Movie camera speed

[MistaPi]

A bit offtopic, but does a movie camera always run at 24FPS speed. What about differens in a bright outdoor scene and in a dark indoor scene. Would they not have to adjust the shutter speed accordingly to the light intensity to avoid over exposure or to little exposure?

 

[pcchen]

The shutter speed is independent of frame rate. You can see it as someone shooting pictures at 24 frames per second. Each frame may have different shutter speed depending on the light condition.

In good light condition, shutter speed is generally much faster than the required 1/24 second, so that can introduce temporal aliasing (such as when filming a fast rotating wheel).

 

[MistaPi]

What does that mean exactly. Does the same frame get exposed serveral times then?

 

[Simon F]

A bit offtopic, but does a movie camera always run at 24FPS speed. What about differens in a bright outdoor scene and in a dark indoor scene. Would they not have to adjust the shutter speed accordingly to the light intensity to avoid over exposure or to little exposure?

To my knowledge, traditional movie cameras expose each frame with a maximum 1/48th of a second shutter speed (though this could be shortened for "jerky vision" cinematic effects.). The remaining time is used to physically advance the film.

If you have bright lighting you don't want to shorten that time because of temporal aliasing - wagon wheels are bad enough already! Instead just use a smaller aperture or a neutral filter.

For indoor work I believe they just use rather bright lights

 

[MistaPi]

Thanks for the replies.

Another question. When fast moving objects get blured out in real life, is it because the eyes can't focus fast enough or is it because the brain can't process the information fast enough?
Is there a good article about this?

 

[Mintmaster]

Would they not have to adjust the shutter speed accordingly to the light intensity to avoid over exposure or to little exposure?

Don't forget about lens aperature and the use of filters, either. Light can be reduced in many ways, not just shutter speed.

 

[pcchen]

Thanks for the replies.

Another question. When fast moving objects get blured out in real life, is it because the eyes can't focus fast enough or is it because the brain can't process the information fast enough?
Is there a good article about this?

To my understanding, there is no "shutter" in human eyes. At least, not the mechanical ones The sensor cone/rods in human eyes also don't behave like CCD or CMOS sensors in digital cameras. Each pixel in these sensors accumulate electrons converted from photons, then the amounts of electrons are read out to form the image. So you can have "electrical shutters" in these sensors. However, in human eyes, electrons are not accumulated in the sensors, but sent through a neural pulse to the brain. Therefore, in a sense, it's the brain which acts as the accumulator. So you can say the blurred image is produced by brain's (temporal) low pass filter.

 

[FrameBuffer]

To my understanding, there is no "shutter" in human eyes. At least, not the mechanical ones The sensor cone/rods in human eyes also don't behave like CCD or CMOS sensors in digital cameras. Each pixel in these sensors accumulate electrons converted from photons, then the amounts of electrons are read out to form the image. So you can have "electrical shutters" in these sensors. However, in human eyes, electrons are not accumulated in the sensors, but sent through a neural pulse to the brain. Therefore, in a sense, it's the brain which acts as the accumulator. So you can say the blurred image is produced by brain's (temporal) low pass filter.

iirc it's called persistence of vision (reportedly discoverd by Ptolemy), theory states that the eye takes a fraction of a second to "record" an impression of an image and send it to the brain, once recieved, the eye retains it for about 1/10th second. Films are not a continuous stream of images in succession, each image is held within the gate (a slight pause) then the shutter closes and the next image is presented.. again and again.. otherwise all we would see is a constant blurred image.

 

[pcchen]

iirc it's called persistence of vision (reportedly discoverd by Ptolemy), theory states that the eye takes a fraction of a second to "record" an impression of an image and send it to the brain, once recieved, the eye retains it for about 1/10th second. Films are not a continuous stream of images in succession, each image is held within the gate (a slight pause) then the shutter closes and the next image is presented.. again and again.. otherwise all we would see is a constant blurred image.

My point is that the brain does not see individual images, unlike a film camera.