FZ200 Diffraction Limit - Panasonic Tech Service

Started Aug 27, 2013 | Discussions thread
Ron Tolmie
Regular MemberPosts: 371
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Re: Diffraction Limit - A bit of revision.
In reply to J C Brown, Aug 29, 2013

Jerry:

What the equation states is that if you want to achieve a given angular resolution then there is a corresponding aperture dimension that will produce that resolution so long as some other factor (like optical aberrations) does not override the consideration.

Looking at it the other way around, if the aperture diameter is 3mm and the lens is intended to be used for imaging a "normal" field of view (equivalent to what you get with a 50mm lens on a full frame camera) then the image will be sharp, and it doesn't matter what the focal length of the lens is. You might have a different opinion on what constitutes a "sharp" image, but in that case the dimension might be a little bigger or a little smaller than 3mm, but the point is that there is a particular diameter that will satisfy your objective.

Cameras like the FZ200 and ZS20 have pushed the choice of sensor size right down to the point where diffraction is a critically important design consideration (although certainly not the only one!). They work well, especially if you apply some simple post processing. I printed up a batch of 11x14"  ZS20 prints this afternoon and they were sharp enough to satisfy me. However, I did not print any of the images that had used the longest telephoto settings because they were not sharp enough for my tastes.

I would argue that these cameras are operating right at the limit of what is practical. Examining the impact of diffraction is one of the most basic considerations that determine if they perform satisfactorily - or do we need to revert to using much larger sensors like M4/3 or full frame?

What the equation implies is that we really only need to make modest changes in the aperture size (and hence the camera size) to get away from the diffraction limitation. A really big sensor may offer other advantages, such as wider ISO settings and a wider choice of apertures, but I am happy to give up those advantages if it means that I can put a wide-zoom camera in my pocket.

Ron

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Ron Tolmie

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