What is the absolute sharpest, most clinical portrait lens available for the SL2 right now that can handle massive commercial prints? Ive been shooting with the SL system for ages, started with the original 601 and moved to the SL2 a couple years back, and usually the 24-90 Vario-Elmarit is my go-to for everything. It's a tank and usually sharp enough for my editorial work. But I just signed a contract for a big skincare campaign here in London next month and the art director is being super intense about micro-contrast and hyper-real skin texture. They're talking about huge 40x60 prints for the flagship stores.

I did some test shots with my zoom at the long end and it just felt... a bit soft? Maybe I'm just pixel peeping too hard or my copy is getting old but it isnt giving me that wow factor at f4 or f5.6 that I need for this specific job. I have a budget of about 5000 pounds to drop on a dedicated prime for this. I'm looking at the APO-Summicron-SL primes because everyone raves about the internal mapping and the corrected glass but I'm torn between the 75 and the 90.

• Is the 90mm APO actually sharper than the 75mm or is it just the compression difference?
• Does anyone have experience with the Sigma 85mm Art on this body? I know it's a fraction of the price but some people say it rivals the Leica glass for raw resolution.
• Should I even consider adapting an M-mount Noctilux or is that just gonna be a nightmare for focus accuracy on a fast-paced shoot?

I need something that is gonna be pin-sharp wide open because we're playing with some shallow depth of field but the focal point has to be absolutely surgical. My main worry is buying the 90mm and finding out the autofocus is too sluggish for a moving model, even if the glass is legendary. I usually pride myself on knowing my gear inside out but this specific maximum sharpness requirement is throwing me for a loop...