "specifications" (obviously encouraged by manufacturers), when in reality, it often doesn't make a lot of difference. I've got a new 1Dx on order, and for me the BIG features will be better high ISO performance so that when my ISO & aperture are maxed out I can get above 1/20th to 1/80th to stop motion blur, and smarter AF etc

  17. #17
    rob marshall

    Re: pixel pitch, Airy disk diameter and maximum aperture

    Quote Originally Posted by black pearl View Post
    Some of the greatest photographs on earth by some of the greatest photographers on earth were taken on basic (by todays standard - rubbish) equipment. I can think of several that aren't sharp, several that have no shadow or highlight detail, some that are grainy beyond belief and some that if taken today on a DSLR would likely have been deleted immediately after being checked on the rear screen.
    You mean like this one? This was a developing error, but I agree with what you say. http://www.worldsfamousphotos.com/in...y-france-1944/

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    Can someone please explain the original question in words I can understand? It's been doing my head in for an hour!

    Another question is - which pixel pitch to choose:
    ???


    What possible relevance can this have to my understanding of photography?

    I wouldn't ask but I'm thick.

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    I got nearly all my knowledge on diffraction from CiC, and is endorsed here by someone who appears to know his stuff:

    If you’d like to read more about diffraction from a technical perspective, there is an approachable explanation at cambridgecolour.com which discusses diffraction in the context of depth of field. A depth of field calculator is provided.
    We think it’s a waste of time to bother with a depth of field calculator, which calculates based on ideal lenses, which don’t exist. Calculations can be misleading to anyone but experts; real-world factors intrude and make the calculation non-actionable when actual photos are taken with real lenses. Reasons for this include varying performance across the image area, curvature of field, astigmatism, spherical aberration, color aberrations, and the critical loss of contrast due to diffraction and other factors. Not to mention focus error in placing the ideal plane of focus. Know thine own lens(es), lest ye be misled!
    I don't think I need to know the answer to the original posters question to take a good picture, but I still would like to know.


    http://diglloyd.com/articles/Diffrac...n-example.html

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    Re: pixel pitch, Airy disk diameter and maximum aperture

    I've got a new 1Dx on order, and for me the BIG features will be better high ISO performance so that when my ISO & aperture are maxed out I can get above 1/20th to 1/80th to stop motion blur, and smarter AF etc
    Really?

    Nothing to do with it being new, expensive and having a Canon badge on then.......now then, when are Nikon going to announce that D4.

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