I have some ignorance that needs fighting. re: film speed.

Factual Questions
1

Hiya all…

I am a photographer, and I use 400ISO/ASA speed film mostly for my work.

I was thinking about people who make motion pictures and wondered if there was a similar method of rating motion picture film for use in different lighing conditions, like I would use 100 or slower on a bright sunny day and 400 or faster for indoors and cloudy/nighttime work.

Is that the case? Someone once told me that motion picture film is 25 frames per second, but I’m not sure if thats what I was wanting answered…
Thanks in advance!!

Lee

2

I thought this was film: speed in the sense of “there’s a bomb on the bus”

Sorry, I can’t help with your question.

3

:slight_smile:

yeah. is a little misleading… I apologise…

4

Ummm…if I think I understand what you’re asking then, yes, motion picture films do have different ISO ratings. I am a professional still photographer, but I do NOT have motion picture experience. From what I do know, motion pictures are generally shot on film in the 200-320 ISO range. There’s a Kodak 250 daylight-balanced film and a 320 tungsten-balanced film which seems to be among the more popular. AFAIK, 800 ISO is the highest speed generally available for color motion pictures.

Is this what you were asking?

5

Film speed and frame rate are two different things. Actually the standard rate for 35mm and up cine is 24 frames per second IRRC with 16 and 8mm at different, slower standard rates.

Film speed is just another way of saying sensitivity to light and the same rules apply to cine as they do to still cameras. Because the frame rate is fixed unless doing special effects there is no way to vary the shutter speed in most cine cameras so exposure has to be controlled by aperture and choosing the correct film speed for the lighting conditions. There may be some sophisticated cine cameras out there that can expose the frame shorter than the frame interval but no way to expose it longer or the frame rate would be changed.

6

25 FPS is how fast the film passes through the projector in the movie theatre. It has nothing to do with film sensitivity.

I’m not a cinematographer, but I can think of no reason why motion picture stock couldn’t be produced in different light sensitivities, just like still photography film. It’s basically the same stuff.

The trouble with changing film stock when shooting different movie scenes is that the films, along with having different light sensitivity, would almost certainly have different color balance and grain. When the film was edited together and projected, you’d probably be able to tell when the film stock changed from one type to another, unless these differences were compensated for during filming or in post-processing.

7

I hadn’t thought of that. That’s very interesting. Could neutral density filters also be used?
Incidentally (re. my previous post), I know that film makers have to deal with color shifts on their film even if they always use the same stock. In fact, different cans of the same stock might have subtle differences. An outdoor scene can be shot over a period of several days, at various times of the day and in changing weather. This can change the light quality of each film clip dramatically, which would not do if the scene is supposed to occur over only a few minutes. These changes have to be compensated for, either during filming or in post-processing.

8

They also have much more control over lighting conditions, at least for ‘proper’ movies with a decent budget. Even in broad daylight on location you can often see great banks of artificial lights and guys running around with light meters.

9

It’s 24 fps and nothing else; 25 fps is video. Hell of a problem when you shoot on one medium and want to transfer.

pulykamell has basically got it down regarding speeds of stock. There are some odd stocks that go higher and lower in the ASA and DIN ranges but as I said they are odd and rarely used.

padeye and ticker are right, but I don’t know about all those guys with light meters. It’s usually only the DP (director of photography) and his/her closest cohorts measuring lux (light). There are far more guys, so called gaffers, best boys and electricians carrying around lights and pulling cable. Your average film uses several km of cable, lots and lots of daylight , neon-type and tungsten ‘lamps’ and megawatts of electricity. It’s usually a very expensive part of the shooting budget.

Sparc

10

I’m up way too early on a Saturday morning, and I haven’t had coffee yet. Still…

Frame speed: For theatrical releases, film runs at 24 frames per second (fps). Video in the U.S. is 30 fps, and in Europe it’s 25 fps. European films shot on film for release on video are shot at 25 fps to match the video frame speed. 35 and 16mm film run at the industry standard. Super-8 runs at 18 or 24 fps. Regular 8mm ran at 16 or 18 fps.

Film speed: When shooting 16mm, I normally use colour Fuji 125 tungsten balanced film or Kodak Tri-X or Plus-X at asa 160/200 and 40/50, respectively. The speeds are the same as for still stock.

Exposure: The aperture is controlled in the same way as with a still camera. Zoom lenses use T-stops instead of f-stops to take the extra optics into account. Many cameras have fixed shutters of a given angle, while others have variable shutters. Light can be controlled by opening or closing the shutter. This can also make for some interesting effects. For example, in Three Kings they used a rather narrow shutter angle to give some of the shots a strobe-like quality.

As has been mentioned, lighting is more controlled on a film set than in many still studios. Or perhaps I should say that it’s controlled differently to create a different effect. In addition to adding or subtracting lights and reflectors, filters can also be used. Sometimes they have to be used. For example, if I want to use tungsten-balanced film outside, I need to use a #85 orange filter. This reduces the amount of light reaching the film by 2/3 stop. On an especially bright day/set, you can use neutral density filters to reduce the light hitting the film.

Unlike a still camera, a movie camera’s shutter speed is fixed (except for special circumstances). While still photographers are used to setting the aperture for depth of field and adjusting the shutter speed for exposure, or setting the shutter speed for, say, a fast-moving subject and adjusting the aperture for light, a cinematographer has to use the aperture only and control light external to the camera. That is, he can open or close the aperture, add or subtract light, add or remove a filter, and that’s about it. Changing the frame speed changes the speed of the action – which you may or may not want to do.

Meters: I use a Minolta Auto IV that displays the F-/T-stop directly. Very handy little gadget, and much easier to use than my old Sekonic.

11

Thanks for your help everyone… I appreciate it.

I now understand what I was talking about :slight_smile:
this thread can decend into obscurity now :smiley: