Andrew, great video. I had decided my conclusions before the end of the video and when you stated yours, mine were exactly the same.
Quite some time ago I watched a video by someone who had no known pedigree, nor was he known by anyone on Photrio and what he did was to shoot D400 at 3200 and compare the former with the Iatter then posted his video on Photrio. He used Microphen. His D400 pushed to 3200 looked pretty good as well. So in the hope of producing a balanced discussion on it, I posted his video in March of last year
I have just re-read it and whereas your video has not has any negative responses I cannot say the same for the one I posted, especially at the start of the thread. However as I said the video maker was not known and thus by definition not respected here unlike yourself
Still I tried to ask questions and eventually the discussion became more balanced but initially the reaction to the video was like the very negative one that Calvera in "The Magnificent Seven" got when he described being chased by the whole American army for robbing a bank in Texas. He realised that in Texas only Texans can rob banks

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Anyway your video proves that D400 can be pushed to at least 800 with almost no ill effect and in those light conditions and for most of your subjects 3200 gave only a slightly poorer result
Thanks
pentaxuser