What are ‘L standards’? Are they the same today as several years ago?
TL;DR – I really recommend people stop worrying about lenses needing digital correction of distortion. It's a non-issue from an output standpoint, and yields some meaningful benefits in that lenses can be smaller, lighter and cheaper.
Have a look at these three uncorrected RAW images (left; post-correction in DxO PhotoLab is on the right). They seem to fit your description applied to consumer-grade black lenses of ‘black corners with tons of correction’ needed.
View attachment 217263
The lenses are (top to bottom) the RF 10-20mm f/4L at 10mm (Al Capone's cell in the Eastern State Penitentiary), the RF 14-35/4L at 14mm (Fontana dei Quattro Fiumi in Piazza Navona, Rome), and the RF 24-105mm f/2.8L at 24mm (a local cemetery taken the first day I got the lens). All of those lenses are black, but none are consumer-grade (the last one being a $3000 lens).
It might be worth considering that the definition of L quality has changed and now includes appropriate post-processing of images when required. Yes, the black corners result from compromises in the optical design, shifting the burden of some of the image correction from the glass in the lens to the processor downstream from the sensor. There is no reason optical correction is inherently better than digital correction, despite the issue some people have with the latter.
In the case of the above lenses, the trade-offs are evident and beneficial. The RF 10-20/4 is
significantly smaller and lighter than the EF 11-24/4 that it effectively replaces (I used to own the latter), and it's also significantly cheaper. The RF 14-35/4 delivers a 2mm wider FoV compared to the EF 16-35/4 it replaces, and does so while keeping the same 77mm filter size. The RF 24-105/2.8 would almost certainly be much larger, heavier and more expensive as a more optically-corrected EF lens.
When I
compared the RF 14-35/4 at 14mm to the EF 11-24/4 at 14mm, I found that the RF lens after DxO's profile to correct the 'black corners with tons of correction’ delivered the FoV of approximately 13.5mm and was just as sharp in the corners as the bigger, heavier, costlier EF lens. For that test, the deck was stacked in favor of the EF 11-24, since the lens transitions from strong barrel distortion to pincushion distortion right at 13-14mm, i.e. that's the point in the zoom range where the lens needs basically no correction of geometric distortion. Yet the corrected RF 14-35/4 delivered similar IQ in the extreme corners.
There's no such thing as 'optical purity'. Any rectilinear lens must have the distortion corrected, either using more glass in the lens or digitally after the image is captured. The proof, as they say, is in the pudding. If the digital correction can yield a smaller, lighter, cheaper lens that delivers the same image quality output, personally I think that's awesome.
