Guys,
This is Nasim, the guy who wrote about the Df shutter issue. After I researched the issue more and received feedback from our readers, I realized that I posted about the problem without fully understanding the cause of the issue. It turns out that artificial light can result in huge variations in exposure at fast shutter speeds above 1/125. I have seen flicker issues before, but this particular case was odd, because the image was very dark. Either way, I stand corrected and I wanted to apologize in front of everyone that read the original article.
Please remember that I am a human and I make mistakes. This was a good lesson learned, so I re-wrote the article with a different title and content for those that might encounter a similar/same issue in artificial light.
Thank you for understanding.
Sincerely,
Nasim
http://photographylife.com