So what’s an MB-D18? To use Nikon nomenclature, it’s the “multi-power battery pack” for the D850 camera. It’s the add-on grip that lets the D850 hit 9 frames/second (versus the 7 fps the camera alone tops out at). Well, 9 fps if you also add a battery from a D4 or D5 camera and the special BL-5 battery chamber cover needed to mount that battery into the MB-D18. Of course you’ll also need a charger for that battery. Wowza — this adds about $1000 out of pocket to get two more frames per second. So is it worth the expense?
The answer is simple and is the same exact answer I give to all photographic questions: it all depends.
Let me stop right here and make one statement: if I could only have one camera right now to photograph landscapes and wildlife and everything else, my choice would be a D850. Is it a great landscape camera? The best I’ve ever used. Is it a great wildlife camera? While it’s a good wildlife camera, I do think the D5 is a better choice for someone who is a wildlife specialist. But like I said, if I could only have one camera, then give me a D850.
So back to the MB-D18. Adding it does make shooting vertical compositions a lot easier, but at the same time it bulks up the size of the camera quite a bit. Plus the total weight of the camera increases a lot depending on which “multi-power” source you use. Two battery trays come standard with the MB-D18, one for an additional EN-EL 15 battery (the same as used in the camera body itself), and one for eight AAs. Neither of these change the frame rate; the camera still tops out at the default 7 fps. You’re simple adding additional power time to the camera. In my opinion you can just leave that AA tray in the box. But you should have an extra EN-EL 15 battery no matter what, and adding the second one in the grip really extends shooting time.
Landscape photographers certainly don’t need a faster frame rate, but having an additional battery in place, along with the one in the camera body, might help occasionally. I can think of several scenarios: extended time lapse shooting, hours of star trail photography, and severe cold weather work. I was in Jasper National Park in February when it was minus 30° F. It was difficult enough at that temperature to change a lens let alone a camera battery. As a side note, the D850 worked perfectly at 30 below, no problems. My own ability to function, or even semi-function, was the problem.
It’s that 9 fps option that really adds expense, so the nitty gritty question is whether you really need 9 fps or not. When photographing wildlife every frame counts, so the answer might be “yes” if wildlife plays an important part in your photographic plans. So, yes, I did purchase an MB-D18 along with a BL-5 battery cover. But then I already have a D5, an extra EN-EL 18a battery for the D5, and the D5 charger, so the additional expense was not as much as it might have been. Here’s a little money saving story: I like having a second charger to leave in the camper I have on my truck, but the $370 for another MH-26a (the charger that comes with the D5) put me off. A couple of quick phone calls to dealers and I found a used MH-26 (the charger that originally came with the D4 bodies) for a whopping $44. Now that’s more like it.
So, do you really need 9 fps? If so, go for it. If not, take that $1000 you saved and spend it on a photo trip.