For Lawrence of Arabia, director David Lean used a 482mm (19in) lens to show a rider coming out of a mirage. What is such a huge lens used to do? What effect does it have on the shot?
The longer the lens, the more telephoto it is. I’m not familiar with 65 mm gear, but for 16 mm cameras a 25 mm lens is ‘normal’ – it basically gives a field of view similar to what you see with your bare eyes. A 50 mm lens is ‘normal’ on a 35 mm camera. So I assume that a ‘normal’ lens for a 65 mm camera would be about 100 mm. If that’s the case, the 482 mm lens would be about 5x magnification.
I’m not familiar with film gear but FWIW the measurement is referring to the (optical) focal length of the lens - it doesn’t necessarily measure 19" in any physical dimension.
Quick nontechnical answer - compared to a shorter lens, a long focal length gives you a narrower angle of view, a shallower depth of field for a given aperture, and due to the magnification can provide an apparently “flattened” perspective.
Foreground-background compression. The more telephoto a lens is, the more it will appear to compress the distance between the foreground and background.
Strictly speaking it’s the distance from the camera to the object that changes the perspective, not the magnification of the lens. A telephoto lens lets you see a different perspective by moving further away.
I understand, and was (apparently unsuccessfully) trying to say the same thing (that is, it can provide a “flattened” perspective compared to a shorter lens, as a result of the necessarily longer working distance for a given framed subject).
This video of a dolly zoom shows you how the relationship of foreground-to-background works. The video starts with a wide angle and slowly zooms into a telephoto shot, while the camera is being pulled back to maintain the same general field of view. Note how the telephoto lens seems to bring the background closer and closer to the subjects.
Now, I’m not familiar with the scene in question, but I assume something about the background and trying to collapse it in with the subject for dramatic effect would be one reason to choose a very long lens. The other reason (and this is related to the foreground-background compression) would be to capture the “heat waves” off the sand. Shooting with a short lens, you don’t really see the heat distorting the image. You need to shoot through a bit of atmosphere to get dramatic heat distortion in your images, and the longer the lens, the more heated air you’re shooting through and the more pronounced the effect.
David Lean wanted to have Sharif enter through a mirage. I can’t think of a good way to describe this, but I assume that the telephoto lens was used to increase depth of field to have more “stuff” moving around to emphasize the effect. If the lens only focused on Sharif, then there wouldn’t have been anything to use as a reference and it may have come out as a distorted image and nothing more, not as a mirage.
Slightly on-topic: I believe parts of The Endless Summer (1966) was shot with a 300 mm lens. The camera was a spring-motor Bolex H16, 16 mm camera; so that would have been a 12x zoom.
If he wanted more depth of field, a wider lens is usually the choice. Telephoto lenses tend to be used for their isolating ability and lower apparent depth of field. Watch the video of the vertigo effect above. Note how it starts wide, with lots of depth of field, and then ends telephoto, with very shallow depth of field (look at the background.)
All else being equal, a telephoto lens has a narrower depth of field.
Technically, that’s not quite true, which is why I use the word “apparent” in my previous post. A little more on DOF. However, for all practical purposes, that is how photographers generally think about their lenses, that the more telephoto ones have shallow depth of field and the wides have great depth of field, even though that’s not strictly true.
Facepalm. You’re right - I should have known that.
Eh, no big deal. I’d wager the clear, if not vast, majority of professional photographers don’t know that. We think of telephoto as isolating, shallow depth-of-field, and wides as sharp all over, easy to get hyperfocal. For practical purposes, it may as well be true, even though technically it’s not.
Good stuff so far.
From post # 2
A custom made 450 mm lens. Created by Panavision ( originally of Tarzana CA, now of Woodland Hills CA though that may change again… ).
The whole depth of field thing. In what I would consider to be the normal range of available light situations, things swim in and out of focus like a bad dream at 200mm no less 450. But think about it. It’s the real desert. The amount of light bouncing off of the sand back up onto the actors ( and therefore the overall ambience ) is simply astounding. Try taking a light meter to the beach. Or on a bright sunny day the morning after a serious blizzard where all is white and snowy.
I don’t have my American Cinematographer’s Manual handy, but at 450mm with, say, an f22 or better the depth of focus would have been quite respectable. More than good enough for an ace focus puller to keep the actors in critical focus. Add to that the aforementioned beautiful mirage swimming of the superheated air above the sand.
There’s out of focus, but then there’s a sharp image within which are elements that are being moved around. Decades before CGI, Freddy Young created a moving painting. Elegant, tone-setting- soothing, interesting.
The lens is infamous in film camera circles because it was made for this one shot. Sort of like the NASA lens that Stanley Kubrick heard about that shot at T .9. He had Ed DiGuilio at Cinema Products modify the mount so it could be used on an Arriflex to shoot Barry Lyndon in a shot lit with a single candle.
We’re geeks. 
Cartooniverse
IATSE Local 600
Long focal lengths in portrait photography actually make your subject look smaller. There’s a straight dope article on this. I made an example MacBook aNd I: Zoom and perspective
What you have there is related to the compressive effect mentioned above. Your mouseover example exaggerates the effect a bit (I think you could have done a better job in keeping the relative sizes of the bottle the same in the two pictures), but basically what happens is with the longer lens, the distance from the front of the subject to the back of the subject looks foreshortened. I wouldn’t really characterize it as making your subject look smaller.
Here’s a much better example on faces. Note how the shape of the face changes and becomes more “mousy” as you decrease focal length (and, more importantly, decrease your distance-to-subject, as this is really what causes the change in perspective). Note how the distance from the tip of the nose to where the ears would be, or the distance from the chin to the top of her neck seems to get farther and farther the more wide you get. This is why generally lenses in the 85mm-200mm+ range are considered good portrait lenses. Foreshortening is generally pretty flattering on faces. I disagree that they make people look smaller and slimmer. They’re just more flattering and, I would say, fuller. Wider lenses don’t make people look fat, in my opinion. Look at the wide examples above. They just make people look weird and distorted, and a bit skeletal, to be honest.
An excellent example of the depth-of-field compression effect:
In the film The Graduate:
Near the end of the film, Dustin Hoffman is trying to get to the church and his car runs out of gas. They cut to a scene showing him running towards the camera.
They used a long lens to film this scene, so it gives the impression that he is perpetually running towards the camera, but getting nowhere. Quite an effective use of DOF.