Electronic shutter. Silent mode can ruin your photos - stanislav vasiliev
The shutter of the camera is a special mechanism that is needed to transmit light to the camera matrix for the desired period of time (exposure).
Gate designs are many and varied. The most common curtain shutter, consisting of two fabric or metal curtains, which at the time of shooting form a gap of different widths between them (depending on the shutter speed), which “runs” along the frame, allowing the right amount of light to enter the matrix.
Shutter speed is the time during which the camera's sensor is exposed to light passing through the lens.
An example of a camera shutter
The shutter speed is indicated in seconds, while they are indicated by a number with a double prime ("") instead of a decimal point, symbolizing the second (2""5, 0""8), or, much more often, in fractions of a second, and only the denominator is indicated, and the numerator is taken equal to 1, that is, a shutter speed of 60 means a time of 1/60 of a second. The symbol “B” (from the English word “Bulb”) means that the camera matrix will be open to light for an unlimited time. When the photographer presses the shutter button, the shutter opens. When the button is pressed a second time, the shutter closes. With this function, you can get exposures of several hours, which can be useful when photographing the starry sky.
electronic shutter
In early film cameras, the shutter was a mechanical device. In modern digital cameras, the shutter is made in the form of an electronic circuit that controls the process of reading information from the matrix. For ease of understanding, the electronic shutter can be represented as a special electronic circuit that supplies voltage to the matrix for a certain time (hold), while the rest of the time the matrix is de-energized.
An electronically controlled mechanical shutter is often referred to as electronic.
Depending on the method of reading information from the matrix, two types of electronic shutters are distinguished: a vertical shutter (Global Shutter, the picture is formed completely) and a rolling shutter (Rolling Shutter, progressive reading technology).
With a vertical shutter, a digital image is formed instantly, just like when photographing, i.e. all pixels of the matrix allocated for work transmit information simultaneously. The operating time of the sensor is equal to the shutter speed, which is set in the camera in advance.
With a rolling shutter, a digital image is built not by instantaneous reading of information from the matrix, but by its sequential scanning. Those. information from the sensor is not transmitted all at once, but line by line - from top to bottom, while the shutter seems to slide across the frame. Again, the concept of a shutter here is arbitrary and has nothing to do with the mechanical implementation.
Simplified operation of electronic shutters can be shown in the following pictures:
The use of an electronic shutter makes it possible to achieve fast shutter speeds without the use of expensive high-speed mechanical shutters.
One of the main mechanisms of digital cameras is the shutter, its functional purpose is to pass, when the button is pressed, light rays to the matrix, which is a photosensitive element. Light rays are transmitted for a certain period of time. This period of time during which the shutter opens is called " excerpt". A feature of digital devices is the installation of shutters that can close and open at a very high speed, thanks to which the exposure time (matrix illumination) is regulated with high accuracy. For specialists, it is very important that photographic equipment has such accuracy, as well as a large range. With a slow shutter speed, more light enters the matrix. The shutter of modern digital cameras, especially for professional use, can control shutter speed well. At the same time, this element protects the matrix from flare, which can occur when reading an image, at the very beginning of the exposure.
Gate types
Closures may have differences in their design, as well as in the principle of closing. According to such features, these elements are divided into electronic and mechanical. In various models of digital cameras, an electronic shutter is installed; it is built directly into the camera sensor.
electronic shutter
At the right moment, it turns on the sensor to receive the light flux, then turns it off at the command of the processor. The operation of such a shutter is controlled by the camera's processor, its electronic equipment. When using such an electronic element, the light flux constantly hits the matrix, due to which the image from the matrix is transmitted to the LCD display of the digital device. Such an image is read in a certain time, which lasts between zeroing the matrix and the moment when the electronic information is read. This time is the shutter speed, which is characterized by the camera. Thanks to electronic shutters, the photographer can use fast shutter speeds, even up to 1/15000s. The operation of the electronic shutter is characterized by the absence of noise and vibration. The only thing is that when using such a shutter, you can also observe low image quality, since the reading of the matrix cells occurs sequentially. In order to avoid image distortion, such unpleasant effects as a halo, blooming, professional photographic equipment is also provided with a mechanical shutter.
mechanical shutter
Provides additional protection of the matrix from the ingress of fine dirt and dust. It also performs such an important function as dosing light on the photosensitive element of the camera, that is, on the matrix. Thanks to the mechanical shutter, the expensive matrix retains its high technical qualities. Such a shutter is characterized by a certain service life.
Mechanical shutters are also divided into two groups - curtain and central.
Central shutter
Represents the structure of thin plates ( petals), opening towards the edges and closing in the opposite direction, so the luminous flux is distributed evenly. It is installed between the lenses of the objective. The most valuable for professionals are those valves in which the dampers open very quickly.
curtain shutters
They have higher speed and greater instantaneous exposure. The curtain shutter design uses two parts (curtains), which are separated by a gap. The light flux penetrates into it from the lens. When the slit shutter is triggered, its first curtain opens the frame window, the second closes it. The shutter speed depends on the width of the gap that is formed between the curtains. The principle of operation of the curtain shutter, in which the curtains move, can lead to distortion of some subjects in the picture. But this shutter provides processing of short exposures and has a high coefficient of action.
Electronic shutter
In digital cameras, an electron-optical shutter can also be used, which is a liquid crystal located between two polarized plates. A light flux flows through this crystal, then it enters the optical converter.
The shutter is an important element in the operation of any photographic equipment. The basic principle of operation of any kind of shutters is the opening during photography, the passage of light rays. When the light flux hits the photosensitive element, the frame is exposed. The next step is to close the shutter, which allows you to proceed to the next shot. The shutter plays a very important role in the design of a camera.
Both a conventional film camera and a modern digital camera have an optical lens system, a diaphragm, and a shutter. It can be said that from the point of view of the basic scheme of operation of a photographic device, little has changed with the advent of digital photographic equipment: light rays are collected in the lens and then directed through the hole (diaphragm) to the photosensitive element (sensor). In this scheme, the shutter and aperture are elements invisible to the photographer's eyes, which, nevertheless, have a huge impact on the result of the shooting. Why were these elements, well known from film cameras, preserved in modern digital photographic equipment? What are they needed for? How do aperture and shutter work in a digital camera?
The purpose of the shutter and aperture
Gate- this is one of the main mechanisms of a digital camera, which is responsible for transmitting light rays to the photosensitive element (matrix) for a specified period of time when the photographer presses the shutter button. The main purpose of the shutter is to regulate the duration of the passage of the light flux through the optical system of the camera.
The time that the camera shutter opens is called shutter speed or exposure time. If the shutter speed is less than a second, then it is indicated as a denominator of a fraction, denoting a fraction of a second. For example, 1/125 of a second or 1/30 of a second. The shutters installed in digital cameras are able to close and open at high speed, thereby adjusting the exposure time of the matrix, that is, shutter speed, with high accuracy.
The slower the shutter speed, the more light will hit the photosensitive element of the camera. From a photographer's point of view, a camera shutter must be highly accurate, reliable in various shooting conditions, and have a wide shutter speed range. In modern digital cameras, the shutter is used not only to control shutter speed, but also to protect the sensor from flare during image reading or before exposure.
Diaphragm is a round variable hole that is located inside the camera lens. The photographer can vary the diameter of the hole, thereby adjusting the flow of light entering the matrix of the digital camera. The size of this aperture is determined by the aperture value: the larger the aperture aperture (small aperture number), the more light falls on the matrix and vice versa.
In digital cameras, the aperture value can be changed within a fairly wide range, for example, for the Tamron AF 18-270mm f / 3.5-6.3 Di II VC lens, from f / 3.5 to f / 6.3. In addition, the aperture also affects the depth of field of the imaged space, allowing the photographer to control the creative process. As already clear, shutter speed and aperture are interdependent parameters. Together they form the so-called expocouple: Decreasing one of these parameters increases the other.
Photographic shutter: principle of operation and types
The moment a photograph is taken, the shutter of the camera opens. Light rays pass through the lens, hit the diaphragm, which controls the amount of light, and eventually reach the photosensitive element. After the light directly hits the matrix of a digital camera, the exposure of the frame begins. Then the shutter closes. In a moment, the camera will be ready to shoot the next frame. Opening and closing, the shutter, like the diaphragm, provides a change in the amount of light falling on the matrix.
Naturally, no matter how perfect a photographic shutter is, it requires a short, but still some period of time in order to open. It also takes some time to close. In this regard, three stages or phases can be distinguished in the operation of a photographic shutter.
The first phase is associated with the opening of the active aperture of the lens. The next one is already the phase of full opening of the active hole. And, finally, the last phase is the closing phase, that is, a certain period of time from the beginning of the reduction of the active hole to its complete closure. From this it can be understood that during this entire shutter cycle, the actual lens aperture remains fully open only some of the time.
In this regard, one of the most important characteristics of the shutter is optical efficiency(EFFICIENCY), which determines the ratio of the amount of light that has passed during the operation of the shutter, to the amount of light that could pass through the "ideal" shutter in the same period of time. The more the efficiency value approaches unity (i.e. 100%), the more perfect the shutter works. In other words, the less time it takes for a given shutter speed to open and close the shutter, the longer the lens opening will be fully open, which means more light will pass through the lens. In this regard, we can say that a good photographic shutter is able to fully reveal the aperture ratio of the lens.
All digital camera shutters have special controls that allow you to set the shutter speed required for a given photograph. However, a suitable shutter speed can be determined automatically by the camera. Many devices have a special mode of fully manual control of the shutter opening time (Bulb), through which the shutter can not only open, but also close strictly at the command of the photographer. This mode is very relevant when shooting at slow shutter speeds when the camera is mounted on a tripod.
According to their design and principle of operation, shutters in digital cameras are divided into the following types:
- electronic shutter
If film cameras had a mechanical shutter that opened and closed shutters, limiting the effect of light on the film, then in digital cameras its role is played by an electronic shutter. Almost all digital cameras are equipped with just such an electronic equivalent of the shutter, which is built right into the camera sensor.
It is a kind of switch that turns on the sensor to receive the light flux at the right time and turns it off at the command of the processor. The electronics and processor of the camera completely control the operation of such a shutter. A feature of the electronic shutter is that the light hits the matrix constantly, which makes it possible, in particular, to transfer an image from the matrix to the camera's LCD display. When the electronic shutter is activated, the image from the camera matrix is read for a certain period of time. This interval between zeroing the matrix and the moment of reading electronic information from it is in this case the exposure time.
The advantage of using electronic shutters in modern digital photography is that they can achieve very fast shutter speeds. Such a shutter, in particular, is able to work out shutter speeds up to 1/8000 or 1/15000 s. In addition, the electronic shutter operates silently and vibration-free.
However, it also has its drawbacks. This is, first of all, low quality associated with various image distortions, the cause of which is the sequential reading of the matrix cells. Due to constant exposure to light, the electronic shutter is prone to ghosting, blooming, and other unpleasant effects. That is why in advanced compact cameras and professional digital cameras, in addition to the electronic shutter, there is always a traditional mechanical shutter. In cheap models of digital cameras, only an electronic shutter is used.
Despite the advent of digital photography with electronic shutters controlled by powerful processors, the mechanical shutter is not a thing of the past. It is still used in decent digital cameras, only now it is paired with an electronic one. Synchronous operation of these two shutters makes it possible to achieve fast shutter speeds and at the same time avoid the appearance of halo around contrasting images. In professional SLRs and advanced compacts, the electronic shutter is used only for ultra-short shutter speeds, while the mechanical one mostly works.
In addition to the fact that the mechanical shutter doses the light falling on the photosensitive element of the camera, it also serves to additionally protect the matrix from dust and dirt. After all, the matrix is the most expensive element of a digital camera, especially when it comes to a professional camera. The mechanical shutter itself has a certain resource of work and over time it fails.
According to their design, mechanical shutters are traditionally divided into two types - central and curtain (curtain-slotted) shutters. The central shutter is usually installed between the lenses of the objective. It uses shutters in the form of thin petals, which open the light aperture of the lens from the optical axis to the edges, and close it in the opposite direction. This ensures uniform distribution of illumination over the entire field of the frame. The central shutter has the highest efficiency, in which the light-shielding shutters operate at the highest speed.
The central shutter has quite a few advantages: no image distortion as a result of operation, even distribution of illumination and good resistance to temperature fluctuations. However, compared to curtain shutters, central ones have a lower efficiency and a lower minimum speed, that is, a lower instantaneous exposure.
As for the curtain or curtain-slot shutter, it uses an opaque shutter, consisting of two parts separated by a transverse slot. It is through this slit that the light coming from the lens enters. When the shutter is actuated, the shutters move one after the other: the first light shutter opens the frame window, and the second, respectively, closes it. The shutter speed here depends on the width of the slit.
The main advantages of a curtain shutter are its high efficiency (it can reach 95%) and the ability to work out fast shutter speeds (up to 1/1250 s in some models). But when shooting fast-moving objects, the use of a curtain-slit shutter often leads to shifting and distortion of individual elements of the image. Curtain shutters are also characterized by the fact that they are more susceptible to temperature fluctuations.
— Electron-optical shutter
Along with the electronic shutter, some models of digital cameras use an electro-optical shutter rather than a mechanical shutter. This is a liquid crystal that is located between two parallel polarized plates. Through it, the light flux passes to the electro-optical converter of the camera. When a voltage is applied to the thin electrically conductive coating of the inner surface of the plates, an electric field arises that changes the plane of polarization of the liquid crystal by 90 degrees. As a result, the maximum opacity of the crystal is ensured and, as a result, the liquid crystal shutter is closed. In the absence of voltage, light through the liquid crystal enters the matrix. Since there are no mechanical elements here, the electro-optical shutter is characterized by rather high reliability and simplicity.
digital camera aperture
The diaphragm in its classical form is arranged as an opaque shutter formed by thin metal petals moving towards the center of the lens. This is the so-called iris diaphragm. Thin petals, placed in a circle along the rim of the lens, rotate and, thereby, increase or decrease the opening through which light enters. The more the aperture blades are open, the more light passes to the photosensitive element. Aperture control in digital cameras can be carried out in manual or automatic modes.
Manual aperture control is usually implemented in the form of a ring on the outer surface of the lens barrel, on which the aperture number scale is marked. When the aperture ring is rotated, the petals move. In this case, each transition from one value of the f-number to the neighboring value provides a change in the amount of light passing through the lens exactly twice. Aperture priority mode is very convenient, when you can set the aperture yourself, and the camera will set all other shooting parameters automatically. The control of the aperture in automatic mode is carried out by means of the camera electronics, based on the analysis of the specific conditions of photography.
Changing the aperture affects two key image properties at once - aperture and depth of field. Aperture refers to the maximum amount of light that a given lens can transmit. In daylight conditions, adjusting and controlling the aperture of a digital camera is not difficult. But in low light conditions, such as when shooting in a dark room, the photographer has to shoot with a large aperture so that the photo does not turn out dark. This requires flexible aperture control to compensate for the lack of light.
The size of the aperture also determines the area that will look sharp in the photo. In other words, the aperture determines whether the background in the picture will be blurry or sharp. For example, a small aperture is used to blur the background and perspective. Depth of field extends from the center to the edge of the image, respectively, the closer to the edge of the image, the more blurred the object will be. On the contrary, a large aperture is used in cases where everything in the photo needs to look sharp. In general, aperture control provides the photographer with complete freedom of action and a wide field for creative experiments.
Speaking of the shutter and aperture of a digital camera, it should be noted that in some modern cameras, the aperture can be combined with a central leaf shutter. In this case, the aperture mechanism operates exactly at the moment the shutter is released, and the shutter blades at the same time move apart to a distance that corresponds to the set aperture value. But such combined shutters-diaphragms with regulation of the size and duration of the opening of the light hole are installed mainly in entry-level cameras. Although they provide greater compactness of photographic equipment.
The problem is that, due to its design, the combined shutter-aperture mechanism is only able to work out exposure pairs like a long shutter speed - the minimum relative aperture or a short shutter speed - the maximum relative aperture. Such linearity of exposure parameters results in the fact that, for example, in low light conditions, the camera will use long exposures with an open aperture, which, of course, will negatively affect the quality of the photographic image. In addition, aperture shutters are not capable of providing a wide range of shutter speeds and apertures.
The shutter and diaphragm remain the main mechanisms of the photographic apparatus in the digital age. Along with the characteristics of the lens, the shutter and aperture largely determine the quality of the photographic image. The ability to manually adjust aperture and shutter speed gives the photographer room to be creative and fine-tune their digital camera to suit specific shooting conditions.
Shutter performance is one of the most important parameters a photographer controls to capture the moment. With the advent of electronic shutters for mirrorless cameras, a lot of additional options appeared in the settings menu and people began to often ask questions about what's what and why. In this article, I would like to describe in detail the principles of operation of camera shutters in order to understand what settings are needed for what and what limitations arise when working with certain types of shutters.
So, first we need to understand a little theory. The shutter is a device that limits the access of light to the matrix (or to the film, but we will not consider this technique now). Shutters can be "mechanical" (to put it correctly, it's still "electromechanical", because the time of pure mechanics has already passed, but for simplicity they are reduced to "mechanical"), "electronic" and all kinds of "combined", to varying degrees combining the principles mechanical and electronic shutters.
1. Mechanical shutter
Most often, modern cameras use a mechanical focal shutter, which stands directly in front of the matrix. There is also a central shutter, which, as a rule, is located in the lens, but we will not talk about it today, because now it is quite rare and, as a rule, in medium format systems (for example, in compact cameras, the central shutter is found in X100 series cameras from FUJIFILM, as far as I know, and in similar models).
If greatly simplified, then, in fact, the focal plane shutter is two curtains. One opens access to the matrix, and the second, respectively, closes. Well, if you get a little tedious, then it would be more correct to call this design like this: an electronically controlled focal shutter of a curtain-slit type with a vertical stroke of the shutters. But we're not boring, right? ..
If we talk about SLR cameras, then the matrix is not involved at the time of building the frame, a system of mirrors and a prism helps us with sighting. Therefore, at the time when we aim and build a frame, for SLR cameras the shutter is closed and ready to shoot. When the shutter button is pressed, the mirror rises, the shutter opens (the first curtain moves, opening up light access to the matrix). And when the desired shutter speed is reached, the shutter closes (the second curtain falls, closing the matrix). Here's a video of how the whole system works:
But, since we are talking about mirrorless cameras, here everything is a little different. At the moment when we are building a frame, the matrix is involved, it works - a signal is read from it and sent to the screen or to the electronic viewfinder. Accordingly, the shutter must be constantly open. At the moment when the shutter button is pressed, the shutter on the mirrorless camera first closes, and then the process proceeds in exactly the same way as described above: the first curtain opens up light access to the matrix, and the second closes it. Here you can see how this happens using the FUJIFILM X-Pro1 shutter as an example (in fact, the camera model is not so important, everything works in principle the same way for other mirrorless cameras):
The mechanical shutter is well known from film cameras; it is a technologically advanced design. It is clear how to work with her. However, such a shutter has a number of limitations. And the worst ones are:
- the speed of the entire node is determined by the speed of the shutters
- the impossibility of setting very short shutter speeds
- vibrations introduced into the system by moving parts of the shutter
- The shutter makes a loud noise during operation
In principle, new ultra-light and ultra-strong materials could help in the first case, and the speed of the shutters can be increased. However, in reality, the strength of the knot is not the only limit that prevents further development of the shutter mechanism. This is where it is worth talking about the second limitation, which in fact turns out to be much more unpleasant than the first. The fact is that if the shutter speed is quite long, then the shutter will work it like this: the first curtain opens completely -> light falls on the entire surface of the matrix -> the required shutter speed is reached -> the second curtain closes, interrupting the light flux. But if you want to set faster shutter speeds, then the shutter starts to work differently: the first curtain opens, providing light to the matrix -> only part of the matrix is open, but the fast shutter speed has already been reached -> the second curtain starts to close when the first one has not fully opened. That is, in fact, at short shutter speeds, the shutter does not open the entire matrix, but only part of it - the slit "runs" along the sensor, exposing the frame. The narrower the slit, the less light hits the matrix and the faster the shutter speed provides. This is how it looks like:
But here's the problem: if the gap is very, very thin, then, in addition to problems with the exact synchronization of the movement of the curtains themselves, there is also a diffraction effect that significantly worsens the quality of the resulting image. That is why, on most cameras, the fastest shutter speed with a mechanical shutter is usually 1/8000 of a second. Which means that the second curtain starts to move after the first with a difference of 1/8000 of a second.
By the way, due to the curtain-slit principle of the mechanical shutter, certain problems arise when shooting with flashes. The fact is that most flashes have a fairly short pulse length. That is, in simple terms - the flash lamp shines very brightly, but for a short time. As a rule, the pulse lasts from 1/800 to 1/40000 of a second, depending on the power. If the shutter speed is quite long, then the shutter opens the entire matrix, and then a short flash pulse is exposed over the entire sensor area. But if you want to use a shorter shutter speed, then it will already be determined, as we remember, by the movement of the shutter slit along the matrix. And the light from a short flash pulse will only expose a small area of the sensor. Therefore, not the entire frame will be illuminated, but only part of it. Therefore, when shooting with flashes on cameras, restrictions on short shutter speeds are introduced: with the flash turned on, you simply cannot use shutter speeds at which not the entire matrix is open. This limitation can be circumvented by using flashes that have a "high speed sync" mode. With it, the pulse is weaker in power, but lasts as long as necessary to expose the entire frame by the moving shutter slit.
The third point is shutter shock during operation, the so-called shutter shock. No matter how light the shutter curtains are, they still have weight and when moving they accelerate and decelerate, causing the system to oscillate. If at short shutter speeds small fluctuations do not interfere with the photographing process, then at moderately slow shutter speeds these vibrations already lead to microblurring and, as a result, to a drop in the quality of the resulting image. And, by the way, the larger the camera megapixel, the more it will be noticeable. Engineers are working on damping vibrations, but here one must understand that they cannot cancel the laws of physics. Here, by the way, in this slow motion video, you can very well observe the fluctuations of the shutter curtains:
Well, and finally - the mechanical shutter makes noise during operation. The same "chick-truck" that we hear when shooting. In a SLR camera, mirror clapping is also added here. But even mirrorless cameras with a mechanical shutter are by no means silent. Not all shoots allow this. For example, in theater or wildlife photography, the sound of a mechanical shutter can be quite annoying.
So, to summarize, the mechanical shutter has undeniable advantages:
- its design is clear, it has been well developed over the years
- wide range of shutter speeds available (theoretically from infinity to 1/8000 second)
- inability to use very short shutter speeds
- shutter shock
- sounds at work
- mechanism wear
2. Electronic Signer
When using an electronic shutter, the matrix is not closed by any shutters, it always remains open. It's just that when the shutter button is pressed, the charge on the photosensitive elements is reset, the signal recording starts, and then, after a specified time, it is read. To put it even more simply, the matrix turns on to register light and turns off at the end of the exposure. All smartphones are equipped with an electronic shutter, for example. Recently, this type of shutter has become quite common on large mirrorless cameras.
Benefits of electronic shutter:
- can achieve very fast shutter speeds (up to 1/32000 for FUJIFILM X-series cameras)
- he is absolutely silent
- there is not even the slightest shaking of the apparatus from the movement of the shutter parts
- does not consume the resource of the mechanical shutter, because the curtains do not work
- it is compact, it has no moving parts
- rolling shutter effect
- banding when shooting with flashing light sources
- inability to work with flash
The solution to the problem of rolling shutter can be the so-called global shutter, "global shutter". This is a kind of electronic shutter, in which data from the matrix is read not line by line, but at the same time. The difficulty of implementing a global shutter is that now the data flow from the matrices is so large that expensive solutions are required to read them in one sitting. Therefore, for now, the global shutter is used only in those systems where it is vital and where the price of equipment is not such a critical factor. For example, the global shutter is most widely used in digital cinema cameras - rolling shutter is unacceptable there, and the high price of the solution is not so noticeable against the background of the overall budget of the movie.
Second. Flashing and flashing light sources (photo flashes, lightning bolts, computer monitors, flickering fluorescent lights, and so on) can leave stripes on the frame. That is, one part of the image is much weaker illuminated than the other. The boundary between these two parts is usually very sharp. The effect occurs for the same reason as the rolling shutter. An explanation of it and an example frame can be found at the above Wikipedia link. Because of this effect, flashes cannot be used with an electronic shutter (the "Flashes" item in the menu is disabled when an electronic shutter is selected) and should not be shot in a studio. By the way, the effect does not always occur - it usually does not occur at relatively long shutter speeds.
In summary, the electronic shutter is a rather interesting solution, but so far, due to technological limitations, it is applicable either in cases where a very fast shutter speed is required, or where the sound accompanying the operation of the camera mechanisms is unacceptable.
3. Hybrid
And finally, we got to hybrids, in which they try to combine the advantages of the first two types of shutter and avoid their disadvantages. In this part, let's talk about the shutter with the "electronic front curtain" (Electronic Front Curtain Shutter). When using the electronic front curtain shutter function, the mechanical front curtain is not applied. Instead, an electronic exposure of the image sensor is started (as with an electronic shutter), which is completed by the mechanical closing of the rear shutter curtain. That is, it turns out half electronic, half mechanical shutter. What does it give us? And here's what:
- mirrorless camera does not waste time closing the shutter before shooting
- during exposure, there is no shaking of the system from the movement of the shutters
- shutter sound decreases (only one of the two curtains moves)
There are several nuances to an electronic front curtain shutter. First, when shooting at a fast shutter speed (typically at shutter speeds faster than 1/2000 second) and wide open apertures, a blurred area may appear in the image. It doesn't have to be, but it can. Secondly, in the same way, when shooting at a fast shutter speed (shorter than 1/2000 second), depending on the shooting conditions, the image brightness may be uneven. Alas, these are the costs of "combination" - the shutter mode with an electronic front curtain, albeit to a lesser extent, inherits the "sores" of the electronic shutter. And thirdly, if the lens is made by another manufacturer, then when shooting with a shutter with the first electronic shutter, it is likely that you will not be able to set the correct exposure or the image brightness will again be uneven. In all such cases, you need to switch to another type of shutter, for example, to a mechanical one.
So, now that we have dealt with the theory, we can already start explaining how shutter modes work using the example of the FUJIFILM X-H1 camera. There are several of them, you can choose from the following list:
- Mechanical (MS) . By default, the shutter speed is from 30 seconds to 1/8000 second, but in shutter priority (S) and manual (M) modes, the shutter speed can be set from 15 minutes to 1/8000 second, and in bulb (B) mode, the maximum shutter speed can reach 60 minutes. Good old mechanics! Use is recommended in most cases, especially when shutter sound is not critical, when very fast shutter speeds are not needed, and when the goal is not to clearly stabilize the image. You must also switch to this type of shutter if you are shooting with flash or in the studio.
- Electronic (ES) . By default, from 30 seconds to 1/32000 second, and also in S and M modes, it can be from 15 minutes to 1/32000 second. The mode is completely silent and allows you to use very fast shutter speeds. But, alas, it is prone to rolling shutter and the appearance of stripes when shooting with flickering light ... Therefore, this type of shutter is recommended only in cases where complete silence is needed or when very fast shutter speeds are required. At the same time, it is highly desirable not to shoot dynamic scenes and avoid flickering lighting (it is given, for example, by fluorescent lamps). Also, this shutter mode is used in situations where you want to get the most out of image stabilization systems, such as when shooting at extra slow shutter speeds handheld, without a tripod, or when shooting at slow shutter speeds. By the way, it is in this mode that the maximum rate of fire of the camera is achieved - up to 14 frames per second!
- (EF) . Exposure from 30 seconds to 1/8000 second, but in modes S and M can be from 15 minutes to 1/8000 second. This type of shutter can be used in photography when it is necessary to shorten the time between pressing the shutter button and taking the picture. This mode can also be set when a well-stabilized image of single shots is required. In fact, this is the ideal reportage shutter mode: fast, quiet, with good stabilization. The only thing to consider is that the best image quality in this mode is achieved at shutter speeds up to 1/2000 second, so it is not recommended to shoot at very fast shutter speeds with this type of shutter. However, for most reportage stories, 1/2000 of a second is more than enough.
- Mechanical + Electronic (M + E) . In this case, from 30 seconds to 1/8000, the camera will shoot using a mechanical shutter, and at shutter speeds shorter than 1/8000 second, the electronic shutter comes into play, up to 1/32000 second. That is, the electronic shutter only works when the mechanical shutter can no longer cope with the speed. A very convenient combination for shooting with high-aperture optics with an open aperture. This is especially true in combination with dynamic range expansion modes, which require higher ISO values for FUJIFILM cameras. That is, this is an ideal mode for shooting with fast apertures with an open aperture and maximum expansion of the dynamic range, while you can easily shoot in the daytime, the camera does an excellent job with such scenes on this combination of shutter modes.
- With electronic front curtain + Mechanical (EF + M) . Here, from 30 seconds (or 15 minutes in S and M) to 1/2000, the shutter with an electronic front curtain will work, and after 1/2000 and up to 1/8000, a mechanical shutter will come into play. Convenient mode for reportage photography. At the most popular shutter speeds (up to 1/2000), a quieter, faster and less vibration-loaded shutter with an electronic front curtain will work, and at shorter shutter speeds a mechanical shutter will come into play.
- With electronic front curtain + Mechanical + Electronic (EF + M + E) . From 30 seconds (or 15 minutes in S and M) and up to 1/2000, the camera will shoot with an electronic front curtain shutter, after 1/2000 and up to 1/8000 the mechanical shutter will work, and at shutter speeds shorter than 1/8000 and up to 1/32000 there will be an electronic shutter in the case. Combo! Everything at once. Perhaps, for X-H1 this is the most interesting mode.
In all combined modes (like "EF + M + E") switching to one or another type of shutter will occur automatically, based on the required shutter speed when exposing the frame.
Modern digital cameras use curtain-slit focal shutters with vertical shutters. This means that such a shutter is located immediately in front of the camera's matrix, consists of curtains that move vertically (usually from top to bottom and back).
Below is a visual representation of how the shutter is released:
Video 1.
Pay attention to how much shakes the mirror after its rise and return, as well as how shutter curtains tremble monstrously. The video shows that the shutter curtains consist of several parts (the so-called slats or 'blinds').
Video 2.
In this video, you can see the gap that is formed during the movement of the shutter curtains.
Video 3.
Full frame camera and cropped camera.
Video 4.
It shakes not only the mirror and shutter shutters, but also the aperture blades.
And a little reasoning about the shutter, using the example of a camera.
The timing of this camera is 1/200 of a second. This means that this is exactly the amount of time the shutter curtains need to cover a distance equal to the height of the sensor.
If you need to shoot at shutter speeds longer than or equal to synchronization, then the shutter will work as follows:
- The first curtain opens, it takes 1/200 of a second.
- It is carried out, at this time the matrix remains completely open. Let's take a shutter speed of 1/60 second as an example. The second curtain will start moving 1/60 of a second after the first curtain starts moving.
- The second curtain closes, it takes 1/200 of a second.
- The curtains rise together to the initial position.
At these shutter speeds, it is easy to synchronize the flash and the shutter. Typically, the flash fires after the first curtain (as soon as the shutter fully opens the sensor), or before the second curtain starts moving (before the shutter closes). For example, my Nikon flash pulse has a duration of 1/800s to 1/40.000s depending on power. When the flash fires, the camera matrix is fully open and there are no problems with synchronization.
If you need to shoot at shutter speeds faster than sync, the shutter will work as follows:
- The first curtain opens.
- The second curtain does not wait for the full opening of the matrix and starts its movement after the first one. The delay of the second curtain just determines the time. Let's take as an example the fastest shutter speed allowed for - 1/4000 s. In this case, the second curtain starts moving 1/4000s after the first curtain starts moving, and thus the two curtains move together to form a moving slit that produces the exposure.
- The curtains rise together to the starting position.
At such shutter speeds, it is difficult to synchronize the operation of the flash with the shutter. If the flash fires only at a certain moment, then in the picture we will get a stripe that is formed by the shutter slit. To get around this limitation, high-speed sync flashes are used, which “shine” the entire time both curtains are moving, to avoid banding.
Interestingly, if we are shooting at 1/60 of a second, then in fact the shutter needs much more time to do its job. So, it takes 1/60 s to lower the first curtain and wait for the second one, 1/200 s to move the second curtain and at least another 1/200 s to raise both curtains to their original position ( perfect case, in reality, more time is needed). Total 1/60 + 1/200 + 1/200 = 2/75 s. If you remove the restrictions on the operation of the mirror, aperture and camera processor, then in one second under ideal conditions it will be possible to shoot no more than 38 frames, and this is mechanical limitation of continuous shooting.
At the same time, cameras that use an electronic shutter, which does not need to waste time on the movement of the shutters, already now allow you to shoot at 60 frames per second in photo mode without any problems (look at as an example). Just imagine how useful it would be for photojournalists and sports photographers to photograph certain events at such tremendous speed. For example, the fastest DSLR for 2014, the Canon 1DX, shoots at a maximum of 14 frames per second, which is 4 times lower than the 60 fps of some electronic shutter mirrorless cameras. The only problem is that modern cameras with an electronic shutter have their drawbacks, for example, they suffer from 'rolling shutter', etc. and for now, one can only dream of an electronic shutter that has the positive qualities of a mechanical shutter and a huge shooting speed.
By the way, the “real” shutter speed is easy to calculate. The height of the matrix is 15.8 mm, the curtain travels this distance in 1/200 of a second, and its speed is 3.16 m / s or 11.38 km / h, which is quite a bit :)
Thank you for your attention. Arkady Shapoval.
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