Measuring distance from camera to subject
- Thread starter Lor
- Start date
renegadewill
Well-known member
just pull focus, same thing
Andrew Brinkhaus
Veteran
basically,
Pulling tape to measure the distance to a subject from the film plane or camera sensor delivers the exact point which is in focus at a certain f-stop, distance, and focal length. Those three elements are the determining factors of DOF.
When that distance is measured, it could then be calculated how far in front, and how far behind that focus mark is also within acceptable focus. This gap determines how far the subject can move forward and backward and still be sharp. This level of sharpness is determined by the CoC of the setup, because projected, images of different sizes will appear at different sharpness levels. The distance in focus in front and back can be calculated with a Kelly Wheel or depth of field calculator.
For more on DOF and the way it works, check this out.
http://www.dvxuser.com/V6/showthread.php?t=893
Pulling tape to measure the distance to a subject from the film plane or camera sensor delivers the exact point which is in focus at a certain f-stop, distance, and focal length. Those three elements are the determining factors of DOF.
When that distance is measured, it could then be calculated how far in front, and how far behind that focus mark is also within acceptable focus. This gap determines how far the subject can move forward and backward and still be sharp. This level of sharpness is determined by the CoC of the setup, because projected, images of different sizes will appear at different sharpness levels. The distance in focus in front and back can be calculated with a Kelly Wheel or depth of field calculator.
For more on DOF and the way it works, check this out.
http://www.dvxuser.com/V6/showthread.php?t=893
Back when film was more prominent, DPs mostly (99% of the time) shoot with Prime lens only. On prime lenses you cannot zoom in to focus and zoom out. Even if you can, you still have to set the eye piece to your eyes. Therefore, it is a lot more accurate to measure the distance. An AC can do the measuring while the DP is discussing the shot with the director and gaffer. More than likely DPs will already have a good idea of a certain depth of field already, because of the f-stop and lens that they are using.
The answer to your question is, they measure to get an accurate focus, because the depth of field is so small in most of the lens that they shoot in.
Nowadays with video cameras, you can just zoom in to check your focus and your good to go, even on high end 2/3" camcorders.
Kak Lee
www.myspace.com/kaklee
www.hmoobfilm.com
The answer to your question is, they measure to get an accurate focus, because the depth of field is so small in most of the lens that they shoot in.
Nowadays with video cameras, you can just zoom in to check your focus and your good to go, even on high end 2/3" camcorders.
Kak Lee
www.myspace.com/kaklee
www.hmoobfilm.com
Postmaster
Dark Side of the Camera
...as long the actor stops on his marks and moves not too fast fro and back.
Frank
Frank
Charles Lowthian
Well-known member
Nowadays depth of field is less transfered
but that's why we can put adapters onto video cameras to maintain the depth of field :2vrolijk_08: shallow focus