About Diffraction on m4/3s

Started Sep 19, 2012 | Discussions thread
Sanpaku
Forum MemberPosts: 62
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Re: Or a more general rule of thumb (for more formats)...
In reply to Paul De Bra, Sep 21, 2012

I recommend the following article for a good discussion of diffraction limited photography:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

It's only the interaction of Airy disk size (determined by lens f-stop) and pixel size that creates diffraction limits, not the sensor dimensions, per se.

Examples using the calculator at that site:

The (rather old) 135 format full frame Nikon D2H has 4.11 megapixels, and a pixel size (pitch) of 14.5 µm. It isn't diffraction limited until after f/22.

The (state of the art) 135 format full frame Nikon D800 has 36.56 megapixels, and a pixel size of 4.9 µm. It is diffraction limited between f/8 and f/11.

That's not to say that the D800 doesn't resolve much better than the D2H between f/11 and f/22. Only that at f/11 and above, it is diffraction effects that limit maximum effective resolving power to below the 36 megapixels on the sensor. By f/32, I suspect like the D2H it also has an effective resolution below 4 megapixels.

In the Micro 4/3s format, 12 megapixel cameras have a 4.3 µm pixel size and are diffraction limited after f/8, but 16 megapixel cameras have a pixel size of 3.7 µm and are already diffraction limited just before f/8.

While there are advantages to having higher megapixel sensors in resolving power at wide apertures and in resistance to moire and noise (if downsampled), I think physics are dictating an end of the megapixel wars, within at most one more resolution doubling.

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