I have an Omega Universal 4x5 enlarger with the variable condenser. I do not have the variable, "movable" condenser and wonder what it does? If I understand it is not really needed when enlarging 4x5 negatives but is when enlarging smaller format negatives.
Usually they alternate condensor lenses, or alternate condensor lens placement focus an even distribution of light intensity across a smaller area, so you can achieve faster printing times, if you want to, for negatives smaller that the maximum size the enlarger can handle.
To add a little to Mike's comment, the box above the fixed condensers has three positions to place the variable condenser to give you a concentrated (or not) light beam for smaller negatives.
On my Omega D2, the third lens in the variable condenser is not needed for lenses around 150mm and longer, but has three positions for lenses 135mm and shorter.
I found a variable condenser and I am using a 135mm enlarging lens. I found that it keeps the time from being so short. I was also having a bit of a problem with the exposure being too shot to burn a dodge.
If I read Strad correctly, he does not have the movable (i.e., variable) condenser. In that case, he would need individual condensers for the different lenses. I now have a D2V, the variable (movable) kind, but I started with just a D2. I had to change condensers when changing lenses (50, 80, 105, 135/150). Not a major pain, but it was inconvenient. Assuming you have the condensers in the first place.
I found a variable condenser and I am using a 135mm enlarging lens. I found that it keeps the time from being so short. I was also having a bit of a problem with the exposure being too shot to burn a dodge.
Do you mean you have the condenser that is moved depending on the lens or your a non variable condenser that swaps out? In any case what blub are your using, 75, 150 or 250 watt?
I have a D5XL with the variable lamphouse but did not have the moveable condenser. On Friday I found the movable condenser. So we will see if that makes a time difference.