Camera without optical stabilization. How does optical stabilizer work?

Percentage of sharp images depending on shutter speed

Introduction

I use equipment from Canon and Nikon. Their stabilizers are called IS and VR. IS (Image Stabilization) is an abbreviation of Canon, VR (Vibration Reduction) is Nikon. The image stabilizer helps me get much clearer images with long lenses and also in low light conditions.

IS and VR are so important to getting great photos that I won't buy a lens without them if given the choice.

VR vs IS

VR (Nikon) and IS (Canon) are the same thing. I will use both terms interchangeably. Each manufacturer uses their own abbreviations.

Both of these systems stabilize the image to avoid blur from hand shake. This helps in many cases to do without a tripod and get sharp photos. VR and IS allow me to shoot in low light without using a tripod, except when it's really dark (twilight or night).

VR and IS work great when shooting still subjects, which is what I shoot most of the time. Of course, stabilization systems are useless for shooting moving objects, sports or children.

Some people like to use VR and IS for tracking shots, in which case the stabilizer works in one direction while in others the shot comes out blurry.

To get a sharp shot of a fast-moving subject, you will still have to use either a faster lens, more light, or raise the ISO.

The stabilizer only helps compensate for camera shake, but cannot do anything with moving objects.

Other manufacturers

Minolta, Panasonic, Olympus and Sony

Minolta (now Sony) makes DSLR cameras that already have image stabilization built into the camera. I haven't tried these systems. Their advantage, according to the manufacturer, is that they work with any lenses, since the stabilizer is located in the camera and not in the lens.

Anti-Shake

Beware of such names. Most manufacturers who use this term are deceiving the consumer and simply increase the ISO to get a faster shutter speed. You can increase the ISO yourself. Typically these cameras do not compensate for hand shake like VR and IS systems do.

How do stabilizers work?

I'll skip the details, the basic principle is that motion sensors predict motion direction and speed in the initial phase when the photographer presses the shutter button and takes the photo.

They then use various lens or array shifters out of phase with the detected error signal to counteract this movement.

Due to this, the image is stabilized during exposure.

You can see the stabilizer in action through the viewfinder of SLR cameras or on the screen of compact cameras by pressing the shutter button halfway.

Schedule and reality

Hand shaking, which doctors call tremor, is random.

Take enough photos in any conditions. Some will be sharper, some more blurry. The percentage of hits depends on conditions, shutter speed, and focal length.

The graph shows how the percentage of your shots that are sharp depends on the shutter speed. At very long shutter speeds, for example 30 seconds, you will almost never get a sharp shot, regardless of the presence of a stabilizer. But the probability of this is not zero, since there is a lucky chance.

At fast shutter speeds like 1/1000, you'll get sharp photos almost 100% of the time, again regardless of whether you have a stabilizer or not. But almost 100% is not pure 100%. There are exceptions to the rules.

It all comes down to the methods of probability theory and statistical analysis. Mathematicians will be able to explain this better.

The old wives' tale about shutter speeds being no longer than 1/30 or 1/(focal length) comes from the observation that most people get about 50% of their shots sharp under these conditions. This exactly corresponds to the middle section of the black curve on the graph. Being a random function, a faster shutter speed will produce a higher percentage of sharp shots, and vice versa.

Trick

Since photography is a game, I try to increase my chances of success by shooting continuously. I increase the shutter speed and take several shots in a row in this mode. Later I choose the sharpest ones. The longer the shutter speed, the longer the series you need to make. To get at least one sharp shot. For example, if the probability of getting a sharp shot is 10%, then I take 10 or 20 shots in a series and choose the best one. It works!

In the same way, we can get a blurry shot with a normal lens at a shutter speed of 1/250 second. But this should not happen often, otherwise learn how to use the camera.

The stabilizer in this case always increases the chances of success. I don't know of cases where this was not the case.

When is a stabilizer effective?

VR and IS provide a significant improvement where the graph curves separate. Try shooting at a shutter speed of about 1/2 - 1/15 with a normal lens and you will see the difference between night and day. With shorter shutter speeds, the pictures will be sharp, but with longer shutter speeds, the stabilizer will no longer help.

Examples

Image of the room where the shots were taken

I took pictures with a Nikon D200 camera with an 18-135 lens without stabilizer and a Nikon D70 camera with an 18-200 mm VR lens. I'll show the photo from the D70 at 100% scale, and the photo from the D200 a little smaller so that they match.

Hover over to see the difference

Now do you understand why I think that it is better to buy the camera itself (the body) cheaper, and buy the lens more expensive? Remember that lenses can last for many years, but bodies change almost every year. The cheaper D70 with the 18-200 lens and VR shoots much better at longer shutter speeds than the much more expensive D200 without the VR lens.

Of course, they were compared at a focal length of 28mm and a shutter speed of 1/4 second, where the stabilizer makes a big difference. At shorter shutter speeds the difference will not be as significant, but it will appear at longer focal lengths, even on a sunny day.

Hover over the image to compare a shot taken with the D200 without a VR lens and a Canon SD700 compact with IS.

Image stabilization is key to getting sharp photos in typical indoor lighting conditions. Even a small pocket camera with a stabilizer can easily beat a DSLR if you use a lens without a stabilizer, provided you are shooting in low light without a tripod.

For each of the pictures I took six pictures. With the stabilizer, five or six were sharp. Without stabilizer, five or six turned out blurry. I took quite a lot of pictures so that the sample could be called representative.

Sorry that the size of the pictures and the exposure do not completely match, since I shot with different types of cameras. Oddly enough, pictures from a pocket camera look sharper, apparently due to the fact that in-camera processing uses more sharpening compared to a DSLR.

Tripods

I usually turn off the stabilizer on a tripod, since it is not needed. But even if I forget, I don’t see a problem with it.

Many stabilization systems are smart enough to detect that the camera is on a tripod and turn off. But if you're shooting in strong winds or your tripod isn't very stable, a stabilizer will also help.

Long exposure photography

If you shoot handheld with a long shutter speed, on the order of several seconds, a stabilizer will usually improve the result somewhat.

Frequency ranges

Vibration has amplitude and frequency. Stabilization systems are capable of processing vibrations only in a certain frequency band.

The range of interest to us lies in the range from 0.3 Hz to 30 Hz.

VR and IS ignore very low frequencies, as they would otherwise cause difficulties in tracking or tracking shots.

Frequencies above 30 Hz are also not particularly important. Our muscles do not contract faster than 30 times per second, and external high-frequency vibrations are filtered by our body mass and the mass of the camera.

Never place the camera on anything that vibrates at a high frequency. Hold it in your hands so that the vibrations are absorbed by your body.

Above a certain range of amplitude (vibration strength), the mechanics of the stability control system can no longer compensate to counteract a large displacement, for example, if you are removing from a car that is driving off-road.

Active or normal mode (Nikon)

If you have a switch for these parameters on your lens, it optimizes the system for different frequencies and amplitudes

Active mode is suitable for large displacement amplitudes, which are ignored in normal mode, assuming that you are doing the wiring.

I've never seen any difference in their performance, I usually shoot in normal mode. I figure that if I'm filming something moving, the VR system won't cope one way or another. Sometimes I use active mode, but not often.

Airplane

Stabilization systems are designed to compensate for hand tremors, not shooting from moving cars or helicopters. These are much stronger vibrations that require external stabilizers such as gyroscopes.

When filming from an airplane, never rest the camera on a door or any other part of the airplane. Instead, hold the camera in your hands and sit up straight with your shoulders away from the seat, so your body absorbs as much vibration as possible.

As always, you have to proceed by trial and error. When I was shooting from the open windows of a small plane, Nikon's VR system couldn't handle it, which makes sense since it's not designed for that.

Very fast shutter speed

VR and IS work very well at fast shutter speeds too, especially with long lenses where you can feel the difference.

Thanks to modern digital technology, we can immediately evaluate the result, which was impossible when shooting on film. If the image is even slightly blurry, it can be easily seen on the camera screen.

So even shots at 1/1000th of a second with 300mm lenses can improve when using a stabilizer. I use it all the time.

Although the stabilization system does not respond to high vibration frequencies, these vibrations were never an issue for short shutter speeds.

The problem when shooting with a short shutter speed is the same - vibration with a frequency of 0.3 Hz - 30 Hz. A fast shutter speed reduces the effect of vibration, so VR is not as effective at fast shutter speeds, however, with long lenses that are very sensitive to vibration, VR and IS are quite useful.

With short focal length lenses at fast shutter speeds vibration is generally not an issue, however a stabilizer can improve things here as much as possible.

Although high frequency vibrations are not a problem, they can produce subharmonics falling in the 0.3 Hz - 30 Hz range, which are amplified by long lenses. The stabilization system effectively copes with just such vibrations.

Failures

VR and IS systems can sometimes fail and operate with errors. If this happens, turn them off until you can return the lens for repair.

My first Canon 28-135mm IS had an interesting stabilizer defect. It worked well at long shutter speeds, but in daylight and at short shutter speeds the pictures turned out worse!

I sent it to Canon under warranty and Canon quickly replaced the system, resulting in the lens working flawlessly.

This is why I always test newly purchased lenses. I shoot with and without stabilization, at different shutter speeds and focal lengths, to see where I get the best results. This way you can even catch a rare manufacturing defect.

Using IS and VR makes a big difference in getting sharp images down to about 1/60th of a second with normal lenses and up to about 1/500th of a second with telephoto lenses.

Shutter speeds longer than a few seconds reduce the stabilization's effectiveness, but it's still better than nothing if you don't have a tripod or can't stand the camera on something solid.

The stabilizer can help even at very fast shutter speeds with long lenses

My best photos are taken outdoors at dusk. That's why I love VR and IS

I always keep the stabilization system turned on, except when the device is on a very strong tripod. I also use a stabilizer when shooting with monopods.

It is believed that in order not to blur the frame when photographing handheld, you need equal: 1/focal length.

At the same time, 1/focal length is a limiting value and does not guarantee a sharp frame. Therefore, you need to take a series of frames before a normal result comes out; the stabilizer shifts this limit by 4 stops but does not eliminate the need to take a series of frames. For those who don’t understand, I’ll try to explain with an example.

Example. You walk around the city with a DSLR camera and a photographic mood, you see something interesting, stop, take a photo, look at the screen - the frame is blurry. Don’t panic, look at the focal length - 200mm, which means that in order to photograph a clear frame hand-held, you need 1/200 sec (one two-hundredth of a second), take one or two or three frames and get the desired result. So, if without a stabilizer you take pictures at 1/200 sec, then with it you can take pictures at the same focal length (200mm) but at 1/60 sec!

Let's assume that you have a camera with a stabilizer. Otherwise, you will be interested in reading this article only out of curiosity. Today, stabilizers can be found both in expensive professional SLR cameras and in point-and-shoot cameras, and this is no longer some kind of exotic thing, but a functionality that is shoved where it is needed and not needed.

Conventionally, all manufacturers of SLR cameras can be divided into two groups: the first decided to install a stabilizer into a SLR camera onto a matrix(Pentax, Olympus, Sony), and the second into the lens(Canon, Nikon). I can't say for sure which is better. The first option is more versatile and cheaper, while the second is reliable and of high quality.

All manufacturers designate the stabilizer differently, Nikon - VR(Vibration Reduction), Canon – IS(Image Stabilization), Tamron – V.C.(Vibration Compensation), so don’t worry about what the manufacturer calls it, they work the same for everyone.

Do I need a stabilizer? A stabilizer is generally a useful thing, and in some cases it is simply irreplaceable. I'm talking about telephoto lenses, it is with these lenses that you will feel all the advantages of the stabilizer, otherwise you will be able to take photographs either on a bright day or with a tripod, as my father and grandfather once did. To understand the importance of a stabilizer in televisions, I advise you to read reviews of some of them (,). If you have a wide-angle or portrait lens, a stabilizer is not needed at all.

How and when to use it? Everything is very simple, regardless of the manufacturer, they all work the same.

And further. The stabilizer needs to be turned off when you take photographs with a tripod or by placing the camera on a surface, precisely because of the random nature of its mechanism. 95% of the time it behaves correctly, but it’s the last 5% that can ruin your shot.

Remember, a stabilizer can only help you when shooting static objects; when photographing dynamic objects (moving), it will not help you in any way, so don’t even count on it. A stabilizer is not a panacea, and in poor lighting conditions you need to take a series of shots.

Let's sum it up

A stabilizer is a necessary thing, but not mandatory, except in cases with telephoto lenses. Often it saves 3-4 stops of shutter speed, but does not eliminate the need to take several shots, all due to the random nature of its mechanism. It will not save you when shooting moving objects.

Karpukhin I. V.

The article explores methods of image stabilization. The main technical characteristics, as well as the advantages and disadvantages of different methods are considered.

Keywords: image stabilization, optical stabilizer, digital stabilizer.

Introduction

Modern requirements for optical devices come down mainly to a combination of two contradictory characteristics: high angular resolution and minimal weight and overall dimensions of the device. These requirements also apply to equipment operating on a moving or insufficiently stable base. To preserve the potential capabilities of optical devices in the field of resolution, various additional mechanical devices are most often used to reduce the influence of base movement on image quality. Such devices are called image stabilization systems.

1 Image stabilization methods

There are two main methods of image stabilization: optical and digital (electronic). Electronic image stabilization uses a comprehensive software algorithm to improve image quality. Optical is a hardware solution.

1.1 Optical image stabilization

Optical stabilizer consists of two elements: a motion detector - a system of gyroscopes that record the movement of the device in space, and a compensating lens. The principle of operation is as follows: the compensating lens in the lens is shifted in the opposite direction from the displacement registered by the sensor. As a result, light rays in all frames fall into the same area on the light-sensitive matrix. Taking readings from the detector occurs more often than reading data from the matrix, and the lens has time to correct its position even before taking the image from the matrix. Thanks to this, there are no image shifts between frames or blur within one frame.

One of the disadvantages of an optical stabilizer is the use of expensive and complex mechanical elements in its production. In addition, the presence of an optical group of several elements can affect the lens aperture, that is, the ability to provide a particular level of image illumination for a given object brightness.

In general, optical stabilizers are divided into two types: the first move the entire device on a movable base, the second move the optical elements inside the device. In the latter, the following elements are usually used to stabilize the optical image.

Mirrors. To change the direction of the sighting beam, a plane-parallel mirror with an internal or external reflective coating can be used. To rotate the line of sight to a given angle, the mirror is rotated by half an angle.

Wedges. For small deflection of the sighting beam with significant mechanical movement, refractive optical wedges are used. Two identical wedges, turning in different directions at the same angles, form a wedge with a variable beam deflection angle.

Prism cube. It consists of two rectangular prisms glued together with hypotenuse faces, on which there are reflective coatings. The prism cube makes it possible to change the direction of the sighting beam by more than 180˚.

Dove prism, or direct vision prism. This prism wraps the optical image from top to bottom. A Dove prism is used to rotate the image around the viewing axis.

Pehan prism. Since the Dove prism has a significant length, compact devices for image rotation use a Pehan prism, which is a gluing together of a Schmidt prism and a half-pentaprism. The Pehan prism can also work in converging beams, but there is more light loss here, so it is used less often.

Liquid wedge. A cuvette with elastic walls, transparent windows, filled with a transparent, easy-to-flow liquid is used in optical image stabilization systems as an adjustable optical wedge. Depending on the inclination of the glass window, the sighting beam passing through the cuvette is deflected in one direction or another.

The number of optical elements used to stabilize the optical image is continuously increasing. Here we present only the main ones, the use of which in optical instrumentation has become traditional.

1.2 Digital image stabilization

Action digital stabilizer based on analysis of image displacement on the matrix. The image is read only from part of the matrix, thus leaving a supply of free pixels at the edges. These pixels are used to compensate for device offset. Those. When the frame shakes, the image moves across the matrix, and the processor detects the vibrations and corrects the image, shifting it in the opposite direction.

Digital stabilizers have no moving parts (in particular, optical groups of several lenses). This has a positive effect on reliability, since fewer elements are susceptible to failure. In addition, the use of digital image stabilizers allows you to increase the sensitivity of light-absorbing elements (matrix). Also, the response speed of a digital stabilizer can be higher than that of an optical stabilizer.

Digital stabilizers have a number of disadvantages compared to optical stabilizers; in particular, in poor lighting conditions, low-quality images are obtained. As the focal length of the lens increases, the efficiency decreases: at long focal lengths, the matrix has to make too fast movements with too large an amplitude, and it simply ceases to keep up with the “escaping” projection.

Thus, it is believed that matrix shift stabilization is less effective than optical stabilization.

2 Main technical characteristics

One of the main parameters characterizing the quality of operation of optical image stabilization systems is dynamic accuracy, which is determined by errors in optical image stabilization and errors in tracking the line of sight for the object under study.

The task of determining the accuracy of optical image stabilization comes down to measuring the angular deviations of the line of sight during angular and reciprocating portable movements of the base caused by the rolling of a moving object. In this case, it is necessary to take into account a number of specific features of the functioning of the system in systems of the class under consideration. These are, first of all, small values ​​of stabilization and tracking errors; the need to measure the accuracy of optical image stabilization directly on the optical element, which is connected to the system by a non-unit kinematic connection and oscillates in inertial space, the need to measure stabilization and tracking errors at different positions of the system and the optical element.

List of sources used

Line of sight stabilization and guidance system with increased viewing angles / V.A., Smirnov, V.S. Zakharikov, V.V. Savelyev // Gyroscopy and navigation, No. 4. St. Petersburg, 2011. P.4-11.

Automatic optical image stabilization / D. N. Eskov, Yu. P., Larionov, V. A. Novikov [etc.]. L.: Mechanical Engineering, 1988. 240 pp.

Stabilization of optical devices / A.A. Babaev-L.: Mechanical Engineering, 1975. 190 p.

Cameras in smartphones have a constant tendency to improve. Now smartphone modules are acquiring additional functions that were previously available only to high-end cameras. Optical image stabilization (OIS) is a good example - it makes images look sharper and smoother. In this material we will learn in more detail what this function is and how it works, and you will understand how much it will be needed in your next smartphone.

Optical image stabilization first appeared in commercial devices such as compact cameras and SLR lenses in the mid-90s. Thanks to it, users were able to take better photos without using a tripod. OIS works by moving optical elements to counteract camera shake, thereby reducing image blur.

Subsequently, twenty years later, this function reached flagship smartphones. Since the sensors in modern mobile devices are much smaller than those in traditional cameras, it takes some effort to get enough light in adverse conditions.

During operation, the camera detects the movement of the smartphone using special sensors (gyros and computers), and directs the movement of the lens to counteract external factors. The lenses move from side to side or up and down. There's also digital stabilization, which uses software to reduce the impact of movement.

And despite its features, iOS can't do anything if an object is moving too fast to capture it. The function can improve the image only if the hand you are shooting with shakes. This leads to clear advantages of optical image stabilization during video recording. Of course, it is possible to smooth out a video in various video editors, but it will take quite a lot of time and it is quite possible that the desired result will not be obtained.

OIS requires a larger camera module, which is why it is currently found in larger smartphones. Among such recent examples are the Samsung Galaxy S7 and S7 Edge and the LG G5. It is also interesting that the large iPhone 6 Plus and Plus 6s have OIS in their arsenal, while regular-sized models do not have this feature. It is likely that the small size of regular iPhones is to blame for this fact.

Camera manufacturers list equal equivalent shutter speeds on their products. This way, camera buyers have the ability to compare, unlike smartphone buyers. Manufacturers of the latter do not seem to want to repeat a similar experience and simply note only the presence or absence of OIS in their device.

Camera shake is one of the significant factors affecting the quality of video material.

Before the advent of optical stabilization systems in Canon lenses, the only way to get around this limitation was to use tripod. This is the right approach when filming in any conditions, but using a tripod in some cases does not provide efficiency and mobility.

In order to overcome this limitation, Canon has developed a unique optical image stabilization system.

It must be said right away that the stabilization system is optical and, although it uses gyroscopes, they are tiny and only as sensors for detecting lens movement, so there are no kilogram rotating metal pancakes and a wearable tank battery and electric motor for their rotation. I would also like to note that, contrary to popular belief, this device does not consume a large amount of camera battery power. Although if you force it to work for hours, the energy consumption will be noticeable.

How does Image Stabilizer (IS) work?

The image stabilizer moves a group of objective lenses in a plane parallel to the film. When the lens moves due to shock, the light rays from the object (its image) shift along the optical axis, causing a blurred image.

By shifting the group of stabilization lenses in a plane perpendicular to the film plane within the required limits to compensate for lens movement, you can achieve an effect where the rays reaching the film plane actually remain stationary. The picture shows how the path of rays is mechanically corrected in the case when the lens “pecks”.

Camera movements are captured by two gyroscopic sensors. Sensors determine the direction (angle) and speed of movement (shake) of the camera and lens, which usually occurs when shooting handheld. To protect gyrosensors from errors associated with the reaction to the movement of the camera mirror or the shutter, the sensors are enclosed in special protective blocks

The lens group of the stabilization unit has a direct drive from the cores (solenoid). The device is small, lightweight, consumes more than a moderate amount of energy, and has a short response time - a quick response to commands. The device allows you to effectively compensate for vibrations with a frequency from 0.5 to 20 Hz. The position of the stabilization unit is determined using infrared emitter LEDs (IREDs - Infrared Emitting Diodes) on the frame of the unit and a position determination device (PSD-Position sensing Device) located on the electronics board of the unit. Thus, initially the stabilization device has feedback for precise positioning. The stabilization device also has a locking mechanism that sets the stabilization lens group to a central neutral position when the image stabilization device is turned off.