Can I use the Nikkor 35mm f1.8 lens on a D700?

Currently, I have a DX camera (Nikon D70s). I have the Nikkor 35mm f1.8 DX lens and I want to purchase the D700 in the near future. I heard that the D700 will switch to a 5mp when using DX lenses. Is this true? Also, what will happen if I use the 35mm lens in FX mode on the D700?

Yes, you can use that 35mm f/1.8 lens on the Nikon D700. The camera will automatically switch to DX format with that lens; the largest image that it can record in DX format is 2, 784 x 1, 848 or about 5.14 megapixels. If you were to use any DX lens in FX format, you would end up with circular vignetting that takes up approximately 1/3 of the frame because the lens is designed for cameras with smaller DX sensors.

Yes, but you'll be stuck with 5MP photos. It doesn't seem like you know enough about photography to warrant the purchase of a D700. I suggest you buy either a D5100 or D7000.

A D700 will switch to DX mode (you can download manuals before you plunk down $1800 on a high end camera) which is low resolution or you'll get a distinc vignetting effect.

If you like 35mm I'd sell the 1.8 and get a used f2 version. It's fx and will work well on your D70s. Difference optically is marginal.