Return 12-35 varo x for sigma 18-35?

[Brian Caldwell]

Actually, the Sigma 18-35 f/1.8 plus a Speed Booster XL becomes an 11.5-22.4mm f/1.1, as indicated by Aaron.  If you wrapped black tape around the barrel of the combination and sent it as a "mystery lens" to Abel or Zeiss to measure the focal length and f/# using their fancy bench tools they would report back 11.5-22.4mm f/1.1 (plus moderate tolerances).  If you compared it directly to a 12-35mm f/2.8, it would be wider at the short end, with less zoom range and much larger aperture.  

[jonpais]

 

right, Brian, I was thinking of full-frame equivalent.

[jonpais]

Actually, the Sigma 18-35 f/1.8 lens + Metabones Speed Booster XL 0.64, whether it is a 1/2 stop slower or whatever than stated, is a spectacular combination that allows me to get shots I could never have gotten with the Panasonic Vario 12-35mm f/2.8, and, if anything, is even sharper than the Panasonic lens. The color rendition is also beautiful. It is already razor sharp at f/1.1 and improves a bit when stopped down to f/2 or so. If anything, the pairing is already almost too sharp for shooting faces, even with the sharpness setting turned all the way down. I don't regret spending $1,500 for the Sigma and Metabones, and wonder how the new ULTRA 0.71 could possibly better this. Since most GH4 owners are looking for an adapter that reduces the crop factor, I wouldn't hesitate a second to recommend the XL over the ULTRA version.