Taking Good Video
Introduction
Video quality is critical in optimising the video sharing and analysis experience for you and your group.
This module will help you take better video and get more out of your analysis be it Technique Analysis (precise) or Gameplay Analysis
(whole body movements).
The main topics covered in this module are:
Lighting
Shutter speed
Frame rate
Focus
You can find a comprehensive
supplementary PDF resource
document by clicking this image.
The Setup for Technique Analysis
The Setup for Gameplay Analysis.
Calibration object
Other tips
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Taking Good Video
Lighting
Lighting is first on the list and for good reason. Lighting is one of the most important variables influencing video quality.
Outside daylight is often a better option but capturing video inside can be a problem. For example in a gym, hall or fitness center.
The image sensor in the camera needs a certain amount of light reaching it to create a bright image. However, in low light this means the shutter must
stay open for longer which in turn means any movement occurring while the shutter is open will result in a blur.
In some cameras if the image is blurred you can sometimes set a faster shutter but that will result in a darker image so you will need more light.
Generally with most modern cameras if you have blurring in your video image you need more light.
In the following baseball images focus on the fast moving bat and ball.
A good bright image (due to fast
This image is sharp (so the shutter
The image is bright but the fast-
shutter and lots of light) with well
is fast) but very dark because there
moving bat and ball are blurred due
defined edges taken from a video.
is not enough light to brighten it.
to a slow shutter as the camera
attempts to get a brighter image.
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Taking Good Video
Shutter Speed
A fast shutter gives you a sharper image, however a fast shutter does not give the camera's sensor much time to get enough light to create a bright
image. Therefore you need lots of light (see previous page).
A slow shutter gives the sensor more time to collect light to create a bright image but if there is movement while the shutter is open, blurring will occur.
Most cameras, especially cheaper ones, do not have a manual shutter. In these cases to get a sharper image make sure you have a lot of light as most
devices will increase their shutter speed if they detect good lighting conditions.
In the following baseball images focus on the fast moving bat and ball.
A fast shutter to give a sharp image but
With a slow shutter the bat and ball
A fast shutter in good light gives a sharp
there is not enough light to create
moves while the shutter is open and
image.
a bright image.
blurring occurs.
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Taking Good Video
Frame Rate
The frame rate is the number of images the camera takes per second, or frames per second (fps).
General consumer cameras do not offer the user any frame rates apart from the usual 25/30 or 50/60 fps.
Refer to the 'Types of Cameras' module for information on cameras that offer higher frame rates.
100 frames per second
25 frames per second
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Taking Good Video
Focus
Many cameras have a manual and an auto focus.
Auto focus generally works well however there are instances
when it does not.
For example if the camera is focused on a far wall then the person
of interest walks close to the camera there is a rapid and dramatic
change in focal length.
In this case you should manually focus on the person as they stand
in front of the camera.
An example of a video captured on a camera out of focus.
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Taking Good Video
The Setup for Technique Analysis
Technique analysis is looking at the biomechanics of the skill. For example the position of one body
part relative to another, joint angles, speeds etc.
To do this effectively the camera must be set up correctly.
This means the camera must be:
On a solid mount, a tripod at half the height of the action of interest is best.
Well focused and the action should fill the entire field of view.
Level, horizontal and perpendicular to the line of motion of the person of interest.
The space must be uncluttered and a neutral background is optimal.
If you want to measure distance or speed you need to have a calibration object in view (for
more details see page 9)
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Taking Good Video
The Setup for Gameplay Analysis
In Gameplay analysis the observer is usually interested in whole body movements around a court or field.
For example how long does it take for support to arrive at a breakdown in play, what are a players options at this point (image below), how
long did a team spend on the oppositions half, what is their defensive formation etc.
In these cases observer is not taking measurements directly
off the video itself but watching the video and recording key
event like those mentioned above.
In this regard the position of the camera is not as critical as
technique analysis.
What is critical is that the camera's field of view covers the
action and is well focused (auto-focus usually works well
here).
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Taking Good Video
Calibration Object
If you want to take distance and speed measurements off the screen using the Analysis tool in Siliconcoach Live you need to have something in the
image of a known distance.
In the software you will be asked to click on each end of this object and enter the real world distance between the ends. Now the software can calculate
the real world distances of other objects on the screen.
There are some restrictions.
The object you use for calibration must be in the same plane as the motion of your person. For example you cannot have the 3m calibration
marks on the walls of the basketball gym while filming the shooter at the free throw line. Generally the calibration object should be under the
throwers feet.
If you change the video you must re-calibrate.
An example of a calibration
process.
The user enters the real-world
distance (e.g. between marks on the
floor) into the software and it
calibrates the screen for further
distance and speed measurements.
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Taking Good Video
Other Tips
Demo mode
Some camcorders come with a Demo mode that turns on after about 10 minutes and does all sorts of crazy things to the image on the cameras
screen.
It adds shake, makes the image sepia, black and white, grey scale etc. You need to turn this off.
Clothing
For Technique Analysis the subject should wear as little clothing as practical and whatever clothes they have on should be tight fitting. The clothing
should also contrast with the background and allow the analyst to see the shape and position of the body segments.
For Gamneplay analysis you usually will not have much say in the clothing as it will be a competition situation, but as long as there is some contrast
between the players and the background, clothing is usually not an issue.
Sun
Try to avoid pointing the camera toward the sun, if you do your subject(s) will appear very dark.
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Taking Good Video
Summary
To capture good video you must:
Identify if you are doing Technique Analysis (precise) or Gameplay analysis (whole
body movements).
Have very good lighting as this gives you a brighter and sharper image.
A high shutter speed is important but you need more light for this.
A frame rate that is high enough to capture the key events in the action.
Make sure you focus the camera.
Avoid pointing the camera toward the sun
For Technique Analysis have the camera mounted on something steady, it is level,
horizontal and at half the height of the object of interest. Also if you are going to
take measurements of the screen you must have something a known length in the
frame.
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