The term ‘telephoto lens’ is nowadays generally misapplied to longer focal length lenses, as opposed to wide angle lenses. In fact, ‘telephoto’ has nothing to do with focal length, but designates a particular lens design. But photographers generally don’t concern themselves with the intricacies of lens construction, yet in this case it makes a big practical difference when using a view camera.

A photographic lens gathers light from the subject into a cone that focuses it into a single point, from which it is then projected out as another cone in the opposite direction onto the film. The constriction between the two cones is called the nodal point, and its position determines focus: a lens is focused at infinity when the nodal point is at a distance from the film that matches the focal length of the lens; to focus it closer then that, the nodal point needs to be moved further away from the film.

Large format camera lenses are made up of two opposing cells screwed into a shutter, which in turn is attached to a lens board; the board then gets attached to the camera front plate. The front plate provides the front camera movements, with the axis of ration (vertical and horizontal) being on the lens board plane, usually (and preferably) in the centre of it.

For a normal lens this is all arranged so that the nodal point of the lens lies on the plane of the lens board, which means the two axis of rotation are passing through the nodal point. The beauty of this arrangement is that the distance of the nodal point from the film doesn’t change when you apply any of the movements, i.e., if you focus a subject in the centre of the image, it will remain in focus. This makes adjusting the movements simpler.

The main limitation of this design is the bellows extension required to focus the lens: for a lens with a 300mm focal length (which for 4x5 camera is about 100mm full frame equivalent), you need 300mm extension to focus to infinity, and considerably longer for doing close ups.

This is problematic for a number of reasons: the focusing rail needs to be long enough to allow this, long bellows might not compress enough to get you close enough to the film when using, e.g., a 75mm wide angle lens, and they also suffer from sag. This is all possible to accommodate in a big studio camera, which can have a long rail and big, and/or multiple swappable, bellows; less so in a field folder design, the practical limit for a 4x5 folder will often be below the 300mm mark, perhaps 240mm or so.

But we want to be able use longer focal lengths than that, and the telephoto lens design comes to the rescue: a telephoto lens is, through pure magic and trickery, constructed in such a way that the nodal point lies in front of the lens. So if you have, for example, a 400mm lens where the nodal point lies 200mm in front of the lens board, you only need a 200mm bellows extension for focus at infinity.

The price for that is that the movements applied to the camera change the distance of the nodal point from the film, and so alter focus, plus tilt and swing gain an implicit rise and shift, e.g., when you tilt the image, it also moves up and down. This makes it much more awkward to work the movements, as you have to refocus and redo rise and shift after each adjustment — getting what you need from the tilt and swing becomes much more involved.

In addition to that, telephoto lenses tend to have a much smaller image circle, so what you can do with them, in terms of movements, is more limited. Plus the front cell is long, exerting considerable torque on the lens board, and so they tend to tip forward when you loosen off the front tilt controls, which makes minute changes very tricky.

The bottom line is, if you are after a longer focal length lens (300+mm) for a 4x5, you might need a telephoto one, rather than a normal one. The normal lenses in these focal lengths, of course, exist (not least because 300mm is ~50mm full frame equivalent for an 8x10 camera), but your 4x5 might not be able to handle them at all, or adequately. But I find even 400mm telephoto is on the limit of usability with even a decent 4x5 folder like the Chamonix.

And if you do get a telephoto lens, be prepared for the extra fun in working with it. But it’s all worth it when things come together the way you want them to. 🙂

PS: There are various lists of LF lenses and their specifications online, largeformatphotography.info is the best starting point for all things LF.