Birding with a 500mm F4 or 600mm F4

Started Feb 1, 2014 | Discussions thread
JimPearce Veteran Member • Posts: 9,188
I'd be interested to learn more about this test Andy...

It seems to me that the laws of physics must have been suspended. The D800 at DX crop has 15.36 MP.  The D7100 has 24 MP. At ISO 1600 the SNR of the D7100 is 30.5 dB. Correcting the D800 for DX crop we get 30.6 dB. The DR of the D7100 is 10.72 Ev, the D800 corrected is 10.51 Ev. Call IQ a wash. Then let's look at the lens resolution. The D800 with the 500 scores 16P-Mpix. At DX crop that would be 7 P-Mpix. With the D7100 it scores 9 P-Mpix. Taking the square root, this suggests that the actual linear resolution advantage with the D7100 is about 13.3%. In other words, the D7100 has about the same reach as a 566mm lens on a D800. This is just over half of the 25% reach advantage we'd expect from simply taking sqrt(24/15.36). But it is not nothing.

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Nikon D7100 Nikon D500
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