I am selling my FD system but I did decide to keep bellows and marco lenses. My plan is to use them with an adapter on the 5D.
I purchased an adapter (make: Kood) which has a lens in it. This lens which compensates the extra distance caused by the adapter, is not best quality optics I suppose.
My first approach was to remove the lens, which is not needed when using bellows. Optical this is the best solution but a better aproach came into my mind.
Drawback of removing the lens is sensor dust. Moving the bellows will blow dust on the sensor, there will be high amounts of dust in the bellows since I do not live in a clean room.
I proposed to mount a piece of non magifying glass in the adapter. I already packed the original lens to see an optician when it came into my mind that glass for glasses probably has some coating.
What is the best place to get clean optical glass?