Diffraction is the problem
18/08/09 10:11 Filed in: Education
DIFFRACTION IS THE PROBLEM
by
David Magahy
At what point do you get the sharpest possible image from the kit you currently own or are contemplating purchasing in the foreseeable future? Is more pixels the answer? Or is it a more expensive lens?
I have been following a debate on these matters on the Luminous Landscape website for some weeks. Originally Ray Maxwell wrote an essay entitled “Why Moore’s Law does not apply to Digital Photography”
In this essay he postulates that we may be soon reaching the limit of pixel growth within the confines of the 35mm format. He suggests that 100 megapixels is not only unlikely but unnecessary anyway.
Diffraction caused by the glass in the lens appears to be a major issue, and grows as a problem as the megapixels increase. As owners of the new 20 Megapixel plus cameras may be finding, there are already signs of things being slightly different than before.
I should add straight away that there are a couple of follow on essays rebutting the findings of Maxwell and they seem to become ever more complex in their explanations, especially of the Physics involved.
What I am getting from these articles is that as the megapixels rise, then the lens sweet spot falls. In other words, conventional wisdom stated that a correctly focussed image around an aperture of f11 will give you the sharpest possible result for your landscapes, with maximum detail in the fore, middle and background at the hyperfocal distance of your scene. Now, if I am understanding these essays correctly, it would appear that my Canon 5D Mk II for example, will give me a sharper image at around f8 than at f11, and that as we move to 50 Megapixel that might drop to f5.6 and 100 Megapixel might be f4.
It appears that technically it is possible to make 100 Megapixel sensors sometime in the future, but to cure the diffraction issues may prove impossible, thereby negating the advantages of a denser sensor.
If you want to really get into the arguments, then follow on from Ray Maxwells initial link above to the rebuttals
by
David Magahy
At what point do you get the sharpest possible image from the kit you currently own or are contemplating purchasing in the foreseeable future? Is more pixels the answer? Or is it a more expensive lens?
I have been following a debate on these matters on the Luminous Landscape website for some weeks. Originally Ray Maxwell wrote an essay entitled “Why Moore’s Law does not apply to Digital Photography”
In this essay he postulates that we may be soon reaching the limit of pixel growth within the confines of the 35mm format. He suggests that 100 megapixels is not only unlikely but unnecessary anyway.
Diffraction caused by the glass in the lens appears to be a major issue, and grows as a problem as the megapixels increase. As owners of the new 20 Megapixel plus cameras may be finding, there are already signs of things being slightly different than before.
I should add straight away that there are a couple of follow on essays rebutting the findings of Maxwell and they seem to become ever more complex in their explanations, especially of the Physics involved.
What I am getting from these articles is that as the megapixels rise, then the lens sweet spot falls. In other words, conventional wisdom stated that a correctly focussed image around an aperture of f11 will give you the sharpest possible result for your landscapes, with maximum detail in the fore, middle and background at the hyperfocal distance of your scene. Now, if I am understanding these essays correctly, it would appear that my Canon 5D Mk II for example, will give me a sharper image at around f8 than at f11, and that as we move to 50 Megapixel that might drop to f5.6 and 100 Megapixel might be f4.
It appears that technically it is possible to make 100 Megapixel sensors sometime in the future, but to cure the diffraction issues may prove impossible, thereby negating the advantages of a denser sensor.
If you want to really get into the arguments, then follow on from Ray Maxwells initial link above to the rebuttals
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