#WHAT IS CUTOFF FREQUENCY FULL#

In contrast, the Canon 5D Mark II, a 21.1mp Full Frame sensor, has a diffraction limit of f/10.3. My Canon 450D, a 12.2mp APS-C sensor, has a diffraction limit of f/8.4. In a color bayer sensor, where a square junction of 4 photosites will be capturing an alternating pattern of GRGB colors, as airy disk can affect the final color rendered by those four photosites as well as cause softening or improper resolution. In a black and white sensor or foveon sensor (stacked color sensels), that would only cause softening. It is entirely plausible for an airy disk to be focused at the border between two photosites, or the junction of four photosites. It is also possible, and likely that point light sources will NOT be perfectly focused onto the center of a photosite. The 'diffraction limit' of such a sensor would be higher (say f/16) than for a sensor that is able to distinctly resolve both point light sources (which might be diffraction limited at f/8). In this case, even if two highly resolved point light sources generate airy disks that merge over a single photosite, the end result will be the same.the sensor will only detect a single point light regardless of the aperture. This is the case when airy disks focused by a lens cover only a fraction of a photosite. It should be noted that it is possible for a lens to resolve a smaller spot the pixels in an imaging medium. This is the diffraction cutoff frequency. The point at which the center of each airy disk merges is the limit of resolution, and you will no longer be able to resolve any finer detail regardless of the aperture used. This is the point where a sensor is 'diffraction limited', since individual point light sources no longer resolve to a single photosite.they are merging and covering more than one photosite. When the aperture is stopped down, the airy disk generated by each point light source grows, to the point where the outer rings of each airy disk begin to merge. At a wide aperture, two point light sources imaged by a sensor may only affect single neighboring photosites. Another way to look at it is when the airy disks from two point light sources resolvable by the sensor begin to merge. The diffraction limit is the point where airy disks grow large enough that they begin to affect more than a single photosite. When the airy disk grows in size and intensity as a lens is stopped down, the airy disk affects neighboring photosites. This is due to the fact that a smaller photosite covers less of the airy disk area than a larger photosite.

A sensor with smaller photosites, or film with smaller grain, will have a lower limit of diffraction than those with larger photosites/grains. The 'limit' of diffraction is a function of the imaging medium. As noted above, lenses are always creating a diffraction pattern, only the degree and extent of that pattern changes as the lens is stopped down.

It should also be clearly noted that the diffraction limit is not actually a limitation of a lens. You realize that every one of those points of light, when focused by your lens, is generating its own airy disk on the imaging medium. The size of the airy disk, and the proportion of the disk that comprises the outer rings, and the amplitude of each wave in the outer rings, increases as the aperture is stopped down (the physical aperture gets smaller.) When you approach photography in the way Whuber mentioned in his answer: First, diffraction always happens, at every aperture, as light bends around the edges of the diaphragm and creates an ' Airy Disk'. There have been some very good answers, however there are a couple details that have not been mentioned.

What is cutoff frequency