Too sharp lenses?

Started 1 month ago | Discussions thread
fPrime
fPrime Senior Member • Posts: 2,822
Modern full frame lenses are indeed too sharp
5

Here's a different tack than the one taken by the OP, but hear me out.

I do think modern full frame lens design has drifted too far towards optimizing sharpness over price/weight and other lens rendering qualities. Compared to what, you ask? Well, just a decade ago we had DSLR's with 6-12MP resolution that worked great with modestly-sized (and priced) lenses like Nikon's AF-D series of primes.

But Canikony basically couldn't innovate cameras beyond adding more resolution so now we have full frame resolutions that fall between 24-50MP. Previously this sort of resolution belonged primarily to medium format. The problem is that in order to squeeze this much resolution into full frame, Canikony had to optimize their full frame lenses for sharpness over all other considerations.

Lens design is basically an exercise in trade-offs. Although a lens can be created with as few as two or three elements, its optical aberrations are likely to be high and its corners wide open will be soft. To correct a sufficient number of aberrations for older DSLR's, older primes typically used 6-9 elements depending on focal length. This led to compact, lightweight designs that were inexpensive as well.

Designing lenses optimized for high resolution full frame sensors, however, requires more corrected optics which increase sharpness by reducing aberrations. Additional elements are needed to reduce aberrations, bring corners into better focus when shooting wide open, and to better blur the OOF background. Typical modern primes consequently use 12-15 elements. All of this additional glass adds to the monster weight, size, and cost of these lenses.

Unfortunately many modern lenses also pay a price in rendering compared to their older predecessors. This is because the more glass there is in the barrel, the more the light is degraded before it hits the sensor. Low-level tonal resolution, otherwise known as microcontrast, is one of the first casualties. Without being able to transmit as much microcontrast, many modern lenses can render images that look decidedly clinical, sterile, and flatter.

Here is where I find some older lenses are still better... because of their simpler designs many of them still render more microcontrast and 3D Pop than modern glass. Lens sharpness is a good thing, but to prioritize it over microcontrast is a crime. To balance the two would obviously limit full frame resolution to its 12MP sweet spot, however, and I can just hear people arguing that would be a crime.

Yet, this is when I would counter that high resolution imaging be left to medium format. There the larger sensor format allows for more balanced lens designs as sharpness need not be driven as hard as it is being currently being driven in full frame. Unfortunately people want to have their pie and eat it too. So here we sit with 50MP full frame DSLR's and monster lenses that render very "digitally" compared to a decade ago.

fPrime

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