In which ways, and why, are smaller sensors more efficient than larger?

Started Feb 19, 2014 | Discussions thread
OP Anders W Forum Pro • Posts: 21,468
"Executive summary"

Some people have asked for an "executive summary" of the OP of this thread. Here it is.

Executive summary

According to the principles of equivalence, a camera with a larger sensor can shoot any image just as well as a smaller-sensor camera under the provision that the sensors are equally efficient. But are they?

In a prior thread on the PST (photographic science and technology forum) I showed that smaller sensors tend be more efficient than larger. It follows that smaller sensor cameras can produce images with higher signal-noise performance when the more shallow DoF of which the larger-sensor camera is capable is not desirable or acceptable.

However, in a recent thread on the MFT forum, it was argued that the difference in efficiency applies only to one of the two quantities that affect the signal-noise performance of the sensor (read noise), not the other (quantum efficiency), and that the difference with regard to read noise at higher ISOs is largely explained by the fact that larger sensors tend to have more pixels than smaller (so that there is no such difference once the pixel count is held constant).

In the OP of the present thread, I report the results of some additional analyses performed in order to test the validity of these two claims. The results indicate that the first claim is not correct. There are systematic efficiency differences between larger and smaller sensors not only with regard to read noise but also with regard to quantum efficiency. The results also suggest that the second claim might not be the whole story although they do not reject the idea that the pixel count is one of the factors that might mediate the effect of sensor size on read noise at higher ISOs.

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