GoofyNewfie Loc: Kansas City

I recently sold an an older 85mm here for a friend.
Tried it out before I shipped it and was sorry I didn’t buy it for myself.
Compared to my 70-200, I loved the size, lack of weight and faster aperture.
Reminded me of why it was in my bag back in my newspaper days when I didn’t have a zoom.
I’ve never liked the perspective a 50 gives me.
Don’t own a prime in that length, other than the 55 micro Nikkor, which I use for close-ups.

cahale Loc: San Angelo, TX

In the new "selfie" world, no one would care if you took them with an old Brownie. If you have small rooms, and expect to shoot many inside, 50. If otherwise, 85.

yorkiebyte Loc: Scottsdale, AZ/Bandon by the Sea, OR

.... I need some Boxes.... What's the name of the store?!?

larryepage Loc: North Texas area

I have a D850 and "last generation" versions of both of these lenses. Either or both of them will prove to be very useful for you. BUT...in my experience, 85mm is a little bit long when taking photographs of family gatherings in most homes...you just don't have room to back up far enough for the group shots. In fact, I was at a family party Saturday evening when 24mm wasn't wide enough for a shot of the whole group on a crop frame camera. If I'd had my D850, it would have been plenty.

Please don't let the arguments around "why buy either when you have the 24-70" talk you out of buying a either lens. There is real benefit in your situation in having a smaller, more nimble setup. And with family gatherings, there is generally not any problem around getting a little closer anyway.

There is, of course, a real benefit from using an 85mm lens for more serious portraits, since it will produce inages with more attractive facial features. But you aren't likely to have the space to use it in your gatherings, so my inclination would be to get the 50mm lens now and flag the 85mm for "next." Truth is that there isn't a huge difference between 70mm and 85mm. For now, you could use the zoom if any "serious" opportunities arise.

Have fun, whichever way you decide to go.

wdross Loc: Castle Rock, Colorado

Yours is a dilemma. More detail in the group shots or more detail in the portraits? I would go for the 85mm. Your group shots will be best with the eventual purchase of the 50mm. But to get a good single person portrait, you need a longer lense than 50mm. With group shots, there will be more than enough detail from your zoom lens for now. A head and shoulder portrait with a 50mm just looks too distorted compared to a head and shoulder portrait done with an 85mm. And the 85mm will provide more portrait detail than the zoom set to the same focal length. And people are more accepting to the slightly less detail in a group shot than they are in a portrait.

ELNikkor

A 1.8 50 can take great portraits as well as group shots. An 85 would be mostly restricted to portraits. Get the 50 first, later on, if you feel the need, get the 85. (You don't need a 1.4 anything!)

queencitysanta Loc: Charlotte, North Carolina

24-70 and 70-200 All you need

queencitysanta Loc: Charlotte, North Carolina

24-70 and 70-200 All you need

Tjohn Loc: Inverness, FL formerly Arivaca, AZ

The 85 is ideal for photographing children being children in their day to day adventures while NOT posing. It is also good for portraits as it doesn't distort features, thus making the subject look more normal. Wider than 50mm emphasis the closer features. Really wide and you can get a great big nose in front of a small face. Fun, it that is what you want.

Kmgw9v Loc: Miami, Florida

The 50 and 85 are great prime lenses that I own and use.
But, for what the the OP describes, the 24-70 is first lens to acquire.
It is the lens for indoor family events.
Then, the 70-200.

dpullum Loc: Tampa Florida

When Kodak was king the recommended 85 for portraits. If you buy only one lens, then the 85 sense it gives some reach. 50mm is the standard that was on all old film fixed lens cameras it is a workhorse so to speak.

The Nikon D850 is full frame so 50mm is 50mm etc... no multiplier as in smaller sensors.

Fotomacher Loc: Toronto

If you have those two zooms and they are f/2.8, then you don’t NEED a 50mm or a 85mm. That said, the 50mm is more versatile. If you want superior results that will max the sensor in your D850, look at the Sigma ART 50mm f/1.4. I may sell my Nikkor 50mm f/1.4 to get the Sigma.

larryepage Loc: North Texas area

I'll have to disagree a little bit here. In addition to the wider aperture, f1.4 lenses tend to be superior both physically and optically to their "equivalent" f1.8 brethren. I've owned both in the past, and found the bigger lens much better in terms of color fidelity, overall sharpness, and <especially> corner sharpness. Construction, operation, and overall "field" were also much superior in the f1.4 lens, which was designed and manufactured to much higher standards.

Notorious T.O.D. Loc: Harrisburg, North Carolina

Between 50 and 85 I would take the 85...

genocolo Loc: Vail and Gasparilla Island

Having five grandchildren ages 3-12 and having tried over the years to get some goods shots of them, I have found a good zoom much more helpful than a prime.