Trippy stuff - this is MTF data from nine copies of the Canon EF 16-35mm F2.8L II, at 16mm. Nice and sharp in the center, less so at the edges. That said, all nine of these lenses test as 'good' samples. 

Arch lens nerd Roger Cicala has probably handled more lenses this week than an average photographer might use in a lifetime. And recently, he's been busy testing multiple copies of several popular wideangle zooms to try and prove what he calls 'Roger’s Law of Wide Zoom Relativity'.

Simply stated, Roger's 'law' states that wideangle zoom lenses are virtually always sharpest at the wide end of their zoom range, softening as the lens is zoomed. Although many of us have often wondered whether this is the case, Roger's exhaustive testing proves that it holds true over multiple copies of several modern lens designs, all the way from Nikon's 14-24mm F2.8 to Canon's stunning new 16-35mm F2.8L III.

Averaged MFT charts for nine copies of Nikon's 24-70mm F2.8VR on the left, and data from the older 27-70mm F2.8 on the right. Advances in lens design are obvious from increased sharpness and better consistency across the zoom range. 

What does this mean for the average enthusiast photographer? Just that if you're the kind of shopper that obsessively tests and returns lenses which aren't up to your requirements (cough, cough - Rishi...) you can save a lot of time by only testing the long end. 

Also of interest is just how good some modern lens designs are. Compared to its predecessor, the new Canon 16-35mm F2.8L III's MTF charts are extraordinary. Likewise Nikon's 24-70mm F2.8 VR, compared to the lens it replaced.

Thanks as always, Roger, for testing nine copies of everything so that we don't have to.

Read Roger Cicala's full blog post at