I have a very well used 135 QC which doesn't have a large amount of contrast. If I have some time I'll clean it and see if removing some of the internal dust will make a difference.
Look for haze in the lens. That can easily cause a loss of contrast. It takes a fair amount of internal dust to cause a lost of contrast. If there is enough dust to cause a 1% loss of image quality would you notice?: If enough for a 10% loss, like that. I've cleaned only one lens out of maybe 50~55 over the years.
If the loss is from flare when pointed in the sun's direction that would be normal for a single coated lens. Even a broad area of hazy bright sky can cause a loss with a single coated lens. Always use a lens hood.
We're spoiled by Super Integrated Coatings and the occasional Nano coating. They do make a difference. Right now breakfast with coffee would make a difference.
Dave Hartman
