Quote Originally Posted by dancqu View Post
An enlarging lens extended for 1:1 ratio enlargements
has 1/4 the speed; is two full stops slower.
The two systems are equivalent for practical purposes. Either the effective f-stop is two stops slower (the f-number is twice as big) because the lens-film distance has doubled -or- the amount of light is 1/4 because the area covered is 4x area / 2x linear larger.

Don't use them together ...