David, if Robert was to use a 135mm enlarging lens on his enlarger with a 6X9 negative. Let's say he was making an 8X10 enlargement. Then, he raised the enlarger head up to make an 11X14 enlargement from the same negative, with the same 135mm lens. Are you saying that the exposure time would not increase? It sure increases on my enlarger set-up. Now, if he were to change to a shorter lens, he wouldn't need to raise the enlarger head to make the 11X14. His exposure time would not increase. The distance between the enlarger lamp and the paper would remain the same. The higher I raise my enlarger head to make bigger prints, the longer my exposure times become (F stops remaining the same). I stand by my statement. Use the shortest lens that will adequately cover the format (in this case 105mm). It makes the enlarging experience much easier. And Robert, I have seen darkroom set-ups where a section of the ceiling above the enlarger was raised to accomodate a long enlarger column.