I have a Omega D5 Pro-Lab enlarger with condenser head that I purchased used recently which has an odd problem: when I have a negative carrier installed and focused (and the enlarger on) there is a sharp rectangle of light projected through the negative carrier onto the easel as you'd expect, but there is also a faint, but obvious circular pool of light that is the same diameter as would be projected if the negative carrier was not installed. It is almost as if the negative carrier was slight translucent... I've tested multiple negative carriers both black metal and black matboard and they all exhibit the same problem. The pool of light is definitely strong enough to fog a print unless the easel arms completely block the non-printed portion of the paper. I've tried multiple lenses and they all show the problem, though with some it is more pronounced than others. The problem is more or less pronounced depending on the lens aperture, but it is there for all apertures. I've also tried both a standard flat lens board and a three lens turret, the problem shows up with all. And I've tried multiple bulbs, both 75W and 150W - all exhibit the same problem. I've verified that the condenser is installed problem and the alignment appears to be good; though it might need some slight adjustments, I can't account for this behavior on the basis of alignment. (Though of course that doesn't mean I'm right.) (I've checked another D5 enlarger at a local photo lab and they have no such issue). I've included two images with this post. These are simulations of the problem. The first simulates the pool of light without the negative carrier - this is clearly just a white pool of light on a black background. The second simulates when a negative carrier is installed. Here you see the sharp bright rectangle you'd expect, but also a faint pool of light the same diameter as the previous pool of light. It is that faint pool of light that I'm concerned about. Has anyone ever seen something like this before? Does anyone have any ideas what could possibly be causing this problem? I've asked several photography friends, some with decades of experience, but no one has an answer. Any help or suggestions would be greatly appreciated. Many thanks, John.