Using a Bellows
The most logical way to get an enlarger lens to focus when using it on a camera is to replicate the bellows of an enlarger using a set of macro bellows. Mount one end of these bellows to the camera, and the other to an M39 mount to allow enlarger lenses to be used. Some bellows, such as the old, but very popular BPM Universal bellows, or the Novoflex Universal BALPRO 1 (www.novoflex.com/en/products/macro-accessories/bellows-systems/universal-bellows) allow various combinations of lenses. For example, an M39 mount can be connected to the front of the bellows and a Nikon F mount to the rear, to allow enlarger lenses to be used on a Nikon camera.
At the very short extensions of the bellows, an enlarger lens may just about be able to focus on infinity using a compact system camera, but the larger flange depth means that infinity won’t be available on a DSLR. Instead, the enlarger lens will only be able to focus at very close distances on a DSLR. Also, by extending the bellows on a DSLR or a compact system camera, the enlarger lens will make an excellent macro optic.
The simplest, but least exact, method of using an enlarger lens is to shoot handheld. With no lens mounted on the camera, wrap the enlarger lens in your hand and press it up against the camera mount. Moving your hand back and forth, it should be possible to roughly focus the lens.
It is extremely hard to hold the lens in the correct position to focus, and consequently images will tend to be soft. Similarly, it is difficult to match the horizontal plane of the film and sensor, so there will usually also be a slight tilt-and-shift effect, often with quite a narrow focal plane.
Despite the obvious flaws in shooting handheld, this method can produce some striking images – unique, too, given that it is so difficult to take exactly the same image twice.