Image Stabilization Explained
The right focus and good lighting is needed to create sharp and clear images. The correct way to capture that would be to have a steady hand and proper eye coordination. Traditional photographers have developed their own techniques for a steady way to shoot handheld. By taking a firm grip of the camera and slowly releasing the shutter button, they can minimize any shake that can affect the focus and clarity of the image. This was a time before digital cameras, so it was a skill that became very much in demand. That was the definition of a photographer, someone who can take clear, sharp and well composed images. So what is the trick behind it? It is about image stabilization.
Stability Is Key To Great Images
If you wonder why your images appear blurry, jittery and out of focus, it is because it was shot with too much shake. The hand must be more steady in order to properly set the focus and capture the image. This becomes noticeable after taking many photos with a camera. Some will appear clear and sharp, while others are soft and blurry. When taking a shot with the camera, it is important to make sure that any hand shake or movement is minimized, as much as possible. The slightest movement can cause the focus to change and thus affect the image quality.
Stabilizing an image is important in order to get the best quality in an image. That would also require stabilizing the camera. Photographers needed a way to help them capture images. Apparently, steady hands alone don’t always capture the best images. Eventually holding the camera can be tiring. Even the best photographers will need help in the form of a tool or device to stabilize the camera. A stable camera helps to capture the image with the best quality since stabilizing the camera reduces if not prevents shake and blur.
Avoid The “Shake”
Changing the shutter speed is another way to help reduce the effects of handshake blur or camera shake and movement. The faster the shutter speed, the better capturing a sharper image. With slow shutter speed, the least hand movement is required otherwise the image quality will suffer. Even though faster shutter speed captures sharper images, it is better to shoot slow shutter speed in low light conditions. Faster shutter speed does not allow enough light from the aperture to the sensor to get a better lit image. There are various guides out there to help beginning photographers take better shots by improving their stance and properly holding the camera. This is why it is really night and day when you compare the work of a professional photographer with a novice. With today’s cameras, there are new technology that help even the least experienced photographer to stabilize their camera and capture better images.
Better For Low Light
For night photographers or low light photography, image stabilization helps considerably. It allows photographers to use a shutter speed that is 2 to 4.5 stops slower to capture sharp and detailed images despite having less light. This works because slow shutter speeds can capture more available or ambient light passing to the aperture. The slow shutter allows the image to be created by allowing more light to collect on the sensor, thus bringing out the highlights from the contrast. Slow shutter speeds handheld, can still be blurry and jittery due to hand movement. It is best used with a stand or tripod, for slow shutter speeds to work. Slow shutter speeds when used with image stabilization allow photographers to get creative with shooting in low light.
“Rule of Thumb”
Before I discuss the different types of image stabilization, I will discuss the Rule of Thumb. This is a principle to follow when shooting handheld that allows for no noticeable blur in the image. According to this rule, you take the reciprocal of the focal length of the lens also called the “1/mm Reciprocal Rule”.
Here is a quick example:
Let us say your lens has a focal length of 400 mm.
Shutter Speed = 1 / 400 of a second
This means if you have a shutter speed slower than 1/400 of a second, camera shake would affect the sharpness of the image. With image stabilization, it allows the photographer to shoot at 2 stops slower than 1/400 of a second.
You also have to take the crop factor multiplier into consideration depending on the size of the sensor. If the crop factor of the sensor is 1.5 (Nikon DX), then multiply that with 400 mm.
Effective Focal Length = 400 mm x 1.5 = 600 mm
The effective focal length becomes 600 mm. Thus the reciprocal now becomes:
Shutter Speed = 1 / 600 of a second
With image stabilization you can bring it down by 2 or 4.5 stops slower. Now following the rule, 1/600 of a second does not have a direct equivalent with the shutter speed scale:
1/2000s, 1/1000s, 1/500s, 1/250s, 1/125s, 1/60s, 1/30s
However, we can approximate it to 1/1000 of a second. At 2 stops down from 1/1000 of a second (when approximated) it is 1/250 of a second. At this shutter speed with image stabilization, you can still shoot handheld without much noticeable blur. Then again it really depends on how steady your hand is because there is really no way to perfectly correct immense camera shake. This is just an example, so if you take other factors (e.g. aperture, sensor type) into consideration you will come up with different calculations.
Types Of Image Stabilization
Cameras today, including smartphones, use different types of image stabilization to capture sharper images. They can use physical, optical or electronic (even a combination) image stabilization techniques.
Physical — These are devices or tools used with the camera to help stabilize it to capture images. A common device traditional photographers used in order to stabilize their camera was the tripod. It contains a mount for the camera and leg stands to support it. The tripod prevents shake and reduces blurriness. Other tools that help photographers stabilize the camera include gimbals, monopods, steadicams, arm mount, studio stands , camera strap (yes, the one on the camera you put around your neck) and braces (among the many types). This is the most common way to stabilize the camera and also the more traditional technique used prior to the popularity of digital cameras. Big production studios who work on cinematic film use these devices overwhelmingly. Creatives who produce content on sites like YouTube and Vimeo also use them. The selfie-stick is an example of a camera stabilizing device popular with smartphone users. Remote shutter release on a camera, either wirelessly or by cable wire, also helps to physically stabilize it. This usually requires using a tripod as well for mounting the camera on.
Optical — When you cannot or do not want to use a tripod, there are other techniques that are built into the camera or lens that provide image stabilization. Optical Image Stabilization (OIS) uses a hardware based mechanism that controls the image coming through the lens to align with the sensor. The lens moves in the opposite direction of the camera shake. This involves the use of gyroscopic sensors that will sense camera shake when the image is not aligned with the sensor. If the image is not aligned with the sensor, it will not be captured sharp and in focus. This type of technique is used by major camera makers (e.g. Canon, Nikon, etc.) that implement it on the camera’s lens. Nikon calls their technology VR (Vibration Reduction) while Canon simply calls their technology IS (Image Stabilization). DSLR and medium format cameras can have heavy lenses attached to them, making it difficult to capture steady images handheld without the use of a tripod. There is a counterpart to OIS called In-Body Image Stabilization (IBIS), which implements the image stabilization feature not on the lens, but within the camera’s body. IBIS is common on mirrorless cameras while OIS on DSLR cameras.
Electronic — It is also possible to stabilize the image using software based mechanisms called Electronic Image Stabilization (EIS) aka Digital Image Stabilization (DIS). This uses the techniques of computational photography, which allows correcting the image using algorithms programmed into the camera’s firmware. To reduce the effects of unsteady hands, the EIS uses sensor-shifting algorithms in software to correct the image alignment. The software will reduce any blur or compensate for camera shake using complex algorithms that shift the pixels in the image. EIS has become common with some smartphone cameras. They are regarded as intelligent devices because the EIS can work alongside AI software to produce even better results. An example of the amazing results from EIS can be demonstrated by the Google Pixel smartphone camera.
Some Known Issues With Stabilization
There are some issues to image stabilization which are inconsequential results of the reality of physics. It is good to be aware in order to understand what could happen so as to avoid them.
Falling Cameras On Tripod — When using a tripod (or any camera stand), cameras could tip over and fall. That could be a very expensive mess to deal with if the camera is broken as a result. This is because the camera could tilt the tripod or stand when its weight is too much (e.g. with large lenses attached, this can happen). Cameras tipping over on tripods happen more often outdoors, during on location shoots. In windy places this will most likely happen if the camera is left alone. In that case, the photographer should remove the camera from the tripod. Accidents are also a reason cameras fall from tripods. Either it was unintentionally knocked over by a passerby or the camera was not properly attached to the tripod or stand. Steadicams or a more stable type of tripod would be ideal when shooting on location.
Camera Shake From VR — It is important to note that the VR (aka IS for Canon shooters) must be disabled on the camera’s lens when mounted on the tripod. Though the VR reduces vibration, when mounted on the tripod, it could actually cause it. This is because VR sensors will try to correct the image when vibrations are detected. When mounted on the tripod, the VR could detect no vibrations and negatively interpret this. When there is no vibration to detect, even a slight one, the VR system could still shift thus causing the unwanted effects of what it is supposed to do. The reason this happens is because the VR system was designed to always respond to vibrations when the shutter is released. That means if there is no vibration detected to correct, the lens will still move but this time it creates a blur because it doesn’t align the image to the sensor. There are others though, who refute the recommendation of disabling VR. This is because if you have a big focal length lens mounted on the tripod, the shutter release vibration could cause the lens to vibrate. It could lead to a sharper image with correction from the VR system on the lens. Some camera lenses and body today have a tripod detection sensor that disables the image stabilization automatically. Otherwise, the photographer does not need to disable it at all.
Cropped Images From EIS — The EIS technique usually results in either a smaller cropped image or an extrapolation technique that fills in the lost edges. This is because when the pixels are shifted, the pixels need to be adjusted to capture the image correctly. This means it will not be possible to capture the frame the way the photographer wants, because the EIS will crop the image. For example, let us say that the composition a photographer wants must include a scene that fully captures a subject from waist up. Shooting handheld, the photographer generates plenty of camera shake so the EIS attempts to correct this. In doing so, the image’s pixels are adjusted to a correct alignment with the sensor. This results in a different crop of the image in which the algorithm calculates the sharp pixels and disregards the bad ones. Often times this is not an issue unless it must be specifically shot without any cropping.
OIS Is Slow — Since OIS uses mechanical parts (e.g. lens), it can be slightly slower. This affects shooting fast motion and action shots. It could mean losing a nice frame that could have been the best during a burst of shots. This may not be much of an issue since OIS has been in use by professional sports and action photographers for a long time. However, newer camera systems that use EIS with dual-pixel technology can be faster. This is because they don’t need to move the lens to align the image. All that is done digitally (software) and electronically (sensors) by the camera. This results in capturing more interesting shots in the frame and thus ideal for video and slow motion sequences. Primarily it has been observed that OIS is great for photos while EIS is best for videos.
It is nice to have image stabilization when shooting handheld or in low light conditions. For cameras with large lenses, the results are very significant. Without using any form of stabilization on the camera, the photographer is required to have a good stance and steady hands. Those were skills developed by film photographers since they lacked the image stabilization used today. Intentional camera shake and blur can actually be done for artistic purposes. This still requires some skill, since the effect it creates if meant for art’s sake should have some aesthetic appeal.
Now there are more types of features that incorporate image stabilization in cameras, allowing for the creation of clearer and sharper images. It makes it easier for non-professional or anyone who wants to take their best photos. With the popularity of photo sharing on the web and social media, taking excellent photos becomes important to users. The benefits this brings adds value to the camera, whether it is on a smartphone or a full-frame DSLR. That makes image stabilization a very useful feature for all types of photographers.