vitaluminosa
Active member
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Shutter Speed
- Thread starter vitaluminosa
- Start date
Kevin Briggs
Well-known member
MDKfilms
Well-known member
Well, if you set your video cameras shutter speed to lets say 1/250th, you get the very popular stacatto visuals that are used in alot of music videos. That is just one use, many many more. As for slow motion, consumer cams with the exception of the HVX200, are not very good at it, yet!
Remember that shutter speed isn't equivalent to frames-per-second. So shooting at a shutter speed of 1/500 will cut down a great deal on the amount of light entering the camera, and will give movement a very rapid, jerky movement (the popular example is the opening of Saving Private Ryan), but it's not like you're shooting more frames than usual. The best you can do on the DVX for instance is to shoot 60i (which gets you 60 motion samples a second, albeit at half-resolution) and then slow it down in your editor as per Barry Green's book. At 60i you would want to shoot with a shutter speed of 1/120 for the cleanest possible slow motion.
Kevin Briggs
Well-known member
vitaluminosa said:
I think setting the shuuter speed as fast as you can looks kind of cool, but like others said it reduces the light that enters the camera. I believe by 1 f-stop for every doubling of the shutter speed. Most sports photographers/videographers shoot at 1/250 if there is enough light to get a crisp shot. Read on some photography forums about apature. You cannot change your shutter speed in post. 1/4 shutter = lots of light, and extremely blurry whith any motion at all. 1/2000+ shutter = a huge reduction in light, but extremely crisp footage. A praticle example of using 1/4 would be filming a slug at dusk on a tripod. Reasons... the slug will move slow enough to not make the footage suffer from the extra blur and you will get the extra light from the shutter staying open .25 seconds for extra light at dusk. A praticle example of using 1/2000 is outside on a super sunny day at Nascar. Reasons...It will most likely be bright enough to couteract the low light from the fast shutter, and when the cars go by at 200+mph you will be able to see them much more clearly than you would at your regular 1/48 for 24fps or 1/60 at 30 fps. One more thing... your shutter speed will not help you with slowing your footage down or speeding it up.
-Kevin
Shutter speeds control motion blur. Used often when taping sports, a high speed shutter setting allows each frame of video to be crystal clear. So how does this work?
On a still camera the shutter speed is a mechanical adjustment and simply controls how quickly the cameras shutter opens and closes.
However, with video the adjustment is electronic since a video camera does not have a true mechanical shutter that opens and closes.
What happens is your camcorder is changing the length of time light is allowed to build a charge on the cameras ccd imaging chip.
So obviously, the higher the shutter speed the lower the exposure time, requiring more light.
With a camera like the DVX or any that allows you true manual control of the iris the shutter setting takes on an additional use as another tool to control exposure. For instance, if you want that cinematix shallow depth of field and you're outside on a bright sunny day and your iris is at its smallest setting creating an almost infinite depth of field. Then you can up the shutter speed. This will allow less exposure time on the CCD's creating a darker image thus allowing you to open the iris creating a shallower depth of field.
On a still camera the shutter speed is a mechanical adjustment and simply controls how quickly the cameras shutter opens and closes.
However, with video the adjustment is electronic since a video camera does not have a true mechanical shutter that opens and closes.
What happens is your camcorder is changing the length of time light is allowed to build a charge on the cameras ccd imaging chip.
So obviously, the higher the shutter speed the lower the exposure time, requiring more light.
With a camera like the DVX or any that allows you true manual control of the iris the shutter setting takes on an additional use as another tool to control exposure. For instance, if you want that cinematix shallow depth of field and you're outside on a bright sunny day and your iris is at its smallest setting creating an almost infinite depth of field. Then you can up the shutter speed. This will allow less exposure time on the CCD's creating a darker image thus allowing you to open the iris creating a shallower depth of field.
Ok, stupid question then, I do understand that bumping the shutter speed up allows for a larger aperature and shallower depth of field. Then why is 1/48 or 1/60 considered "standard?" Should I be trying to shoot my features at 1/48 using filters to bring the aperature open and my sports wide open and fast shutter?
khmuse
Tech Guru
Keep in mind that the shutter angle of a rotary gate film camera, combined with the frame rate (fps) determines the duration that the film frame is exposed, just as in a progressive digital video camera (like the DVX) the frame rate and shutter speed determine the duration that the CCD is exposed.
At 24 fps, a shutter speed of 1/48th of a second is equivalent to a shutter angle of 180 degrees. At the same frame rate, a shutter speed of 1/60th of a second is equivalent to a shutter angle of 144 degrees. These two equivalent angles cover nearly all the usual shutter angles used in motion picture film cameras, so hence the use of the term "standard".
Using a shutter speed of 1/48th of a second will gain you a bit more light which can be useful if you are working in a lower illumination situation (its usually a better option than adding gain as you won't encounter additional noise) but it does add a bit more motion blur than 1/60th of a second would.
The gain in light is small, but can be enough in certain situations:
Gain = 20*log(A/B) = 20*log(60/48) = 20*log(1.25) = 20*.0969 = 1.93 dB
Even slower shutter speeds (1/36th of a second) will gain additional light, but with ever increasing amounts of motion blur.
Its all a balanced compromise that can be used to your advantage if you understand the trade offs and considerations.
At 24 fps, a shutter speed of 1/48th of a second is equivalent to a shutter angle of 180 degrees. At the same frame rate, a shutter speed of 1/60th of a second is equivalent to a shutter angle of 144 degrees. These two equivalent angles cover nearly all the usual shutter angles used in motion picture film cameras, so hence the use of the term "standard".
Using a shutter speed of 1/48th of a second will gain you a bit more light which can be useful if you are working in a lower illumination situation (its usually a better option than adding gain as you won't encounter additional noise) but it does add a bit more motion blur than 1/60th of a second would.
The gain in light is small, but can be enough in certain situations:
Gain = 20*log(A/B) = 20*log(60/48) = 20*log(1.25) = 20*.0969 = 1.93 dB
Even slower shutter speeds (1/36th of a second) will gain additional light, but with ever increasing amounts of motion blur.
Its all a balanced compromise that can be used to your advantage if you understand the trade offs and considerations.
Kevin Briggs
Well-known member
Hey Khmuse,
In film cameras is the shutter an actual moving part? Does it actually open and close 48/60/120/250 etc... times per second? Also what does the angle have to do with it? Does the angle of the shutter dirrectly relate to the shutter speed? What is the shutter made out of...does it matter?
Just curious.
-Kevin
In film cameras is the shutter an actual moving part? Does it actually open and close 48/60/120/250 etc... times per second? Also what does the angle have to do with it? Does the angle of the shutter dirrectly relate to the shutter speed? What is the shutter made out of...does it matter?
Just curious.
-Kevin
In a still (film camera) a shutter is a mechanical device that opens and closes like a curtain for each exposure. In a motion film camera, the shutter is a wheel with a chunk cut out of it that rotates.
I think it is probably fair to say that varying too far from 1/48 or 1/60 shutter is going to be perceived as an effect or stylistic choice. To use a well worn example, all of the action scenes in Saving Private Ryan switch to a much higher shutter speed, but switches back when it is over. It would probably make you hurl to watch a 3 hour movie shot in SPR Action mode
I think it is probably fair to say that varying too far from 1/48 or 1/60 shutter is going to be perceived as an effect or stylistic choice. To use a well worn example, all of the action scenes in Saving Private Ryan switch to a much higher shutter speed, but switches back when it is over. It would probably make you hurl to watch a 3 hour movie shot in SPR Action mode
MDKfilms
Well-known member
Sorry, don't want to step on any toes, but yes, the shutter in a film camera is an actual moving part, usually made out of aluminium, and is mirrored, and the usual opening is 180 degrees. Film cameras do not deal with shutters the same way a video camera does, the shutter in a film camera can be adjusted to different angles so that less light gets to the film. This variable shutter in a film camera is a mechanical device, but in a video camera there is no actual piece of plastic or metal rotating in there, a progressive system video camera samples images from the ccd's at a given frame rate. Frames per second and shutter angle are important because with a shutter angle (or in video terms shutter speed) of 1/250th you'll need to open up your iris. A simple way to think of this is Fps is the speed at which the film moves through the camera, shutter speed is how much light your giving your film or video. Is this confusing or helpful?
khmuse
Tech Guru
Kevin Briggs said:
As other have pointed out, in a motion picture film camera it is a moving system. There are two aspects of the camera which determine the exposure duration. One is the frame rate (typically 24 fps) and the other is the shutter angle. The shutter (or film gate) is a rotating device that has only a percentage of it open (the other part is reflective and is used to get an image to the eye piece and video tap).
The amount of time that the gate allows the image to be conveyed to the film is a function of the ratio of open versus closed and is expressed as an angle. If the gate were open 100% of the time (not possible) it would be expressed as a 360 degree shutter; therefore a 180 degree shutter would expose the film for 50% of the time. Multiple the equivalent time by the frame rate and you get exposure time:
Time = (shutter angle/360) * (1/frame rate)
an example might be:
Time = (180 degree shutter/360) * (1/24 fps) = (1/2) * (1/24) = 1/48
This example is identical to a shutter with a duration of 1/48 of a second.
In the case of a CCD imager, the shutter is electronic and directly controls the amount of time that the imager accepts photons (which displace electrons and produce a resultant charge).
The two are identical in function but are different based upon the fact that one is a mechanical system while the other is an electronic one.
John Godden
Well-known member
Oedipax said:
I'm a little confused on this point. i.e. fast shutter = jerky motion. Can you ellaborate a bit on this issue?
I always thought that the jerky movements in SPR were done with some 'special' post processing. FWIW, I hated that effect.................... didn't look at all like the original battlefield film I've seen.
THANKS
JohnG
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Barry_Green
Moderator
No post processing, they were done using a very abbreviated shutter angle (45 degrees I think?)
Hans Moleman
Carbonite Member
I find the best way to get realistic battlefield footage is to go to a special 'center,' and sign some papers. You'll get a pretty good look.
Anyway, it was a stylistic choice to convey a feel of detatchment, whereas battlefield footage is intended to capture the literal happenings. One's a portrayal, the other's a reporting.
John Godden
Well-known member
Barry_Green said:
Thanks for the info. Is there a simple explanation (or a web link) that would explain why an abbreviated shutter angle (or high electronic shutter speed) would generate that 'stuttered look'?
:dankk2: JohnG
Barry_Green
Moderator
Well, the narrower the shutter angle, the shorter the exposure time. The shorter the exposure time, the "crisper" the image -- less motion blur. Also, the shorter the exposure time, the longer the shutter is closed, which means that the subject can move farther without being imaged between shutter openings. The effect ends up being not unlike a strobelight.
John Godden
Well-known member
Barry_Green said:
Barry
Thanks for the additional clarification.
Interesting............... I found this after a short net search. An article on SPR and the filming process. One of the "tricks" used to accentuate the 'image strobing' was the following:
"........... Additional battleground realism was attained by attaching a Clairmont Camera Shaker to the cameras which forced the images to jostle and strobe as though the cameramen were truly dodging bullets."
Full article here: http://www.girlsaresmarter.com/laura/papers/SavingPrivateRyan.html
Regards
JohnG
Barry_Green said:
Ok, so if a too slow of shutter speed blurs motion, and a fast shutter speed records it too quickly (stacotto) then each frame rate must have an optimal shutter speed for normal cinematography?
Curious, what would those optimal numbers be for 60i, 30p, and 24p.
And, are there optimal numbers for each frame rate if you plan to slow the footage down to 50%?
Thanks,
Joe
Joshua Provost
Veteran
Joe,
The motion picture standard is a 180 degree shutter angle. So, half the frame rate. 24p = 1/48 shutter. 30p, 60i = 1/60 shutter.
If you want to do a 50% slow mo, cut the shutter time in half: 1/96 or 1/120.
Josh
The motion picture standard is a 180 degree shutter angle. So, half the frame rate. 24p = 1/48 shutter. 30p, 60i = 1/60 shutter.
If you want to do a 50% slow mo, cut the shutter time in half: 1/96 or 1/120.
Josh