Nikon d810 vs sony alpha a7r2,which one's a better option for my next dslr camera?

Hi
should i go with the sony a7r2 and skip the d810 as my next dslr camera or should i stick with the d810 btw i already have a tamron 24-70 2.8g vr lens for my d810 which originally i purchased for my d7200 (which i sold )and i don't have any other lens with me currently to use with the sony a7r2 and my budget is only 2 lakh rupees that is 3000 $

The A7 isn't a DSLR, and if you don't know that, you should stick with what you have.

The a7R2 is not a dSLR so that leaves you with the D810.

What I love about the D810 is ISO 32 plus that optical viewfinder. What makes me consider the a7R2 in this battle is low light ability. I'm not saying the D810 isn't good in low light. It's full frame and it does great however, I like what Sony has to offer better. Truth be told, if I could afford both, I go for both - the D810 for shooting under the sun and the a7R2 for low light.

The Nikon is likely to be more robust and do better on batteries.
The Sony perhaps if you do a lot of studio work.

You will not be able to use your existing Nikon-mount Tamron lens on a Sony body.

I would go with the Sony because ever since the D800 came out, the ones that came out after that were pretty much the same camera, too many megapixels. There's no need for that many.

Based on the wording of your question, the D810 would be THE only option since it's the only DSLR between the two cameras that you've listed.

Personally, I'd go with the A7R2 since the D810 has some known, uh hem, reliability issues. Plus you can use any lens with the Sony vs only Nikon lenses with the D810. On the other hand, if you're doing a lot of fast action, you would likely get more usable shots with the D810 than the A7R2.

If you are shooting a lot of low light work, then definitely go with the Sony A7R2 over anything from Nikon. The Sony has in-body image stabilization while Nikon has VR which is their in-lens solution. The problem with VR is that it requires additional lens elements. This will degrade the image qualtiy as has been widely complained about with the Nikon 24-70. You pay $600 more the 24-70 with VR and it's noticeably less sharp than the cheaper 24-70 without VR. Plus the lens is heavier, too. This is where Sony just kills Canon and Nikon. With in-body stabilization, you can use any lens and since the sensor is doing the stabilizing and not additional lens elements, you won't have any loss of optical performance, you won't be paying more and getting less, and you will get a stabilization system that works on all 5 axis instead of just 3 with VR. The Sony will allow you to get shots in low light that are simply not possible with a Nikon.

If you want to do video, then definitely avoid Nikon and go with the much more advanced A7R2. Nikons are just atrocious for video, while Sony is among the best.

So depending upon what you do, I would say go with the D810 if you only do sports, and go with the A7R2 if do anything else.

I've never been one to jump on new fads and new gimmicks; it's just my nature to wait until the dust settles and see the innovations and improvements take place, until the fad is tried and proven AND if I have a need for it.

As I've pointed out before, mirrorless cameras are the new "toy" now pushed on the public. Question: is there really any significant improvement in the quality of images that result form a mirrorless camera? I only hear people complain about the battery drain they find with mirrorless cameras; how is that an "improvement" and "advantage"? Oh, yes, they're slightly more compact and weigh slightly less… That's not my priority for purchasing a camera… I'm more interested in the camera's quality output and the quality images I can get, and the variety availability and costs of future lens purchases. If I want a compact camera, then I'll buy a pocket-size camera compact camera. But that's just ME, and not necessarily a law written in stone. (Nikon offers over 70 lenses available on the market for Nikon cameras; how many lenses are there on the market for Sony A7R2?)

I'm a full frame Nikon user (heck, my full Internet moniker is Kalico (or Calico) the Nikonian) and rather than buying the most expensive camera with all the bells and whistles, I only buy what I need and what I can use. Why would I want something with features, functions and options I don't need or can't use? That's simply unnecessary baggage that comes at a cost to my cobwebbed pockets. Why did I choose full frame? In order to use my film camera lenses (I had seven but gave 2 away to my little gorgeous, talented niece).

It's up to you to make a wise and better informed decision.