Fraunhofer Lines: Outdoor Photo Through Bandpass Filter

[pyroartist]

If you take an outdoor photo through a bandpass filter that only let's light through in a Fraunhofer line would it be completely dark, like night? Or would it have some daytime illumination?

 

[rumborak]

In theory it would be dark yes. However, what comes in at those lines is never entirely zero, and you will never have a filter that only exactly filters that line.

 

[pyroartist]

OK, thanks. I also see that such narrow band filters are prohibitively expensive for the average experimenter.