'But I am still not seeing an example of a photo which shows that a sensor outresolves any kind of lens attached to the camera.'
But first, 'it is also true that vintage lenses have lower contrast' is not something you can be categorical about, and vintage refers to what years of release? Even if you use 10lpmm as a surrogate for 'lens contrast', which is fair enough, my CY 21/2.8 recorded around 97% on this measure - wide open. It's a 1993 lens, 31 years old.
The lenses I chose in the above post were not random choices, but all share the same design characteristics of very consistent cross-frame performance. The CV 35/2 loses 12% at best aperture from centre to corner. The 100MP loses 11%, and the venerable zoom loses 20% to the corner, and just 11% to the wide edge.
These figures correspond closely with Leica's latest two 35mm APOs (M and SL) but at reduced MTF levels, around 15-18% lower. The exception being the CV 35/2 APO, which is on parity with the M/SL lenses. (all MTF here = 40lpmm, unless stated otherwise.)
To finish, when Sony first released the a7r, many photographers rushed to see how their older lenses performed on this new versatile camera that enabled all manner of lenses to be used via adapters on its 36mp sensor. They were astonished to observe the dramatic change in these (not so wonderful) old film lenses that looked pretty decent on film prints. What happened? The outers were now progressively horrible, and the centres were amazing.
As an example, you would not need to look at say, Leica's Summilux-R80/1.4 on a high res camera at f5.6, because it loses 60% from near-axis to outer frames - with inevitable results!
The reason was the multiplicative relationship between sensor resolution and lens resolution, expressed across the image's real estate. We found that high res cameras heavily punish lenses with poor outer frames/corners while boosting the axial region disproportionately. It's the reason modern lenses have relatively flat MTF lines, designers realised they needed to fix the residual aberrations that were concentrated in outer frames, but had gone unnoticed in film and the early transition to low Mp digital.
So when we travel from the image backwards, the issue of 'out-resolving' matters recedes into abstract chat; and it matters much less than the perennial need for sound lens design and (I suspect) sensor Mp - lens performance harmony. But no one did that experiment, did they?
Finally, to support my contention see this graphic display of what happens to lens outer frame performance when transitioning to a 50mp sensor from a 21mp sensor, on a new Canon lens:
The bottom line is that lens design turns out to be very important to high resolution cameras, slip up and the images will look very different - caveat emptor! I think the actual cross-frame profile of output images is the secret 'third dimension' to the arguments surrounding 'resolving'. The devil is in the detail here. You need much more that 'this outresolves that'. Much more.
Jul 17, 2024 at 08:44 PM
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