Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
 
|
Post by Flynn on Sept 15, 2017 3:12:32 GMT
I wasn't sure where to post this question, so I thought I'd put it here, since classic film enthusiasts might have a better understanding of the techniques of film photography.
Does anyone here know how exposure works in moving picture photography? What I'm wondering about is how one handles shutter speeds in moving-picture cinematography. If I take a still picture in low light, for example, I might have to adjust a shutter speed to be 1/30 or 1/15 of a second. So, in a medium where one needs a constant 24 frames per second, how is exposure compensated for? It can't be with shutter speed or aperture, so how does exposure work?
|
|
|
|
Post by vegalyra on Sept 15, 2017 13:26:32 GMT
Interesting question. I'd like to know an answer to that as well. I actually never thought about it before...
|
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 15, 2017 13:56:20 GMT
I wasn't sure where to post this question, so I thought I'd put it here, since classic film enthusiasts might have a better understanding of the techniques of film photography. Does anyone here know how exposure works in moving picture photography? What I'm wondering about is how one handles shutter speeds in moving-picture cinematography. If I take a still picture in low light, for example, I might have to adjust a shutter speed to be 1/30 or 1/15 of a second. So, in a medium where one needs a constant 24 frames per second, how is exposure compensated for? It can't be with shutter speed or aperture, so how does exposure work? You have to adjust the f-stop to a wider aperture to let in more light, and possibly use a wider angle lens, both of which, of course, affect depth of field. It also depends upon the ASA or speed of the film stock you're using. The higher the speed, the less light you would need, so the depth of field could be manipulated by using longer lenses and lower f-stops. Higher ASA stocks began to be used regularly in the early seventies with DPs like Gordon Willis who shot THE GODFATHER. Hope this helps. |
|
Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
|
Post by Flynn on Sept 15, 2017 22:23:58 GMT
I wasn't sure where to post this question, so I thought I'd put it here, since classic film enthusiasts might have a better understanding of the techniques of film photography. Does anyone here know how exposure works in moving picture photography? What I'm wondering about is how one handles shutter speeds in moving-picture cinematography. If I take a still picture in low light, for example, I might have to adjust a shutter speed to be 1/30 or 1/15 of a second. So, in a medium where one needs a constant 24 frames per second, how is exposure compensated for? It can't be with shutter speed or aperture, so how does exposure work? You have to adjust the f-stop to a wider aperture to let in more light, and possibly use a wider angle lens, both of which, of course, affect depth of field. It also depends upon the ASA or speed of the film stock you're using. The higher the speed, the less light you would need, so the depth of field could be manipulated by using longer lenses and lower f-stops. Higher ASA stocks began to be used regularly in the early seventies with DPs like Gordon Willis who shot THE GODFATHER. Hope this helps. Thanks. I'm a little surprised to hear that it works the same way as in still photography, I mean, film is film, so it shouldn't be too surprising, but I'm thinking of the apartment scene in LAURA, where McPherson turns on lights in a fairly dark room. I wonder how the cinematographer compensated for the sudden addition of light. There aren't any cuts, and the depth-of-field remains constaint. I have no experience with moving film cameras, so this is just something that always made me curious. |
|
|
|
Post by Doghouse6 on Sept 15, 2017 23:10:34 GMT
You have to adjust the f-stop to a wider aperture to let in more light, and possibly use a wider angle lens, both of which, of course, affect depth of field. It also depends upon the ASA or speed of the film stock you're using. The higher the speed, the less light you would need, so the depth of field could be manipulated by using longer lenses and lower f-stops. Higher ASA stocks began to be used regularly in the early seventies with DPs like Gordon Willis who shot THE GODFATHER. Hope this helps. Thanks. I'm a little surprised to hear that it works the same way as in still photography, I mean, film is film, so it shouldn't be too surprising, but I'm thinking of the apartment scene in LAURA, where McPherson turns on lights in a fairly dark room. I wonder how the cinematographer compensated for the sudden addition of light. There aren't any cuts, and the depth-of-field remains constaint. I have no experience with moving film cameras, so this is just something that always made me curious. When I first read your query this morning, I was hoping spiderwort would jump in. I refrained from commenting then, as my knowledge is both scant and second-hand (having worked only in post, and then, only in clerical/administrative capacities). But conceptually, perhaps it helps to remember that motion picture photography is actually still photographs: 24 of them per second. What the DP does is set illumination and exposure for hundreds of photographs in succession rather than for a single one. Would that be fair to say, spider (if you're monitoring this thread)? |
|
|
|
Post by koskiewicz on Sept 16, 2017 0:24:05 GMT
...I've taken thousands of still B&W photos. The post indicating film ASA, shutter speed and aperture is spot on. One additional factoid is that the faster the film (ASA) the grainier the result...
|
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 16, 2017 1:52:09 GMT
Thanks. I'm a little surprised to hear that it works the same way as in still photography, I mean, film is film, so it shouldn't be too surprising, but I'm thinking of the apartment scene in LAURA, where McPherson turns on lights in a fairly dark room. I wonder how the cinematographer compensated for the sudden addition of light. There aren't any cuts, and the depth-of-field remains constant. You're welcome, Flynn. As to the scene in LAURA, I'll address the topic in general: The DP sets lights for the darkness to be visible enough for that part of the scene. At the same time he also lights for the room when the lights are turned on. When the actor is in the darkness we only see the lighting the DP set for the dark part of the scene. But when the actor turns the lights on, the lighting the DP set for that part of the scene is turned on in sync with the actor hitting the switch. It's a two-step process done with a dimmer board. Hope this makes sense. |
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 16, 2017 1:58:49 GMT
. . .conceptually, perhaps it helps to remember that motion picture photography is actually still photographs: 24 of them per second. What the DP does is set illumination and exposure for hundreds of photographs in succession rather than for a single one. Would that be fair to say, spider (if you're monitoring this thread)? Yes, Doghouse. There are negligible consequences due to a two frame pull-down when shooting and projecting, but I think for all intents and purposes, it's fair to say what you've said. |
|
|
|
Post by Doghouse6 on Sept 16, 2017 3:11:30 GMT
You're welcome, Flynn. As to the scene in LAURA, I'll address the topic in general: The DP sets lights for the darkness to be visible enough for that part of the scene. At the same time he also lights for the room when the lights are turned on. When the actor is in the darkness we only see the lighting the DP set for the dark part of the scene. But when the actor turns the lights on, the lighting the DP set for that part of the scene is turned on in sync with the actor hitting the switch. It's a two-step process done with a dimmer board. Hope this makes sense. Again, I was hoping you'd weigh in, holding in abeyance my theory based on limited understanding (basically, that no compensation was required for the reasons you explained; as I recall, the shot in question was a "master" type long shot - rather than a Gregg Toland-style "deep focus" one - with nothing significant in the foreground, but with full depth of field encompassing the entire set at both levels of illumination). Considering that one happened to bring to mind another shot in Laura, this one rather the opposite in focal and lighting design: a closeup of Gene Tierney in Andrews's interrogation room in which the exposure is set for the general stage lighting, but in which Tierney's face "blooms" from the overexposure when Andrews turns on the practicals (the harsh spotlights aimed at her from the desk). The shot - and the effect - is one of my favorites in the film: a starkly "noir-ish" one that stands out from the glossy yet restrained elegance that Preminger and DP Joseph LaShelle employ in most of the film's setups. |
|
Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
|
Post by Flynn on Sept 17, 2017 3:02:52 GMT
Thanks to everyone who responded. I sincerely appreciate your attention to my question. I was a little surprised at the answer, but I guess it makes sense. I didn't expect exposure in moving film photography to be so similar to still photography. Here's what I understand so far.
Film speed is set. Whatever ASA film speed that is in the camera isn't changing with a sudden change of light (barring a cut to different film stock).
In moving film, shutter speed is also set at 24 fps.
With both of those set, aperture is the only element of the exposure triangle that can respond to change. So, I guess if someone turns on a light in a room, the aperture would have to be manually adjusted to compensate. I would think depth-of-field would also change in such situations, but I guess it's very subtle. Maybe two stops of light wouldn't change DOF that much, a few feet, maybe, depending on the point of focus.
I'm guessing that there's something I'm not thinking of as well, like maybe that motion film cameras are bigger and thus let in more light than a little 35mm still film camera.
This whole question actually got me to thinking about how slow 24 fps actually is. It's not easy to take a still picture at that speed without a tripod, and so it makes me wonder how handheld movie cameras work without getting a lot of camera shake. Probably has to do with the lenses, I guess.
In any case, if there's anything anyone wants to chime in about, please feel free to do so. Otherwise, I'd like to thank everyone for the interest.
|
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 17, 2017 14:49:23 GMT
Thanks to everyone who responded. I sincerely appreciate your attention to my question. Glad to be of help, Flynn. And you have everything right except for one thing. The DP lights the dark and the light parts of the scene so that the aperture does NOT have to be adjusted; that would be a virtual impossibility anyway - barring, of course, doing it intentionally for some special effect. The change in depth-of-field would be obvious, to say nothing of the fact that the camera assistant wouldn't be able to time it perfectly. As hard as it is to grasp, the f-stop is set and works for both parts of the scene. It's all in the lighting the DP does for both in the beginning. (I know this may be hard to fully grasp; I can only tell you that it's true.)
As for the cameras being bigger, that makes no difference as to the amount of light received. 16mm cameras and even super8 and 8mm let in all the light their aperture will allow. F-stop changes and lens size choices in 35mm and 16mm (where you have those options) are the only ways to regulate or vary that.
As for hand-held, yes the wider angle the lens is the less shake you get, though you will get some (not a flutter, as you may be thinking - just a shake from the operator's handling). If you want no shake at all, then you have to use a steadicam or put it on a tripod - or, as I've seen, have a great operator, using a wider angle lens, who can hold the camera as steady-as-a rock. That's not easy to do and not done often or for long. Sometimes the hand-held look is intentionally shaky (i.e. "shaky-cam" - if motivated I find it interesting; if not I hate it).
Again, I hope this helps. I've looked for sites on the web to give you more information, but everything now is about digital. The two are growing closer in terms of lens options, but there are so many other variables that would just muddy the waters when it comes to the questions you're asking.
|
|
Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
|
Post by Flynn on Sept 17, 2017 15:19:46 GMT
Thanks, Spiderwort. Regarding camera shake, I should have specified that what I was referring to is the fact that if I'm shooting something with a shutter speed at 1/30th of a second, both my subject and I have to be still. Otherwise, I will get motion blur. So, if a moving film camera shoots something with a shutter speed at 1/24th of a second, why doesn't motion blur occur when people are doing normal things like walking (or doing anything other than remaining still)? Sorry to be so dense on this. I appreciate your very helpful comments.
Maybe I should ask that "Filmmaker IQ" guy on YouTube to do a video on exposure and shutter speeds in film photography.
|
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 17, 2017 15:48:59 GMT
You're welcome Flynn. I don't know the precise answer to this question. I've been going off of my own experience with 35mm film photography and decades of film directing. But you've got me with this one. I have a DP source for the answer, and I'll let you know after I talk to him. |
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 17, 2017 23:03:17 GMT
Flynn I talked to my friend and he explained that (with the 2 frame pull down in the camera) you're actually shooting at a shutter speed of 1/48th of a second. But unlike with a still camera, in which you could see movement at that shutter speed and therefore would want the camera and the subject to remain still, in a film you actually want that movement captured on the frames as they flow, because it augments the movement perceived in the camera and then later on the screen. I know this sounds counter-intuitive, but that's how it works. He said if you didn't have that, if you shot at too high a shutter speed (which can be done under certain circumstances, but isn't desirable), it would actually make things look jerky when projected. I hope this answers all your questions. And thanks for enabling me to learn something new, too. Oh, and he told me that for the light change we discussed, he would light for the brightest first, and then for darkest (the brightest being the standard against which the darkest is set).
|
|
|
|
Post by Doghouse6 on Sept 18, 2017 0:20:58 GMT
Flynn I talked to my friend and he explained that (with the 2 frame pull down in the camera) you're actually shooting at a shutter speed of 1/48th of a second. But unlike with a still camera, in which you could see movement at that shutter speed and therefore would want the camera and the subject to remain still, in a film you actually want that movement captured on the frames as they flow, because it augments the movement perceived in the camera and then later on the screen. I know this sounds counter-intuitive, but that's how it works. He said if you didn't have that, if you shot at too high a shutter speed (which can be done under certain circumstances, but isn't desirable), it would actually make things look jerky when projected. I hope this answers all your questions. And thanks for enabling me to learn something new, too. Oh, and he told me that for the light change we discussed, he would light for the brightest first, and then for darkest (the brightest being the standard against which the darkest is set). I'm unfamiliar with the terminology "2 frame pull down." I'm aware of "3:2 pull down" (employed in telecine to compensate for the differing frame rates of film and video), but this one puzzles me. I love learning new things (of which you're a reliable source), which sometimes appear to conflict with my supposed understanding of what I thought I knew. Huh? So here's what I mean: although motion picture film advances at a rate of 24 fps, each frame can't remain stationary in the gate for the full 1/24th of a second, as the mechanism must allow time between each exposure for advancement to the next frame; hence, a normal 180° angle of the rotary shutter results in an exposure of 1/48th of a second, with the film then advancing to the next frame (while the shutter is in the "closed" position) during the remaining 1/48th of a second. Now, am I off-base on that, or is "2 frame pull down" merely a term economically-coined to describe that operation (rather than a literal one indicating that the sprockets actually advance the film 2 frames at a time)? And I hope I've at least posed those questions in an intelligible way. |
|
spiderwort
Junior Member
@spiderwort
Posts: 2,544
Likes: 9,340
|
Post by spiderwort on Sept 18, 2017 0:47:12 GMT
So here's what I mean: although motion picture film advances at a rate of 24 fps, each frame can't remain stationary in the gate for the full 1/24th of a second, as the mechanism must allow time between each exposure for advancement to the next frame; hence, a normal 180° angle of the rotary shutter results in an exposure of 1/48th of a second, with the film then advancing to the next frame (while the shutter is in the "closed" position) during the remaining 1/48th of a second. Now, am I off-base on that, or is "2 frame pull down" merely a term economically-coined to describe that operation (rather than a literal one indicating that the sprockets actually advance the film 2 frames at a time)? Yes, Doghouse, that is exactly right. No literal advancing of two frames at a time, but one pulled down, held, then moved on. Good for you for knowing that. Oh, what an interesting conversation all of us have had on this thread, thanks to Flynn! It's been great. |
|
Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
|
Post by Flynn on Sept 18, 2017 0:53:38 GMT
spiderwortThank you so much. Yeah, that actually makes a lot of sense. I wasn't taking into account the need for each frame to stop (which I knew it did; I just wasn't thinking about it), which would necessitate an increase shutter speed. I was aware of the awkward visual appearance of high shutter speeds, so I was having trouble reconciling how it all works. I understand it now. As for exposure, I had never realized how much a cinematographer was contrained by the amount of light, given that ISO and shutter were already set. I'm guessing that moving picture films are designed to have greater latitude when filming so that a cloud passing over doesn't ruin a scene by causing an underexposed moment. In still photography, it's easy to change the shutter or aperture to compensate, but in moving film, you'd want a film that wasn't so picky. Thanks for all your answers.
|
|
|
|
Post by Doghouse6 on Sept 18, 2017 1:14:08 GMT
Yes, Doghouse, that is exactly right. No literal advancing of two frames at a time, but one pulled down, held, then moved on. Good for you for knowing that. Oh, what an interesting conversation all of us have had on this thread, thanks to Flynn! It's been great. Thank you, thank you! And yes, it has been. Getting down into the "nuts and bolts" is endlessly fascinating. So yes, thanks to Flynn for bringing it up, to you for your expertise and patience, and to petrolino and vegalyra for their interest and attention. |
|
Flynn
Sophomore
@flynn
Posts: 515
Likes: 270
|
Post by Flynn on Sept 18, 2017 1:26:56 GMT
For fun, I looked up the specs for Vision3. Here's what I found on the spec page:
"Like other films in the VISON3 Film family, VISION3 50D Film features unrivaled highlight latitude, flexibility in postproduction, and proven archival stability. The expanded dynamic range allows for increased creative control in the extremes of exposure, especially high contrast daylight exteriors. Advances in grain and sharpness along with increased exposure latitude also make this film ideal for recorder output."
I'd say that high latitude is definitely a selling point of the film.
|
|
|
|
Post by Doghouse6 on Sept 18, 2017 1:37:27 GMT
For fun, I looked up the specs for Vision3. Here's what I found on the spec page: "Like other films in the VISON3 Film family, VISION3 50D Film features unrivaled highlight latitude, flexibility in postproduction, and proven archival stability. The expanded dynamic range allows for increased creative control in the extremes of exposure, especially high contrast daylight exteriors. Advances in grain and sharpness along with increased exposure latitude also make this film ideal for recorder output." I'd say that high latitude is definitely a selling point of the film. Here's one for you, Flynn - a relatively recent development, I gather - that relates directly to your original query:
cinefade.com/#introductionTheir demo video shows what looks like an Arriflex digital camera (I didn't know Arri made them), but their site says it's adaptable to film cameras. |
|
