How to measure the Intensity of Light?

[ZapperZ]

As long as they know the QE, they can do a calibration. They question is how do they know ~50 QE?

What does this have anything to do with my post?

Note that you were claiming that ALL photons can be detected by such devices (i.e. PMT). This is what I was arguing against. Being able to detect single photon is NOT the same thing as being able to detect ALL photons.

Zz.

 

[Andy Resnick]

As long as they know the QE, they can do a calibration. They question is how do they know ~50 QE?

I guess they could down convert one photon into two using a non-linear crystal? Then they would for sure know they have two? I'll admit, it's not a very straight forward method.


I was just throwing this idea out there. I don't know how they really measure light intensity either. That's what I'm trying to figure out. I'm still looking through equipment on the web. I'll post again when I find an intensity measurement whose calibration is straight forward.

Who is 'they'? NIST? Random scientists and engineers? Photographers? There's a large number of ways to measure intensity.