Asobinet posted this accurate size comparison between the new Sigma 24-70mm FE, the Panasonic 24-70mm f/2.8 and Panasonic 24-105mm f/4.0 zooms.
Petapixel tested all the best 24-70mm lenses and comes to the conclusion that the Panasonic L lens is the best performer. Still they recommend the also very good Sigma 24-70mm lens because of the much lower price:
Though the Lumix was most commonly my personal favorite out of each of the tests, I don’t know that I would say it’s the best purchase. If you recall, initially I said this was a test of sharpness vs price, and the Lumix is nearly twice as expensive as the Sigma.
Is the Lumix twice as good as the Sigma? That’s ultimately up to you to decide, but I personally don’t think it is. It’s definitely better, and I think if money were no issue I would select it over the field. But since money is always an issue, it’s hard to argue against the Sigma.
DxOmark tested the Leica SL 35mm f/2.0 lens and concluded:
Many professionals and high-end amateurs consider the 35mm focal length to be an alternative to the 50mm, and as a result, require models with similar or even better optical quality. However, as lens sizes have increased over the years to offer superior image quality, there remains a need for smaller, lighter lenses that offer similar image quality.
Leica’s APO-Summicron-SL series appears to offer just that, and its smaller, lighter f/2 lenses are as well or better corrected than “standard” f/1.4 versions. With such an exotic optical construction, then, the Leica APO-Summicron-SL 35mm F2 ASPH has many attractive qualities, including good sharpness starting at f/2, low LCA, and almost no distortion. It’s also almost as bright as some f/1.8 lenses. All of this comes at price, though, and the $4595 ticket isn’t for the faint-hearted.