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    #11
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    Projection is 24fps, period. Just because the frame is flashed twice, doesn't mean it's showing more frames per second. The film runs through the projector at 24 frames per second. Flashing the frame two (or three times) does absolutely nothing to change the feeling of motion; instead it is to even out the flicker that comes from bright frames being projected and then the shutter being held dark for a long time. By using a two- or three-bladed shutter they can even out the flicker.


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    #12
    Senior Member j's Avatar
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    > I've stumbled upon an article about the 180 degree rule and why it's important to respect this rule as long as we don't have particular needs.

    Link?


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    #13
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    So how do I use an exposure meter and obey the 180 deg rule?


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    #14
    Senior Member GrahamH's Avatar
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    To obey the 180 degree rule, set your shutter speed to one half of the frame rate (e.g., 1/48th or 1/50th if you are shooting 24fps).

    Then use your light meter to determine what aperture is required for correct exposure at that shutter speed.

    If you don't like the aperture value that is required, adjust your ISO, lighting and/or amount of ND filtration ... while leaving the shutter speed unchanged.
    ---------------------------------------------------------------------------------------------------------------------
    Cameras: AF-100, G7 (formerly G6, GH2, HMC-40) -- Lenses: Lumix, legacy Nikons with Speedbooster -- NLEs: Premiere and AfterFX CS6 and CC on PC


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    #15
    Senior Member JMtheDP's Avatar
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    I'll try and help here by giving example of a scenario and solution.

    Generally we like to decide stop in advance and stick to that stop for a consistent "look". The same reason (one of many) we use the same shutter speed.

    Outdoors, I like to shoot around T4. My lenses are pin sharp there. There's just enough DoF to both look nice and give my focus puller a chance.

    I'll have my lightmeter set to 25fps (I'm in Europe) and, say, 500 ISO. My lightmeter will say something like T16 (possibly a lot more). Now it is telling me I need T16 to get the right exposure. But I want to shoot at T4. So work out the stops difference.

    T4 T5.6 T8 T11 T16

    I can see that my lightmeter is telling me there is four stops of exposure I need to get rid of. So I will use an ND 1.2. Then my exposure will be correct. Hope that helps.
    James Martin, UK-based DoP
    www.jamesmartindop.com
    Sony F65, ARRI/Zeiss Master Primes, ARRI Alura Zooms
    Formerly: F900, F35, Zeiss Standard Speeds, Illumina S35s...


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    #16
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    Thanks, so ND is the extra variable


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    #17
    Senior Member JMtheDP's Avatar
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    Yes.

    And I'm not sure if anyone answered the OP's question as to what ND actually is... it is a filter (usually glass, often built-in to some cameras) which darkens the image without affecting the colour balance in any way. It stands for Neutral density.
    James Martin, UK-based DoP
    www.jamesmartindop.com
    Sony F65, ARRI/Zeiss Master Primes, ARRI Alura Zooms
    Formerly: F900, F35, Zeiss Standard Speeds, Illumina S35s...


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    #18
    Steak Knife Member David G. Smith's Avatar
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    So, what is the "180 degree rule"? I shot a lot of film but the widest shutter angle I ever worked with was 170 degrees. Now, with digital acquisition, I pretty much stick to 1/48th a second shutter speed and use lighting, aperture settings, gain (Or ISO settings) and ND filtration to control exposure. I have done some casual experiments with shutter speed changes to affect exposure but found it to not to be to my liking. Am I missing something?
    "The enemy of art is the absence of limitations"
    -Orson Wells.

    "To me the great hope is... people that normally wouldn't be making movies will make them and suddenly some little fat girl in Ohio will be the new Mozart and will make a beautiful film using her father's camera-corder and the "Professionalism" of movie making will be destroyed forever and it will finally become an art form."
    -Francis Ford Coppola.


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    #19
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    Quote Originally Posted by David G. Smith View Post
    So, what is the "180 degree rule"? I shot a lot of film but the widest shutter angle I ever worked with was 170 degrees. Now, with digital acquisition, I pretty much stick to 1/48th a second shutter speed and use lighting, aperture settings, gain (Or ISO settings) and ND filtration to control exposure. I have done some casual experiments with shutter speed changes to affect exposure but found it to not to be to my liking. Am I missing something?
    I think people are getting confused over the "180 degree rule"
    There is this "180 degree rule"


    and this "180 degree rule"

    http://tylerginter.tumblr.com/post/1...ive-it-love-it


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    #20
    Sound Ninja Noiz2's Avatar
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    Quote Originally Posted by Barry_Green View Post
    Projection is 24fps, period. Just because the frame is flashed twice, doesn't mean it's showing more frames per second. The film runs through the projector at 24 frames per second. Flashing the frame two (or three times) does absolutely nothing to change the feeling of motion; instead it is to even out the flicker that comes from bright frames being projected and then the shutter being held dark for a long time. By using a two- or three-bladed shutter they can even out the flicker.
    That is not entirely true. The brain perceives the second frame as being split between the first film frame and the second film frame. So while in the real world yes there is no change in the second flash, humans "see" it as an in between frame and it does add to the smoothness of the motion.

    Video though is a totally different beast. It has no "black" between frames, which also helps hide motion issues in human brains, and it paints the image down the screen instead of painting it across the screen. Both are so fast that it may not make a big difference but film is going "with" the most common motion (side to side) and video is going at odds to the motion. So while film would tent to smear the image the same way as motion blur, video is creating a "rolling shutter" type distortion.
    Cheers
    SK


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