You asked
Nikon d610 vs nikon d810?
The Nikon D610 is the cheaper way into full frame. It has a 24.3-megapixel sensor and was announced in 2013, so it's a good pick if you want full frame without spending much. The Nikon D810 (announced 2014) has a 36.3-megapixel sensor, which gives you more room to crop and print large. I'd call it still a strong used body for landscape work.
Both use the Nikon F mount and have no in-body stabilisation, so use stabilised lenses for slow shutter speeds. For landscapes on either body, the Nikon AF-S 14-24mm f/2.8G ED is a wide, sharp choice. For everyday shooting, the Nikon AF-S 24-70mm f/2.8E ED VR covers a lot of ground. If you want a fast portrait lens, try the Nikon AF-S 85mm f/1.8G.
Check the Nikon D610 and Nikon D810 pages for the full lens lists.
Written by Claude from this site's pages.