through the viewfinder (ttv) is a really easy technique involving two cameras: a digital camera and an antique TLR (twin lens reflex) camera. essentially, you are composing the shot with the TLR and shooting with the digital.
you will need to use a longish lens hood to keep light from entering the top of the viewfinder on the TLR. I use a shipping tube cut to about 6-8". paint it black (flat black spray paint) if you are getting light reflections or flares. I attach the mailing tube to my stock lens hood with black duct tape.
it also helps to have a macro lens attachment (I use a cheap screw on one.) try out different strengths; half the fun of ttv is working out the kinks and idiosyncasies. what it will give you is a lovely dreamy look. blurry at the edges, slightly distorted with one sweet point of focus.
in the next post i will show how people are doing faux ttv in photoshop. super easy, but not as cool looking (in my opinion.)