Are sensors outresolving lenses? Keep reading

Battle of the 50mm lenses: the contestants

Every time sensor resolutions go up the thing people keep asking the most in comments and forums is: will the latest Sony, Sony or Sony* sensor out-resolve our lenses?

* Sorry folks, Canon and Nikon haven’t come out with a sensor of their own in ages

And every time someone pops out saying that “12 / 24 / 36 / _insert_value_here megapixels are too much for current lenses, we need better ones”.

Guess what? Someone, other than DXO, has been working on the matter. The people at lenscore.org use a custom made 200Mp sensor (yes, I can see you drooling… 😉 ) to test the average resolving power of many current lenses, alongside many other aspects like flare resistance, contrast, bokeh. I am not affiliated with them in any way, and my understanding is that they are indeed strictly non-commercial; besides, they claim to buy on their own the lenses they test, so these are not cherry-picked by the manufacturers.

They test sensors as well, at the twin site of senscore.org, but now we are talking about lenses.

I don’t know exactly what their procedure is, much like in the case of DXO, but for the bit of explanation they give at their website “FAQ” section it does look pretty sound.

Based on their inquiries, they found that one of the best lenses tested, the Zeiss Apo Distagon 55mm f/1.4 Otus, can deliver at its best performing aperture (f/3.7) around 100 megapixels of sweet resolving power. Yes, I did not add a zero by mistake: that’s a hundredth, 100, one-zero-zero megapixels. That’s more then enough to disturb the dreams of every photographer I know.

In their own words:

“Let’s have a closer look at our current number 1, the Zeiss Apo Distagon T* 1.4/55 Otus. Maximum resolving power is just a little bit under 100MP at an aperture of f/3.7”

What did you say? Why I wrote “one of the best lenses” and not “the best lens tested”?

Because, amazingly, the 55 Otus ranks just 4th – yes, fourth – in terms of pure resolving power, bested by both the Leica wonder twins Apo Summicron 50/2 and Summilux Asph 50mm f/1.4 and by the absolute king, its even bigger brother: the Zeiss Apo Planar 85mm f/1.4 Otus. By the way, having that kind of spare change laying around, I would take an Apo Summicron or Summilux every day over one of those two gigantic Zeiss beasts…

Stream rapids in a gorge

The people at lenscore.org do not explicitly report – like DXO does – how much resolution a lens has in terms of megapixels, they use instead a home-made rating system. But they say that:

“It’s safe to say that most current f/2.8 and f/4.0 constant aperture zoom lenses and almost all current f/1.4 and f/1.8 primes would – to some degree – profit from a 54MP sensor.[…]In conclusion, one can say that full frame sensors are still far from outresolving high grade lenses. Based on our measurements, the reasonable maximum resolution for full frame sensors is probably somewhere around 100MP”.

What is interesting is that with some fairly basic math, now that we have a threshold (the 100Mp resolved by the Otus), we can estimate how much megapixels the other lenses tested can resolve.

I made such back-of-the-envelope calculation with some of the lenses I know better or I am interested in (some of them just in my dreams, unfortunately…), and these are the results:

LensLenscore ratingMegapixels
Zeiss Apo-Planar T* 85/1.4 Otus1,647107
Leica M Apo-Summicron Asph 50/21,622106
Leica M Summilux Asph 50/1.41,578103
Zeiss Apo Distagon T* 55/1.4 Otus1,532100
Leica M Elmarit Asph 28/2.896663
Leica M Summicron 50/291460
Canon EF L Usm 135/282754
Zeiss Planar T* 85/1.480152
Zeiss Planar T* 50/1.478751
Zeiss C-Sonnar 50/1.569545
Canon EF 50/1.8 II62841

It really looks this time we might be approaching the upper limit in terms of useful sensor resolution, at least for lenses made for mere mortals; but at the same time this shows that there is still a long way to go if we are prepared to / can afford to spend a pretty penny.