FZ200 Diffraction Limit - Panasonic Tech Service

Started Aug 27, 2013 | Discussions thread
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J C Brown Senior Member • Posts: 1,559
Re: FZ200 Diffraction Limit - For Ron tolmie

Ron Tolmie wrote:

Panasonic's lens designers would be aghast to hear what Panasonic's "tech" staff are claiming.

All lenses are subject to diffraction at all f/ stops - it doesn't "begin" at any f/ stop. There may be some other factor that is more damaging to the performance of the lens - optical design faults or sensor problems, for example, so lenses/cameras differ with respect to what settings are optimal, but the diffraction contributions (more than just resolution is affected) are simply determined by the physical diameter of the diaphragm. That assumes that the resolution is measured in arc sec, not lines per mm.

The FZ200 has an aperture diameter of only 1.6 mm at its shortest focal length and maximum aperture. The consequence is that its resolution degradation attributable to diffraction is substantially worse than, say, that of the LX7. At its maximum focal length the maximum aperture diameter is 38.6 mm for the FZ200. Since the diffraction is inversely proportional to the diameter the diffraction effects are much less significant at long focal lengths. Optical aberrations are usually the limiting factor at the long focal lengths of lenses that have big zoom ratios.

Although the FZ200 has an unusually large f/ stop (and aperture diameter) at its longest focal length the advantage that confers to the resolution is quite small so other cameras that typically have smaller apertures at their maximum focal length may be just as sharp. The large f/ stop is of course very desirable because it permits faster shutter speeds and lower ISO settings.


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Ron Tolmie

Hi Ron,

Ron Tolmie / 3mm minimum sensor size

As you haven't yet replied to Sherm's original post or any of the subsequent responses it seems that you may have missed the above thread.

For my own benefit and that of other forum members who may be interested I would be very grateful if you could provide a more detailed explanation of the origin of the "3mm" aperture and its relation to the F/No, which as I understand it is simply the focal length of the equivalent single element lens divided by its effective aperture.

Thanks in advance


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J C Brown

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