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Old 01-03-2013, 05:09 PM
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Peter Ward
Galaxy hitchhiking guide

Peter Ward is offline
 
Join Date: Dec 2007
Location: The Shire
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Quote:
Originally Posted by Shiraz View Post
Thanks for the response Greg.

There is no error. The number of detected photons (the signal) depends on the quantum efficiency and the number of photons actually entering the pixel -
Yes and no.

QE is purely a measure of how many photons are detected vs the total number of photons falling onto a pixel.

This is not the same as system sensitivity...which you correctly point out should take into account pixel size.

Given the current Sydney weather, the "bucket" analogy works well here.

Put a small cup outside in the rain for a time, and it will fill say with 3 cm of water.

A big bucket next to it will also collect 3 cm of water, but when you
empty the bucket you may have many cups full of water... literally buckets of signal compared to our small cup.

You could consider QE to be how much water the cup or bucket loses before you measure their contents.
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