Yep, many have seen it, and I'll echo much of the same already said. That's actually not too bad, compared to some of mine at times.
I have a
lot to learn to ensure properly exposed photographs.
joekr, wondering by how much you increased the brightness / exposure by over the original image? I do know that I've never seen that unless I push the exposure of the underexposed image in post. Would you be willing to use a capture program or some other method and post the
original histogram of the image before modified by an image processing program? The general concensus of many is if shooting ISO 1600, to bias the histogram to the right of center w/o over exposure,
when & if possible. No, it's not always possible; otherwise then, a dark image is a dark image.
But if that is done, ISO1600 images are excellent.