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The Nikon D70 does not have a black-and-white mode setting.

However, you can take your photo in color and then use software to convert it to a grayscale photo. (Black and white implies an image with only those two values per pixel; grayscale can have 8 to 16 bits per pixel.) Most photo editing packages have a "desaturate" feature that does an automated conversion to grayscale.

The open source image editor Gimp has a "channel mixer" dialog that would allow you to approximate the effect of various filters before performing the desaturate function. This would allow you to experiment with the procedures if you do not have a commercial photo editor like Adobe PhotoShop. There is a special wrapper of Gimp that puts its interface into a configuration like that of PhotoShop; look for "GimpShop". The open source image manipulation package ImageMagick may also be used if you prefer working with command line utilities.