Gloves + Mittens = "Glomitts"
My wife and I made up that name. I have no idea what they are really called. Wait, I found them; EMS calls them "Convertible Mittens." How boring. I'm going to continue calling the "Glomitts" and encourage you to do the same.
Here they are:
If you look at the thumb you'll see the thumb "hoodie" ("thudie"?) pulled back. It's held in place by a magnet embedded in the fleece. There's a similar finger hoodie ("foodie"? Nah, that doesn't work at all) on the backside of this shot. The magnets are apparently attracting cat hairs. That's my story and I'm sticking to it.
The Jedi mind trick is to put on the finger hoodie but keep the index finger exposed, like so:
Thus configured, there are only two fingertips exposed to the freezing cold while the other three fingers snuggle and talk about how nice it is to be off duty for a change. Here's the glomitt in photog mode:
That's real simulated outdoor cold-weather shooting you're seeing here. Actually, it's the kitchen. But with the two fingertips free, you can control the camera easily. Your left hand can be completely mitted or completely fingerless gloved or anywhere in between as you see fit.
The glomitts worked great in Philly at the New Year's Day Mummer's Parade. Here they are at EMS. Warning, do not throw into the dryer on high heat. Don't ask how I know this.