D600/D800 Firmware Update Coming

We can't be sure because we haven't had access to the rumored firmware update. But reverting to a previous firmware version has certainly not been possible in the past with Nikon dSLRs. That's why some deliberately wait for others to try it out for a few weeks before installing the update on their cameras.

So far Nikon's firmware updates have always been reliable to my recollection.

Also don't keep your hopes too high. It would not be the first time rumors surface about a firmware update which never materialize beyond the state of vapor ware.

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Thierry