Summary: Larger sensors can achieve higher resolution than smaller ones only if they have more photosites. To date, the potential of full-frame sensors, in terms of image resolution, has been limited by the fact that FF sensors typically have relatively large photosites. A 36 MP FF sensor has 4.9 µm photosites, and a linear resolution of about 7,400 photosites on its long axis (3:2 aspect ratio). On the other hand, a 20 MP 1-inch sensor has 2.4 µm photosites, and a linear resolution of about 5,500 photosites on the long axis. The 35% increase in resolution provided by the FF sensor is much less than the actual difference in linear dimensions of the sensors — 172%. In order to exploit the full potential of larger sensors with respect to image resolution, it will be necessary to keep photosites small. That will involve some sacrifices in low-light performance, and entail costs in processing very large (> 100 MP) images. Also, in order to fully realize the benefits of photosite spacing of 2 – 3 µm, lenses must perform exceptionally well at f/2.8 – f/4: perhaps close to the theoretical limits set by diffraction. Assuming such FF lenses can be manufactured at reasonable cost, use of such relatively large apertures will compromise the ability to obtain appreciable depth of field while at the same time realizing increased resolution.
Key Words: sensor size, image resolution, sensor pixel size, photosite size, line-pairs, equivalent cameras, equivalence