Wednesday, May 6, 2009

My own rebuttal

Some months ago I wrote about the differences of the APS-C sensor format and full-frame. Despite the fundamentals of all the arguments I presented in favor of the smaller format (smaller lens sizes and weight, same expected resolution and the benefit of Moore's law), I found one sustainable argument in favor of the full-frame sensor supremacy.

The arguments deals with the fact that for all things equivalent (same resolution, etc.) each individual pixel on the sensor is of a smaller size on the smaller sensor. In other words, each pixel on a 12-Megapixel APS-C sensor is smaller than each pixel on a 12-Megapixel Full-Frame sensor.

The first issue -which I addressed on my previous entry- is the amount of light that falls on the sensor. A bigger pixel gathers more light than a smaller one, so if Signal-to-Noise ratio is an issue the full frame sensor performs better, but in the case of a better technology where noise is reduced significantly and the material in itself is more sensitive, this becomes a non-issue.

One another effect is related to the imperfections on the lens surface that determine the sharpness of the lens. A smaller sensor captures images created by a smaller section of glass on the lens. It is presumable then that acceptable sharpness calls for more precisely crafted lenses when utilizing very small sensors. This is a purely optical issue.

At this time, I have not seen a good calculation of when this effect becomes noticeable, but initially it seems to be that a full frame sensor would be more tolerant to less-than-perfect lenses and would be capable of rendering sharper images.

My problem with this is that it can be a self-fulfilling prophecy since the leading camera and lens manufacturers make more high-quality lenses for full-frame (or legacy 35mm) cameras. In other words, better lenses are only made in the format that does not require them that much!

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