FZ200 Diffraction Limit - Panasonic Tech Service

Started Aug 27, 2013 | Discussions thread
Ron Tolmie Regular Member • Posts: 380
Re: FZ200 Diffraction Limit - For Ron tolmie


I had posted the equation for calculating the effect of diffraction in my original note. Most people assume that it is proportional to the f/ stop but it is not. It is simply (inversely) proportional to the diameter of the aperture. The tiny lens in a ZS20, the much bigger lens in a full frame camera, and the enormous lens in a big process camera will all suffer from the same resolution loss (in angular resolution terms) if they have the same aperture size, and in practical applications the smallest diameter that is capable of yielding really sharp images is about 3 mm for all of those lenses. Cameras (like the FZ200 and ZS20) that have smaller aperture diameters are not capable of producing what a critical photographer would consider to be a really sharp image at their shortest focal length. The same is true of an 800mm process camera lens that has been stopped down so that its diaphragm is under 3mm in diameter.

One of the interesting implications is that these small cameras could produce very sharp images at their longer focal length settings if the optical aberrations are very well controlled. At 100mm focal length an f/8 aperture corresponds to a 12.5mm aperture diameter, for which the diffraction effects are very small. That means that there is still room for substantial improvements in these tiny cameras if you are willing to live with softer images at the extreme WA setting. In that case the statistics for the number of photons captured per pixel tends to become the limiting factor for IQ.


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Ron Tolmie

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