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As a lens property, sharpness is affected by resolution (the ability to clearly resolve alternating black and white lines) and acutance (the ability to resolve such lines with high contrast; see here for a excellent tutorial on this and many other phenomena).  Prior to the popularization of CCD and CMOS technologies, inquiries into sharpness were limited to lens performance.  One could certainly opt for a film emulsion with finer grain (e.g., Velvia 50), but the relative invariance of emulsion used by a given photographer meant that sharpness was largely considered a sole property of the lens.  This “primitive” state of technology nonetheless provided plenty of image quality issues to consider:  spherical aberrations (longitudinal and lateral), chromatic aberrations, coma, curvature of field, astigmatism, barrel and pincushion distortions, and vignetting.

With the advent of digital photography, and the ostensible megapixel war among the major manufacturers, we are now faced with prospects of pixel peeping.  I can honestly say that I never gave much consideration to the limits of diffraction on image quality before moving to digital.  I was aware that one ought not to shoot 35mm film with an aperture much slower than f/16 or f/22, but the apparent difference in most slides or prints between this and faster apertures seemed somehow less than crucial, especially when attempting to maximize depth of field for a landscape shot.

Now, with the ability to view my 12MP digital shots at 200% or even 400%, I can clearly discern the limits of sharpness imposed on the sensor by diffraction (cf. the recent debate elsewhere regarding the relative merits of the Canon 7D’s 18MP sensor).  Does this imply that my work, which today is arguably far better than it was when I began shooting nature photography 7 years ago, is somehow inferior in sharpness to my original work shot with Velvia?  I think not.

I realize that some photographers will disagree with the following contention, but I suspect we have become overly enamored with the importance of sharpness in photography.  It is clear that digital sensor technology allows us to perceive the limits of diffraction like never before.  Perhaps what is now necessary is a reevaluation of whether a slightly “soft” photo is somehow inferior to one that has been sharpened in post-production.  I seek sharpness, just like anyone else.  At the end of the day, however, the most important thing to me is whether I make the shot.

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  1. […] lot about matters related to image quality; I am especially intrigued by diffraction (see here and especially here for my previous relevant comments).  Diffraction seems to be a big deal these days among […]

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