Monday, October 18, 2021

Sharper than Sharp

A phrase I'd heard and had found myself repeating uncritically was that regarding high-megapixel camera sensors "out-resolving" the lenses that were on them. It came to mind again recently when I saw stuff like this.

That Six-Four Impala was shot with a 36MP Nikon D800 using a mid-'90s vintage Nikon 35-105mm f/3.5-4.5 AF-D lens. At first glance, it looks okay, but blow up to full screen or (worse) start pixel peeping at 100% magnification and something' The lines of the car have a bit of blur to them, especially the chrome ones. It doesn't have the knife-edged *pop* I'm used to from the D700 or D3. That effect was visible in most all the photos I took on that excursion.

To make sure it wasn't my imagination, this past weekend I put the lens on the D700, with its 12MP full-frame sensor.

We're back to almost cartoonish sharpness on the lower-resolution sensor. Both shots are 1/320th at f/9. Clearly the D800 has enough resolution for glass to really matter. 

From Thom Hogan's original D800 review:
But this will be an eye-opener for some of you. Resolution not only reveals more detail, it can also reveal more about how your lens performs. A lot was written about how the D800 would out-resolve lenses. Get that out of your mind, because that's not what's happening. Your lenses are capable of resolving even more than the D800 models will manage. But along with that extra resolution comes the ability to actually resolve what the lenses are doing. Poor corners become very obviously poor. Edge to edge sharpness differences (miscentered elements, etc.) become more obvious, especially on a D800E at or near maximum aperture. Chromatic aberrations now encompass more pixels on edges, so often become more visible at pixel level, too. Be prepared to see how your lens actually performs, at least if you're a pixel peeper or printing big.

As it turns out, that list that Nikon had in their Technical Guide for the D800 turns out to be basically right: the modern zooms (f/2.8, f/4 max apertures), most of the recent fast primes (f/1.4, f/1.8), the Micro-Nikkors, the PC-E lenses, and the exotic telephotos (200mm f/2, 300mm f/2.8, etc.) are all very good on a D800 model. Used with discipline and given a bit of post processing clean-up, they can be stunning.

Drop down to the next level of Nikkors--the 28-300mm f/3.5-5.6 comes to mind--and the results aren't quite so stunning. Heck, that lens is diffraction impacted above about 135mm, even shooting wide open, so this really shouldn't surprise anyone. That doesn't mean I wouldn't use that lens on a D800 model, only that my expectations would be that I won't get as much out of the camera as I would with even the 24-120mm f/4 in the overlapping focal lengths. Lenses that you can stop down to hit f/4 tend to do even better, such as the f/2.8 zoom trio.