Quote:
Originally Posted by gregbradley
There are already sites that post measured QEs of various digital cameras. With all due respect none are as low as 10%. 10% would mean they would not be able to take a photo in any sort of dim light and we know that is not true. This is getting a bit subjective and opinion rather than fact.
Greg.
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different measures of QE Greg - we are comparing apples and oranges.
With DSLRs, the widely used QE measures gloss over the fact that about 2/3 of white light photons never actually get to the sensor (they are absorbed in the Bayer filter). That is fine for comparing DSLRs, where you can assume that all Bayer filters are similar and the performance of the underlying array is what distinguishes between cameras. However the use of the term "QE" without any qualifications causes confusion when comparing DSLRs with mono chips.
A mono chip has no Bayer filter so it sees about 3x more white light photons than an OSC (regardless of how many photons either underlying array detects). Thus, broadband QE for a mono chip starts out about 3x better than that of an equivalent DSLR - something that is completely hidden by the methods used to measure DSLR QE.
Results from the two different ways of measuring QE are well illustrated in
http://www.astrosurf.com/buil/50d/test.htm (figures from that below) The first figure shows QE measured the DSLR way (pixel QE in the left hand panel) and the broadband way (geometric QE in the right hand panel). The second figure shows the QE of some DSLRs when compared with a 3200 and when accounting for broadband illumination - the broadband QE is the sum of the 3 colour curves and this figure clearly shows the "chasm" between DSLR and mono when QE apples are compared with QE apples. .
This thread is about broadband QE and Buil's results match Richard's observation that a good DSLR may have an average broadband QE of around 10-15%. Of course 10% is still very sensitive - it is about an order of magnitude better than a fully dark adapted human visual system. In any event, it is not physically possible for the broadband QE of a Bayer DSLR to get much above 30% using any detector technology, so 10% is not bad.