Green Ghosts

I have noticed one isolated image artifact which I am unable to explain. The frames below in Fig. 4 were taken in an underground parking garage lit by sodium vapor lamps. In the Leica M8 frame there are very clear green ghosts on the left side of frame, of the bright light fixtures on the other side of the frame. These can be seen more clearly in Fig. 5 which is a 100% crop. No image processing from the raw file other than a white balance on the cement floor has been done. The Canon 5D shot is shown as a point of reference. My original intention had been to use these shots to compare high ISO performance, but the green ghosts became more significant as I examined the files on-screen.

Figure 4

Figure 5

As I wrote above, I am at a loss to explain these. They do not appear to be optical artifacts, yet it is hard to imagine how they can be sensor artifacts. I have tried to duplicate this using a variety of other light sources, flourescents, tungsten bulbs, halogen bulbs and LEDs, but without succcess. It appears to only be seen with sodium vapor (very green) bulbs. ISO does not appear to be a factor.

But, when I happened to be in another parking structure with sodium vapour bulbs (though ones with a seemingly different colour) try as I might I couldn’t repeat the effect. My only conclusion is that it may have something to do with the extended green sensitivity of the M8’s Kodak sensor. This is seen and discussed above, and shown in Fig 3. When M8s go into general distribution I will be curious to hear whether others are seeing this anomalous behaviour.

Since maybe .0001% of the shooting I have ever done in my life is under such lights it isn’t something that particularly concerns me, but I will be curious to find out the cause, and solution.}