Well of course they are not as with every new camera and firmware update less and less 3rd party stuff works with Nikon. Just sold a 18-200 and 18-250 Sigma because did not work with D7100 ...Lcd timers would not function. fine on the old D7000 . Similar problems with grips and on D800. :
@)
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Sigma has responded to this with an additional USB add on where you can update Sigma lenses for new Nikon cameras. The 35mm 1.4 Art Lens has this. Time will tell if this works.
Of course, Schneider and Zeiss avoid this problem completely by not producing auto-focus F-mount lenses.
It is a bit of a blessing in disguise though to be honest that lens has nowhere near the optics to compliment the D7100's awesome sensor.
And I am suggesting that the firmware to reject thrid party stuff will become more aggressive which it has over the last 12 months
One just needs to understand just how many lenses are sold at different levels to understand why they are not afraid. They make more on the cheap consumer lenses and sell gobs more of those. Loosing out on some low margin sales of the "pro-style" lenses isn't really a big loss.
Consider this:
35mm 1.4g lens has sold somewhere in the ball park of 29,500 lenses worldwide.
18-105VR - 4,634,822 Lenses sold.
If Nikon looses out on a couple thousand sales to Sigma for a 35mm 1.4 - what's the big deal? Nothing.
One of my favorite sites to find these numbers.
http://www.photosynthesis.co.nz/nikon/serialno.html
you know an Dx F mount camera 24 mp, 8-10 fps, big buffer pro build and controls, high ISO
TTJ: Good point. The numbers just aren't there for Nikon to worry about.
sevencrossing: Surely could be done and would give any third party immediate off-the-shelf access to a complete range of lenses so they wouldn't even need to produce any of their own. However, Nikon must have a patent on the F mount and would sue any third party which tried to market a body with the F mount unless Nikon licensed that mount to them which it won't do. Nikon's extensive line of "legacy lenses" is a great asset the company is not going to share with any third party by giving them such easy access.
the AF came out in 1986 and would have expired in 2006
there will be patents on later improvements but how do third party lenses get round these ?
When Sigma's actual AF came too close to the OEM's AF, they were indeed sued by Nikon. (I think it was settled before trial.)
Who said that? A Nikon person? Simple answer: Because it would make them look stupid if they said something different, i.e. "Yeah, we're following the development on the 3rd party lens market and I must say: We're pretty scared of losing sales. The quality has become awesome. We really need a strategy here."
Why would anyone philosophize about "reasons" for them not to be worried, just because some corporate person said they weren't? Of course they are. It would be stupid not to.
Concerning the numbers @TaoTeJared is quoting (great source, thanks!): Yeah, the volume is small if you look at the 35mm goldring prime. Then again, keep in mind that the margin on a ~1500-dollar prime lens is rather big compared to a consumer-level zoom. But it changes quite a lot if you look at things like the 50mm 1.4 or the 24-70/2.8.
You can bet they are worried. And they are right, too.