We’ve all been in a situation where the perfect shot is right in front of you, but to get the shot involves getting into a strange position and holding your camera handheld. When you start shooting, you realize that no matter what you do, the footage you capture is always shaky. So what happens now? That’s where image stabilization (IS) comes in as it is designed to greatly reduce camera shake and vibration. There are two popular methods of image stabilization used by videographers – Electronic Image Stabilization (EIS) and Optical Image Stabilization (OIS). Read on to find out more on these two image stabilizers work, the differences between the two and the pros and cons of using either image stabilizer when shooting video. This is not a comprehensive guide to everything on the market, simply a brief educational guide to help you be a more informed consumer.
Electronic Image Stabilization
The Electronic Image Stabilization (EIS) system reduces image shake and controls image stability by manipulating the image electronically, using the light-sensing chip, the Charge Coupled Device (CCD) of the camera. Once the image hits the chip, and if the system detects what it thinks is camera shake through its sensors, it responds by slightly moving the image so that it remains in the same place on the CCD. For example, if the camera shakes to the left, then the image moves to the right to compensate, thus eliminating the shake. Basically, when the image zigs, the EIS system zags, by precisely the same amount.
There are two ways the EIS system works to reduce the movement of the image. The first method is to increase the size of the image by digitally “zooming in on the image so that it is larger than the CCD. By making the image larger, the system can then scan within the image to counter the movement created by the shake. To test if your camera utilizes this system, simply turn it on and watch the image through the viewfinder. If the image zooms in slightly, then it is using this method of image stabilization. However, because this system zooms in on the image, the image resolution is somewhat decreased.
The second method of the EIS system uses of an oversized CCD. As a video image covers only about 90 percent of the chip’s area, there is system space available for which to move the image. For example, when the image is stable, the chip centers the image on the CCD. But if the camera shakes to the right, there is space for the image to roam back to the left to compensate for the shake, keeping it in exactly the same place on the CCD, thus eliminating the shake.
Pros And Cons Of Using EIS
EIS systems are compact because they do not add any bulk to the lens, and fast because there is no need for any physical movement, as all the heavy lifting occurs electronically at ultra high speeds. On the down side, as the video image occupies only 90 percent of the CCD, when the image is electronically magnified to fill the remaining 10 percent of the frame, there will be an inevitable loss of image quality and resolution.
Optical Image Stabilization
The Optical Image Stabilization (OIS) system works a little differently than the EIS system, although the end result achieved is the same. The OIS system works before the image hits the Charge Coupled Device (CCD), meaning that no electronic adjustments are necessary and that the image is stable when it hits the chip, completely filling the chip’s entire surface area. This is done by placing a variable-angle prism near the front of the lens to bend the shifted image back center.
The prism is simply a pair of glass plates with a liquid-filled bellows system between them, where the bellows create the equivalent of a glass prism. As the image passes through the prism, the lens reduces or eliminates the image shake by detecting and matching the frequency and size or the amplitude of the shake and then rotating the plates of glass to change the angle of the prism. One glass plate rotates vertically, moving the image up and down. The other glass plate rotates horizontally, moving the image left and right. Similar to the EIS system, the idea is to move the image in the opposite direction from the shake, and if there is no movement detected, the prism mechanism simply centers itself.
Cameras with optical image stabilization typically also feature a gyro-sensor built into the camera to negate camera shake. The sensor measures any movement from the videographer and sends its measurements through a stabilization microchip to the CCD, which then shifts slightly to compensate for the movement. This type of correction is the most precise form of image stabilization, as it does not require increasing the ISO sensitivity, which can compromise the image quality.
Pros And Cons Of Using OIS
As OIS systems utilize the full chip area instead of CCDs, it is slightly heavier and bulkier than the EIS systems. Also, in theory at least, OIS systems do not respond as quickly as EIS systems because the prism mechanisms have to be physically moved. However, these drawbacks are hardly noticeable when actually using the camera.
Choosing An IS System
The type of image stabilization system you need greatly depends on the type of video you want to shoot. If your video requires the highest of image quality, then the Optical Image Stabilization (OIS) system will be your most ideal choice. If you require smaller, less bulky equipment and image quality is not a major concern, then you might want to consider the Electronic Image Stabilization (EIS) system. Whichever system you finally decide on, just remember that camera movement must be planned to be successful.
When it comes down to it, image stabilizers are not a must have feature, especially with the availability and convenience of a tripod. It is another tool that you can use to better capture your videos. But if you find yourself toying with the idea of getting a image stabilization system, then be sure to read this article to understand the specifics of the two most commonly used image stabilization systems before you step into your camera store.