>>But when he uses 1/2 shutter to >>focus there is a red flash visible on the edges of the >>viewfinder image. > >I've noticed the red flash occasionally on my D600. I'm >virtually certain that what we're seeing is simply the red of >the auto-focus assist light which comes on to aid auto-focus >in low light conditions. I believe the auto-focus assist can >be turned off, so if the red flash disappears when it is >(which I haven't done yet, although I'll try it the next time >I'm focusing in low light), there's the culprit for sure. >Naturally, I'd be interested in anyone else's thoughts here.
Yes, I have seen that as well, in very dark conditions. However, my brother sent his D600 in, and they agreed it was electrically challenged, and cheerfully replaced it. The replacement functions well, and has no dust or oil spots as yet. Neither does mine at 999 images, and both of us are most impressed with its quality.