I need some opinions on how much effect things like cleaning marks etc have on i mage quality. I use 4x5 and enlarge to 11x14 and shoot almost all B&W. The clean ing marks I'm talking about are on the rear element and can only be seen with a 7x loupe while pointing the lense directly at a quartz halogen lamp about 6in aw ay. I know that any kind of scratch or other imperfection will have an effect on con trast but does anyone know or have an opinion as to how much? I recall reading s omething written by Ansel himself stating that even a visible scratch on the rea r element would probably not have much of an effect unless struck by direct brig ht light! I am of the opinion that such minor imperfections have more of an effect on valu e than actual image quality as long as you're not enlarging a 4x5 to 5ftx7ft. An y other opinions? Also has anyone ever heard of or read anything about computar symmatrigons?