Normally, the slowest shutter speed when recording movies is 1/30's second. Using the techinque I will inform about here, you can use as slow shutter speeds as 1/2 second.
The camera will only record at such shutter speeds with a number of features turned off. Follow this list:
- In the video recording menu, set the video recording mode to Motion JPEG, i.e., you can not use AVCHD.
- In the same submenu, define the Creative Movie Mode to give full manual control.
- Choose the Creative Movie Mode from the top mode dial, and select Manual Focus (MF). If you want, you can use autofocus when framing the subject, and go back to manual focus before starting to record the movie.
In the example below, the aperture is f/16, shutter speed is set 1/6's second, and the ISO is 100. After having done the steps above, you must set the exposure manually, by looking at the histogram. You can also adjust the ISO manually, if needed.
In the Creative Movie Mode, recording videos can be started and stopped by pressing the shutter key. Alternatively, you can also use the dedicated red movie button.
Here are three videos feature LEGO figures on a turntable, filmed at 1/2 second, 1/10 second and 1/60 second shutter speed. You'll notice that with a slower shutter speed, the number of frames is also smaller.
1/2 second exposure
Here is an example using the GH2 to capture fireworks at 1/4 second shutter speed.
Shutter speed and motion blur
As a general rule, you'll want to keep the shutter speed not too fast when filming. Professional movies are generally filmed at around 1/50-1/60 second shutter speed. The purpose of keeping the shutter speed fairly slow, is to give some blurring to moving objects. If the speed is significantly faster than this, movement looks strange, because there will be little motion blur. Any items moving will show up at different places in each frame, and with no motion blur, the human eye will be confused.
This is the reason why some video cameras have ND filters built in. In strong sunshine, it may be difficult to use a large aperture in combination with a shutter speed of 1/60 second. A Neutral Density (ND) filter will limit the amount of light passing through, without altering the aperture, hence allowing for a slow shutter speed. Using a smaller aperture is not always desirable, since it will give a wide depth of field, ruining the "cinematic" look.
The Panasonic GH1 does not have any built in function to provide ND filters between the lens mount and the sensor in strong light situations. If you want to use ND filters, they must be added to the front thread of the lens.
The upcoming professional Panasonic camcorder AG-AF100, to use the Micro Four Thirds mount, will feature built in ND filters.
When taking pictures, the Panasonic Lumix G series, as well as the Olympus PEN cameras, use a mechanical shutter. When you press the shutter release button, the shutter first closes, and then opens for the specified shutter speed, and then closes and opens again for continued live view.
When recording videos, the shutter stays open all the time, and the shutter speed implementation is done electronically.