09-25-2011, 11:49 PM
[quote name='Brightcolours' timestamp='1316987234' post='11852']
My point being that if you get diffraction related resolution loss with a 5D mk II with a pixel/sensel pitch of 6.4µm, there is no way Nikon 1 10mp with 3.2µm would start having diffraction related resolution loss at f11, which I believe is what you stated above somewhere?
The diffraction limit for such a sensor will be below f4.
My other ultra micro Nikkor (28mm f1.8) can achieve 650 lines or more aerial resolving power at e-line (546.1 nm wave length) for a 4mm image circle, so it is basically diffraction limited already at f2.8 (f2.8 is limited by diffraction for e-line at 536 lines). <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/blink.gif' class='bbc_emoticon' alt=':blink:' />
[/quote]
Sorry, BC, but lens diffraction limits are entirely aperture related, nothing else. And sensor diffraction limits are Nyquist frequency, and Airy disk radius related, with the latter being diffraction realted. Read the article on diffraction limits on the site I quoted earlier, and you'll see what I mean.
The diffraction limit for a lens at F/1.8 is 1600/1.8 = 888 lp/mm, and at F/2.8 it is 571 lp/mm. If the resolution the lens achieves is lower than the diffraction limit, it is NOT diffraction limited. The only thing that diffraction limited means, is that the lens resolution surpasses or equals the diffraction limit, and that at the aperture from where it is diffraction limited, it cannot resolve more than the diffraction limit, even if it would be capable of resolving more. And when a lens becomes diffraction limited, it stays so from that aperture on, for all smaller apertures as well IOW. The better a lens is, resolution wise anyway, the larger the aperture is at which it is diffraction limited, and this is not to be confused with sensor diffraction limits.
In short, if this lens does not achieve a resolution of 888 lp/mm at F/1.8 it is lens limited (or aberration limited) at that aperture, not diffraction limited. Having said so, 650 lp/mm at F/1.8 is extremely good.
As mentioned world class photographic lenses are generally diffraction limited at F/4, where they achieve 400 lp/mm in aerial images, and this is not because they possibly couldn't resolve more by themselves, but because this is all that diffraction allows for it to resolve. And lesser lenses are only diffraction limited at smaller apertures, hence at lower resolution. Their resolution is not as high as that of world class lenses. The smaller the aperture at which a lens is diffraction limited, the more lens limited it is, and hence the less actual lens resolution it has.
As to sensor diffraction limits, the lens diffraction limit doesn't come into this, not straight away anyway. The diffraction limit aperture wise of a sensor (or film for that matter) is NR=N = 3.2 * pixel spacing or final grain size (µm), IOW, for a 3.4 µm pixel pitch it is F/11. And for the 5D II it is F/20 (3.2 * 6.4). This is the aperture, at which the lens resolution is less or equal due to the aperture diffraction limit to the diffraction limit of the sensor (which is determined by the size of the radius of two adjacent Airy disks which can still be resolved as two different ones). Do note that the resolution in lp/mm of the Nikon V1/J1 sensor is much higher than that of the 5D II, exactly because the pixel pitch of the former is smaller. It is only 10 MP, however, hence has much less total resolution information (apart from DR, SNR etc.), and also requires much larger magnification than the image from a 5D II for it to be printed as a print of the same size.
Kind regards, Wim
My point being that if you get diffraction related resolution loss with a 5D mk II with a pixel/sensel pitch of 6.4µm, there is no way Nikon 1 10mp with 3.2µm would start having diffraction related resolution loss at f11, which I believe is what you stated above somewhere?
The diffraction limit for such a sensor will be below f4.
My other ultra micro Nikkor (28mm f1.8) can achieve 650 lines or more aerial resolving power at e-line (546.1 nm wave length) for a 4mm image circle, so it is basically diffraction limited already at f2.8 (f2.8 is limited by diffraction for e-line at 536 lines). <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/blink.gif' class='bbc_emoticon' alt=':blink:' />
[/quote]
Sorry, BC, but lens diffraction limits are entirely aperture related, nothing else. And sensor diffraction limits are Nyquist frequency, and Airy disk radius related, with the latter being diffraction realted. Read the article on diffraction limits on the site I quoted earlier, and you'll see what I mean.
The diffraction limit for a lens at F/1.8 is 1600/1.8 = 888 lp/mm, and at F/2.8 it is 571 lp/mm. If the resolution the lens achieves is lower than the diffraction limit, it is NOT diffraction limited. The only thing that diffraction limited means, is that the lens resolution surpasses or equals the diffraction limit, and that at the aperture from where it is diffraction limited, it cannot resolve more than the diffraction limit, even if it would be capable of resolving more. And when a lens becomes diffraction limited, it stays so from that aperture on, for all smaller apertures as well IOW. The better a lens is, resolution wise anyway, the larger the aperture is at which it is diffraction limited, and this is not to be confused with sensor diffraction limits.
In short, if this lens does not achieve a resolution of 888 lp/mm at F/1.8 it is lens limited (or aberration limited) at that aperture, not diffraction limited. Having said so, 650 lp/mm at F/1.8 is extremely good.
As mentioned world class photographic lenses are generally diffraction limited at F/4, where they achieve 400 lp/mm in aerial images, and this is not because they possibly couldn't resolve more by themselves, but because this is all that diffraction allows for it to resolve. And lesser lenses are only diffraction limited at smaller apertures, hence at lower resolution. Their resolution is not as high as that of world class lenses. The smaller the aperture at which a lens is diffraction limited, the more lens limited it is, and hence the less actual lens resolution it has.
As to sensor diffraction limits, the lens diffraction limit doesn't come into this, not straight away anyway. The diffraction limit aperture wise of a sensor (or film for that matter) is NR=N = 3.2 * pixel spacing or final grain size (µm), IOW, for a 3.4 µm pixel pitch it is F/11. And for the 5D II it is F/20 (3.2 * 6.4). This is the aperture, at which the lens resolution is less or equal due to the aperture diffraction limit to the diffraction limit of the sensor (which is determined by the size of the radius of two adjacent Airy disks which can still be resolved as two different ones). Do note that the resolution in lp/mm of the Nikon V1/J1 sensor is much higher than that of the 5D II, exactly because the pixel pitch of the former is smaller. It is only 10 MP, however, hence has much less total resolution information (apart from DR, SNR etc.), and also requires much larger magnification than the image from a 5D II for it to be printed as a print of the same size.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....