![]() Do worry about diffraction, but not in regard to the size of one pixel.Īnd for another thing (about any one-pixel notion), the digital sensor Bayer pattern is roughly areas of 3x3 sensor pixels to create any one RGB processed pixel, which is a complicated interpolation situation generally ignored concerning resolution.īut primarily (still ignoring Bayer), sampling theory "resolution" is instead determined in units of two pixels (Nyquist, et al.) A pixel is indeed the smallest dot possible, but resolution is expressed in "line pairs", a black line and a white line, which takes two pixels to show the difference. Yes, the diffraction is present, and is not zero, and is better without it, and diffraction can be a major issue, all true, but it is typically minor compared to Depth of Field issues for example. Diffraction is indeed serious, and can become pretty bad, but in smaller degree is often a smaller effect, the image detail is degraded, but still present, not quite sharp, but possibly hardly noticed. Instead diffraction everywhere causes a fuzzy lens, continuous blur that every pixel shares (if bright enough to be exposed). ![]() All Airy disks are overlapped by a few others, and there will be no visible Airy disks as such. But in any ordinary non-stellar consistently brighter regular pictorial photo typically with detail everywhere (except maybe blue sky), the diffraction is not just a few random spots scattered around. Acceptable diffraction Airy disk might be about the same size as the CoC limit, and bad diffraction Airy disk might be twice that CoC size. In our cameras, the Circle of Confusion (CoC) defining the maximum blur that defines a "sharp" image is typically 4 to 6 pixels size. Diffraction Airy disks are lens artifacts when optically magnified, around stars seen individually against a blank black background. The stars in a night sky are tiny infinitesimal "points", all much smaller than any pixel. ![]() Smaller pixels simply better resolve whatever detail is present, including the detail of diffraction. The concept of one pixel's involvement is ridiculous. If the lens is causing diffraction, there is continuous diffraction all over the frame, anywhere there is detail to resolve. Diffraction is not just one spot on a few pixels. It's about diffraction size.īut think further a second. Larger diffraction size obviously must affect additional pixels. Smaller pixels simply better resolve the detail that is present. It is very unlikely that each diffraction disk is somehow magically centered within one pixel, but the notion is that diffraction spreading outside of one pixel's area also affects the neighboring pixels, making things larger, worse. Of course the size of the pixels is a resolution limit, and that's there regardless of the presence of any diffraction. That's a fact, but far too simplistic regarding diffraction. That "one pixel limit" notion comes from the fact that the pixel is the smallest dot that digital sampling can reproduce (specifically, two adjacent pixels, a dark and a bright one, is the least difference that can be properly resolved as an edge). There's a calculator below.įirst, a rant about imagining the size of one pixel causes diffraction limiting: That absolutely does Not mean we need larger pixels, which would just be less resolution too. The problem is the diffraction size, regardless of the pixel size. And then yes, this Airy disk size can be computed in terms of our pixel's size, but which is just a comparison magnitude scale, and the pixel size as a measurement unit is NOT the problem. So we hear how our camera has an aperture limit, maybe a lens stopping down to near the lens f/stop limit, and that part is valid, stopping down the aperture does increase the diffraction. Then it covers and blurs the true detail, reducing resolution. Stopping down the aperture makes the diffraction become larger. Tiny pixels simply just better resolve any detail that is present, but pixels do not affect diffraction.Ī true point source when magnified (a star seen at high power in a telescope is a good example of diffraction) shows as a larger diffraction disk of concentric rings called an Airy disk ( see calculator below). It's not about the pixel, it's about the diffraction present. Yes, diffraction is a real problem caused by stopping down too much, but sometimes it is incorrectly worded in terms of the issue being when diffraction becomes larger than our digital sensor's pixel size. We read on the internet how our digital cameras can become "diffraction limited" as we stop down more.
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