Tweet
Re: Is your camera diffraction limited? If so, why?
It's hard to compare diffraction softness and focus blur without looking at examples back to back. I would think they would be quite similar apart from one thing -diffraction softness affects everything equally in the frame whereas focus blur will be distance-dependent.
In the 'old' days it was obligatory to stop a lens down to get the best optical resolution, but that's not the case any more. Lens designers now know that their designs need to perform wide open, partially because maximum apertures are often smaller (darker) than they used to be - many of us would have a 50mm f/1.8 standard lens when we used film, but use of these is quite rare now, so we use zooms with maximum apertures ranging from f/2.8-6.3, typically. There is less latitude for stopping down because of brightness alone and for some of us the spectre of diffraction also comes into it. Take the new 16MP Olympus OM-D E-M5; its kit zoom has a maximum aperture of f/6.3 at the long end (50mm or 100mm FF equivalent). That's almost on the diffraction threshold for a 16MP Four Thirds sensor. Thankfully diffraction comes in gradually, so in normal circumstances you can dip below the threshold, but for more critical work you would need to rely on the lens working at its best wide open.
Let me see if I can find some time today to provide some examples to post here.
Ian
It's hard to compare diffraction softness and focus blur without looking at examples back to back. I would think they would be quite similar apart from one thing -diffraction softness affects everything equally in the frame whereas focus blur will be distance-dependent.
In the 'old' days it was obligatory to stop a lens down to get the best optical resolution, but that's not the case any more. Lens designers now know that their designs need to perform wide open, partially because maximum apertures are often smaller (darker) than they used to be - many of us would have a 50mm f/1.8 standard lens when we used film, but use of these is quite rare now, so we use zooms with maximum apertures ranging from f/2.8-6.3, typically. There is less latitude for stopping down because of brightness alone and for some of us the spectre of diffraction also comes into it. Take the new 16MP Olympus OM-D E-M5; its kit zoom has a maximum aperture of f/6.3 at the long end (50mm or 100mm FF equivalent). That's almost on the diffraction threshold for a 16MP Four Thirds sensor. Thankfully diffraction comes in gradually, so in normal circumstances you can dip below the threshold, but for more critical work you would need to rely on the lens working at its best wide open.
Let me see if I can find some time today to provide some examples to post here.
Ian
A 12MP Four Thirds DSLR as a third of the the resolution of a D800 in a quarter of the sensor area, so not that far off the pixel pitch of the D800 - slightly more densely populated but not by a lot, so the results should be useful. The Zuiko Digital 50mm f/2 is a tremendously sharp lens, so ideal for the job.
Comment