This part of the enlarger is called a condenser.
And, what it does is, it sort of mixes light in here and lets it spread out evenly so you
can get a nice print. This is one part of the condenser. This is another part. This
is a heat plate, and what this does, it absorbs heat from the light source. And, it makes
it so that your negative does not get hot. If your negative got too hot, it could actually
buckle, and then give you a print that was out of focus and nobody wants that. And, your
condenser goes into different sections depending upon what format film you are using and what
size lens you are using. Now, at first, this confused the heck out me because I would have
prints that had edges missing and it took me a little while to understand what condenser
goes with what lens. But, up on this enlarger there is a little chart that shows you: eighty
millimeter lens, one fifty, normal lens, and where to put the condenser. And, that helps
me immensely to know how to properly set up this part of the enlarger to print.