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Why not increase shutter speed? Why use NDs? (Seriously)
  • This is something I've wondered ever since getting into digital cinematography. Why are people so attached to the 180 degree shutter rule (which truly is an artifact of the film era), that they insist on keeping the shutter speed at 1/50 and throwing another piece of glass in front of their lens? Having broken my ND filter and not bothering to replace it, opting instead for managing shutter speed to expose correctly, I have come to the conclusion that I am getting better image quality now than I ever did at 1/50 shutter speed with an ND filter.

    There are added benefits, besides eliminating the need for an ND, which will inevitably degrade image quality. For one, is an apparent reduction in rolling shutter - which stands to reason, as the sensor read-out is much faster with a faster shutter speed. Another added benefit is that footage recorded at faster shutter speeds plays much more nicely with Twixtor. I don't use Twixtor often, but it's nice to know that if I catch something on my camera that I want to see in ultra slow-motion, I haven't crippled myself with excessive motion blur. On the other hand If I ever feel that my image is lacking motion blur, I just add it in post.

    I know that the 180 degree shutter rule is one of the most sanctified laws of filmmaking, along with the 24fps frame rate. I know that people go to great lengths to keep their shutter speed at 2x their frame rate. I just don't really understand why, given that it's not a physical requirement of modern digital cameras.

  • 120 Replies sorted by
  • I'm not sure if this is a real thread or not. I mean you know what motion blur is right and how doing this will drastically change that.

  • I do, and it is a serious question. As I said, if I ever feel that my footage is suffering from a lack of motion blur (which honestly I rarely do), I just add it in post.

  • Also get the feeling you are fishing for an argument. Good NDs don't degrade image quality or degrade to a negligible level. Why use 180 degree rule... because motion blur is something we see with our eyes and the camera needs to mimic that, otherwise it looks unnatural and like a strobe effect. Would you shoot a quiet conversation scene like it was saving private Ryan...

  • Not really fishing for an argument. Sorry if I came off as overly aggressive in my original post. I'm trying to understand this. Is it really just about motion blur? Is software motion blur inadequate?

    Edit - here are the pros and cons as I see them:

    180 Degree Shutter Pros: "Filmlike" motion-blur recorded in camera, Tried and tested method

    180 Degree Cons: No control over motion-blur in post. It is what it is, Requires carrying around an ND set, or a variable ND, which affect image quality to varying extents, More rolling shutter on most DSLR and low-budget interchangeable lens cameras.

    Exposing with shutter Pros: Convenience, cost savings, and IQ improvement of not needing an ND set, Control over motion-blur in post, Less rolling shutter, Better results in Twixtor for artificial slow-mo effects,

    Exposing with shutter Cons: Getting motion blur requires an extra step in post, People might think you're not a serious filmmaker.

    Please feel free to correct me if I'm wrong in my thinking. I am not looking for an argument, I'm looking for someone who can explain to me why I'm wrong.

  • Software is never a better solution to nailing it in camera.

  • @RatLabProductions: I do recognize that point. But on the other hand, couldn't the case be made that since you can add motion blur in post easily but reducing it is very difficult, you should shoot for minimal motion blur and allow yourself the freedom to manipulate it in post?

    It seems like a similar argument in favor of or against shooting in a flat picture mode. Sure, there are situations when you know exactly what you want, and you can nail it in camera -- dial in the shutter speed, contrast, saturation, etc that you need for finished output. But more often, I find myself enjoying some latitude to manipulate these elements in post, and that does include motion blur.

  • Sure, there are situations when you know exactly what you want, and you can nail it in camera -- dial in the shutter speed, contrast, saturation, etc that you need for finished output. But more often, I find myself enjoying some latitude to manipulate these elements in post, and that does include motion blur.

    Until you are doing it just for fun, you must do as much as possible on set. As otherwise you are spending your time and spending money.

  • thats a good arguement. whats quicker, wacking on an ND filter or rendering for motion blur?

    i guess you are not wrong if you think it is working for you, just don't expect others to follow your logic thats all =)

  • It's very unconventional, but who are we to tell you what is right and wrong for your personal workflow?

    'Personal workflow' being the operative words here, because if you did this on a real shoot, offsetting camera operator work to the post production team is a sure-fire way to get sure-fired.

    FILM SET - MORNING

    The DIRECTOR and SANGYE huddle in the video village over a reference monitor reviewing the recently shot footage. The Director shoots a glare at Sangye.

              SANGYE
    

    Hey, it's okay, just fix it in post.

              DIRECTOR
    

    Hey, it's okay, just go get me a fresh hot coffee, then dump it on your face and leave the set.

    FADE TO BLACK

  • i hardly think this dude has done any post-blur to real footage, because getting it right, even when only one performer is (for example) running from one side of the frame to the other side, is a pain in the ass, as you must use masks to get a convincing effect on the moving parts, specially in the arm and leg that gets behind the torso from the camera point of view, using automatic detection doesn´t always work, doing this for a longer proyect would be just absurd... for a short though, or even a tv advertising but longer than 2-3 minutes just plain absurd

  • I mean come on man, you really can't be serious. I mean it's filming 101 and you know it. This is one of the more absurd threads I've seen in a long time. It really feels like you're trolling here.

    So to sum things up, looks like you got your answer from multiple people.

  • You'd be fine if you were filming the Digital Bolex shipping department...

  • Edit - Lol @spacewig, indeed.

    Of course I would never do this on a larger production without approval. It's a convention, and having conventions serves a purpose. But I stand by what I've suggested here. I'm not out to convince anyone, I only want to enrich my own understanding.

    And myself, I am not convinced. Motion blur is in my mind a distortion of reality. Distortions of reality are appropriate for and indeed commonplace in film and the visual arts, but they should be controlled. That kind of control is best exercised in an editing booth. I'd rather record the most accurate & unbounded representation I can, in camera, and let the distortions and constraints come after the fact. I've generally had good results using auto detection, but I also haven't shot a lot of very fast moving subjects this way.

    I wonder whether this might be an artifact of current technological limitations. Shooting fast moving subjects at 24P with a high shutter speed does lead to a distinct effect, as seen in Saving Private Ryan. If you have a tank shell in one frame in the top left corner of the screen and by the next frame it's already landed in the bottom right, without motion blur, that's a problematic effect. But that has more to do with the frame rate than with the shutter speed. With the UHD standard being set at 120p, motion blur will become less of a problem and maybe less important, as each individual frame is that much more similar to adjacent frames.

    edit #2 - I feel like this thread isn't really going in the direction I intended. An important reason for my argument in favor of shooting at higher shutter speeds was how it seems to benefit rolling shutter. Tomorrow I'll shoot a quick test and upload it. If nothing else, I'd pick reduced "jello" over slightly staccato motion any day.

  • I had the same question a long time ago @Sangye. What I've been reading is to do it in post is very difficult and long. I would love to see some convincing footage with proper 24p motion blur added in post.

  • @Sangye Screw all this filming 101 shit. I say ...To each his own. If you find that you like to add post motion blur to the look you want, then go for it. For me finishing it in camera is rarely done these days no matter what camera I use. We all need our own way to be creative, following the rules isn't always the best way. But they are nice to fall back on. My only concern with high shutter speeds and non 180 degree angles is that they may miss some of the action in fast moving objects so be careful of how far you push it.

  • @rigs Nice, let's just throw all the basic fundamentals out and start over. There's reasons why things are done the way they are. Yes, there's times when you go against the grain but why add to a workflow with heavy post work? And thanks for telling me to pretty much piss off.

  • Hey hey hey. I don't think anyone told you to piss off, I think rigs was only suggesting that rules exist as much to be followed as to be broken. I agree, though obviously conventions serve an important purpose in the industry. I also found your points, @vicharris, useful in reexamining my own. I know I argued for a rather controversial point, but I don't want to see this turn into a flame war.

  • I think this question is valid and I have being done this question to myself since long time and I found myself the answers and solutions I would use:

    I can say about examples I saw and about my own taste:

    In some action scenes like Rambo in the forest, like cars crashing, I perceived that the director used high shutter speed to avoid the motion blur and allow people to see things more sharp in fast actions.

    Also in some slow motion scenes (without twixtor, just overcranking) I also saw that the shutter was higher than 180 degrees to avoid motion blur also.

    In panoramic scenes, when camera describes a location, I just hate 180 degrees shutter, because it just blurs things that I would like to see better, this is my personal taste, but most panoramic scenes are done in 180 shutter, I do not like it. If there was someone walking, the 180 shutter would be ok, because the people walking would be sharp and background would blur.

    I like 180 shutter when filming people in dialogs, because in dialogs the faces are more static even if people is walking, so the background will blur and the face will be ok.

    low light situations will need lower shutter speeds, 1/30, 1/25, 1/24, so I would be carefull with camera movements and people movements, or let them move and deal with the blur, as an aesthetics result.

    the fader / variable nd does not hurt the image so much. and if you use the tiffen or genus brands they are great quality. I am using a fotga from ebay which is cheap and good enough. I am learning to deal with the limitations. A small decrease in resolution, a small amount of noise, a limited dynamic range... if not disturbing, it is ok. Pursuing perfection can make you always unhappy.

    I will never add motion blur in post, this is a decision I will do in the camera recording moment, a director decision in the moment of capture the image.

  • It's funny but often some of the coolest things get started by mistakes or by experimentation and then being brave enough to let the public decide if they like it. This is the beauty of living IMO. Science, Art and Music have all been progressed by such adventurous spirit.

  • While I think Sangye meant he want's to decide the how much motion blur a image shows by adjusting the shutter speed for creative reasons and get rid of the ND's, which I think are valid points, adding motion blur in post is NOT!

    You simply cannot add real motion blur in post. While you may be able to fake it very convincingly (hell of a lot of work!), the image will always look weird. I don't mean obviously weird, but the viewer will know somethings off.

    I come from a CG/VFX background and believe me, not even with all the extra image channels we can render out from 3d software packages (depth, motion vectors and whatnot), you can beat a correctly rendered motion blur (at rendertime) with something done in post in NukeX.

    With real footage you even run into more problems, because you lack all the extra information CG can provide.

    So adjust the shutter speed to your liking, from weirdly long to hyperrealistic nonexistent, but please: Don't try to add motion blur in post unless it serves a narrative purpose (Scott Pilgrim anyone :) because it'll always look fake.

  • There are pretty good measures for adding motionblur in post. Just like the all-knowing warp-stabilizer in AE you've got simular algorithms for motionblur - where the program/plugin analyze the entire shot pixel by pixel and then add motionblur on the highest contrast spots/pixels which usually give great results as there is no need for keyframe animation or any old method like that. Reelsmart motionblur for NukeX/AE is a pretty good start, and it produces really nice results.

  • if your output is going to be 50P, does the 180 shutter rule still apply? I would have thought that given a higher output framerate it would be difficult for the eye to determine the difference in shutter speed, unless of course it was less than 180 shutter.

  • I remember a friend of mine (who is very into movies but knows nothing about film techniques and 180 shutter) who noticed and appreciated very much the "strobing" effect he saw in the movie 23 Days Later

  • I've done tests with open gate (aka 360 degrees shutter) for 50 fps and it looks quite nice. So, 1/50th of a second seems to be similar to our natural perception. We use artificial motion blur sometimes for chroma keying, shooting sharper edges and blurring over the keyed footage later. Even with a good software like RSMB you get smearing artifacts on complex motion, I'd never do that if its not needed. Motion blur from camera is much better and takes less time. The artifacts are uglier than any good ND good be.