Remote Light Sensitive trigger for digital SLR

I am interested in starting a project in which I control the shutter of a camera with a photoresistor. I have been researching how to do so, but am unsure about which would be the best method.

I want to place an object on top of a photo resistor, and when the object is lifted and light is exposed to the resistor, the shutter fires. The most logical way of doing this seems to be hacking a remote for my Nikon D80 to the circuit and having this control the shutter. So far, I have found information about how to create a trip wire with a photo resistor and laser pointer, but not with only the photo resistor.

Any ideas or advice for me? I'm new to Arduino and need help!

Since all you want is a single shutter press signal you might be able to record it and play it back with the Arduino controlling a IR LED. See the IR Remote Library:

Using an analog input you can just look for a change in resistance of the CDS cell. The value will change with the amount of light. If you check once a second and trigger on ant change of more than, say, 10, you don't even need to care if the value goes up or down.