The film negative is the same size, right? What are the specs of the lenses they use?
The film is the same size, but it travels horizontally in SLRs and vertically in Movie Cameras. This means that the negative per frame is about twice the size in an SLR. That being said, a lot of telephoto lenses by Nikkor and Canon are converted to Movie Cameras. In terms of specs, the main physical differences are that MC lenses have a larger focus scale with a lot more specific distances printed on them, and they use T-stops instead of F-stops. T-stops are measured lens by lens, while F-stops are based on a mathematical formula. The expanded focus scale enables the focus puller to accurately follow the action, “racking” easily between 6 and 7 feet rather than trying to move a smaller scale a fraction of an inch between the two distances. I hope that makes sense. As far as resolving power goes, while they are probably better than typical consumer level SLR lenses, the higher end SLR lenses are equal to or even superior to MC lenses. (No cite for this, but I have heard (ghastly SDMB rumor monger that I am I will repeat it) that the best lens for resolution ever tested at Panavision in Woodland Hills was a 200mm Canon.) MC lenses are also coated with, well… coating, to reduce flares from light hitting the elements. In terms of price, while MC lenses are VERY expensive, the most sought after SLR lenses are even more expensive. Hope this answers some of your question. If actual size is what you’re after, a 50mm Panavision Primo prime lens is about 10 inches long, weighs about 5 pounds (rough guess) and is essentially like a tapered version of an old-school Hawaiian Punch can (large size) with a lens mount at one end.
Wow, sounds like none of the numbers are directly comparable. I was actually wondering mainly about the f-stops, since I figured they could easily afford stuff that is very pricey in SLRs, like 50mm f/1.0 lenses.
Do they generally use primes?
Wait, I just reread what you wrote. A 50mm lens is 10 inches long? Can anyone explain that one?
Coven didn’t make it explicit. The film gauge is the same (35mm), but the frame size is not. The full aperture 35mm movie frame is four perfs tall, with an area about 17.5 x 21mm. A 35mm still frame is 8 perfs wide, about 24 x 32mm, more than twice the area of a movie frame. So all other things being equal (which they usually are not), a still lens would be significantly over-engineered if used on a movie camera. Which would result in better images on the film frame.
FYI, IMAX movie cameras, which expose a 70mm frame of 52 x 70mm, use the Zeiss lenses made for Hasselblad cameras.
50mm designates the focal length, not the overall size of the lens. That nominally measures distance from the rear node to the film plane and is a handy way to calculate angle of view for a given film plane size. The physical back focus distance can be changed, longer or shorter, while maintaining the same angle of view. A retrofocus design is used to a very short, wide angle lens isn’t physically inside the mirror box and interfering with the moving mirror of an SLR. The rest of the lens will no doubt include many glass elements to correct optical defects such as chromatic aberration. There are advantages to having the lens be much larger than the focal length would indicate, particularly in a cine cameral. 45-50mm still camera lenses (for 35mm cameras) usually have the smallest physical size because there is no reason to make them artificially larger.
In terms of F-stops (T-stops in cine), speed is no longer all that sought after. T 1.0 lenses are available, but most Directors of Photography choose to shoot with either Panavision Primos, Cooke S-4s, or Zeiss Ultraprimes. The Primos are all T1.9, The Cookes all T2.0, and the Zeiss are mostly T1.7. The choice of which to use is based on contrast, colour, and other DOP type considerations I know nothing about.
Primes are usually the first choice of most DOPs for shooting. However, when time is of the essence, many will use zooms quite happily. The Panavision Primo 4-1 (17.5-75, T2.3) and 11-1 (24-275, T2.8) are used all the time as they are considered to be the virtual equals of the primes. Zeiss makes a series of three “variable primes” which some swear by. With the Cookes most choose to take the Angenieux 24-290 “12-1”, a 25 pound T2.8 behemoth.
As far as the 10 inch long 50mm Primo prime lens, I was being a bit disingenuous, as it was the largest prime lens I could think of. Most primes are considerably bigger than any SLR prime lens, but are as a rough average about 6 inches long and about 4.5 inches in diameter. I think the expanded focus scale really does affect the size quite significantly. In order to make focus pulling easier manufacturers try to make the focus marks well spread and consistent lens to lens, which I assume makes the circumference of the lens larger. Definitely could be talking out my ass on that one though, as I am very far from being an optical engineer.
Oh, and as long as we’re talking about lenses, the craziest thing I’ve ever seen is the Nikkor 6mm. It is a still lens also used as a cine lens, and the front element looks like a hub cap from an old chevy made of glass. When you’re standing behind the camera, if you put your hands in the air, you can see 'em! (It’s the one on the left.)
I think I read about lenses for movie or perhaps video use that had an image size similar to SLR but had features like 10:1 or 20:1 zoom ratio along with speeds like f/1.4. The price was perhaps $50,000.
Of course, it’d cost a great deal to make a lens with those abilities. I remember wondering at the time if the moving picture format let them get away with poorer resolution than SLRs do, which would make such a lens more believable.
Anybody know what I might have read about? It doesn’t sound consistent with the above. Maybe these were lenses used for video cameras at the Super Bowl or something?