I bought a second hand Tri Elmar 28-35-50 (first version) recently. At the 28 and 35 mm settings the results are superb but at 50 mm, there is a noticeable reduction in contrast in the upper middle of the image which shows up in the final image as though it was lens flare and spoils the image. This is present whether or not I use a hood and is a feature of the lens using both film and digital media. I have rung Leica about this but they didn't recognise any such problems with this lens. I have also looked through all the relevant written material including Erwin Putts book on Leica lenses, and found no mention of this effect although it is so noticeable that it would be immediately obvious to anyone using it. Has anyone else experienced this - or do I have a duff lens?