These two photos show that the D70 sensor does not have a particularly strong IR filter over it. I photographed the bottom half of a black camera bag with my D70. This camera bag apparently reflects a good deal of IR light. The bag was illuminated by an incandecent bulb (strong IR source.) The camera's WB was set to incandescent. One the left edge of each photo is the edge of a neutral grey card for reference.

The first shot on the left is how the 'black' bag looks to my D70. It's not so black. It has a strong magenta cast. Notice the black strap is black. Some black fabrics reflect IR others don't. I wonder if this IR reflectance of the bag material is not an accident. It might keep the contents cooler on a bright hot day?

To my eyes there is a very slight magenta cast to the bag under this light, but its not anywhere near what the D70 reports.

Next I place a B+W IR cut filter on the lens and take the same shot with identical exposure. That photo is on the right. The black bag looks much closer to black. It appears in this photo much closer to what my eyes see.

The sub-gallery (candle_ir_test) contains photos of a test using a candle to investigate a question concerning IR and the light pillar artifact from the flame.