What are the directivity factor/index values for short shotgun and for long shotgun mics? I can't find this figure mentioned anywhere for shotgun mics. If a typical shotgun is equivalent in directivity to a 2nd-order super-cardioid, then it would be around 2.8 according to http://books.google.com/books?id=fcOAKtf9wdYC&pg=PA108&lpg=PA108&dq=directivity+index+microphone&source=web&ots=TaeQ2SyfTA&sig=UCzqLz5Oe6YjV_PH9IbMm28_CLk#PPA109,M1

check http://www.microphone-data.com/ for, um, microphone data ... includes polar patterns with gain/distance for various frequencies.

Mike, I've looked at that website already.

Using the term "distance factor" rather than "directivity factor" or "directivity index" produces more results.

This article is mainly interested in speech intelligibility and finds short & long shotguns to have a distance factor of about 3.

http://www.canford.co.uk/blueprintonline/blueprintaug2003/bigears.aspx

I presume the lack of a difference found between the short & long shotgun was due to the speech frequency range used and the interest in reducing the reverbant sound level rather than say unwanted low-freq traffic noise pickup. STI (Speech Transmission Index) was the used as the measurement.

Douglas Spotted Eagle, in this article, gives the distance factor of a line mic as 2.5.

http://presentation.digitalmedianet.com/2003/04_apr/tutorials/did_you_hear_that2.htm