This is an older 50mm 2.8. Where I'm pointing at with the pencil is where the light is coming from. As I adjust the aperture, the darker circle widens. This is not normal with this lens correct? This will be the second defective lens purchase from ebay in a row, which is a shame because the glass is in near perfect condition. Also, the glass plate that protects the negative from heat..for b&w printing, is the light blue color an issue or should it be clear? Thank you *Edit - Sorry..this should have went in the equipment section.