QCamera Class
The QCamera class provides interface for system camera devices. More...
| Header: | #include <QCamera> |
| CMake: | find_package(Qt6 REQUIRED COMPONENTS Multimedia) target_link_libraries(mytarget PRIVATE Qt6::Multimedia) |
| qmake: | QT += multimedia |
| Instantiated By: | Camera |
| Inherits: | QObject |
Public Types
| enum | Error { NoError, CameraError } |
| enum | ExposureMode { ExposureAuto, ExposureManual, ExposurePortrait, ExposureNight, ExposureSports, …, ExposureBarcode } |
| enum class | Feature { ColorTemperature, ExposureCompensation, IsoSensitivity, ManualExposureTime, CustomFocusPoint, FocusDistance } |
| flags | Features |
| enum | FlashMode { FlashOff, FlashOn, FlashAuto } |
| enum | FocusMode { FocusModeAuto, FocusModeAutoNear, FocusModeAutoFar, FocusModeHyperfocal, FocusModeInfinity, FocusModeManual } |
| enum | TorchMode { TorchOff, TorchOn, TorchAuto } |
| enum | WhiteBalanceMode { WhiteBalanceAuto, WhiteBalanceManual, WhiteBalanceSunlight, WhiteBalanceCloudy, WhiteBalanceShade, …, WhiteBalanceSunset } |
Properties
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Public Functions
| QCamera(QObject *parent = nullptr) | |
| QCamera(const QCameraDevice &cameraDevice, QObject *parent = nullptr) | |
| QCamera(QCameraDevice::Position position, QObject *parent = nullptr) | |
| virtual | ~QCamera() |
| QCameraDevice | cameraDevice() const |
| QCameraFormat | cameraFormat() const |
| QMediaCaptureSession * | captureSession() const |
| int | colorTemperature() const |
| QPointF | customFocusPoint() const |
| QCamera::Error | error() const |
| QString | errorString() const |
| float | exposureCompensation() const |
| QCamera::ExposureMode | exposureMode() const |
| float | exposureTime() const |
| QCamera::FlashMode | flashMode() const |
| float | focusDistance() const |
| QCamera::FocusMode | focusMode() const |
| QPointF | focusPoint() const |
| bool | isActive() const |
| bool | isAvailable() const |
| bool | isExposureModeSupported(QCamera::ExposureMode mode) const |
| bool | isFlashModeSupported(QCamera::FlashMode mode) const |
| bool | isFlashReady() const |
| bool | isFocusModeSupported(QCamera::FocusMode mode) const |
| bool | isTorchModeSupported(QCamera::TorchMode mode) const |
| bool | isWhiteBalanceModeSupported(QCamera::WhiteBalanceMode mode) const |
| int | isoSensitivity() const |
| float | manualExposureTime() const |
| int | manualIsoSensitivity() const |
| float | maximumExposureTime() const |
| int | maximumIsoSensitivity() const |
| float | maximumZoomFactor() const |
| float | minimumExposureTime() const |
| int | minimumIsoSensitivity() const |
| float | minimumZoomFactor() const |
| void | setCameraDevice(const QCameraDevice &cameraDevice) |
| void | setCameraFormat(const QCameraFormat &format) |
| void | setCustomFocusPoint(const QPointF &point) |
| void | setFocusDistance(float d) |
| void | setFocusMode(QCamera::FocusMode mode) |
| void | setZoomFactor(float factor) |
| QCamera::Features | supportedFeatures() const |
| QCamera::TorchMode | torchMode() const |
| QCamera::WhiteBalanceMode | whiteBalanceMode() const |
| float | zoomFactor() const |
Public Slots
| void | setActive(bool active) |
| void | setAutoExposureTime() |
| void | setAutoIsoSensitivity() |
| void | setColorTemperature(int colorTemperature) |
| void | setExposureCompensation(float ev) |
| void | setExposureMode(QCamera::ExposureMode mode) |
| void | setFlashMode(QCamera::FlashMode mode) |
| void | setManualExposureTime(float seconds) |
| void | setManualIsoSensitivity(int iso) |
| void | setTorchMode(QCamera::TorchMode mode) |
| void | setWhiteBalanceMode(QCamera::WhiteBalanceMode mode) |
| void | start() |
| void | stop() |
| void | zoomTo(float factor, float rate) |
Signals
| void | activeChanged(bool) |
| void | cameraDeviceChanged() |
| void | cameraFormatChanged() |
| void | colorTemperatureChanged() const |
| void | customFocusPointChanged() |
| void | errorChanged() |
| void | errorOccurred(QCamera::Error error, const QString &errorString) |
| void | exposureCompensationChanged(float value) |
| void | exposureModeChanged() |
| void | exposureTimeChanged(float speed) |
| void | flashModeChanged() |
| void | flashReady(bool ready) |
| void | focusDistanceChanged(float) |
| void | focusModeChanged() |
| void | focusPointChanged() |
| void | isoSensitivityChanged(int value) |
| void | manualExposureTimeChanged(float speed) |
| void | manualIsoSensitivityChanged(int) |
| void | maximumZoomFactorChanged(float) |
| void | minimumZoomFactorChanged(float) |
| void | supportedFeaturesChanged() |
| void | torchModeChanged() |
| void | whiteBalanceModeChanged() const |
| void | zoomFactorChanged(float) |
Detailed Description
QCamera can be used within a QMediaCaptureSession for video recording and image taking.
You can use QCameraDevice to list available cameras and choose which one to use.
const QList<QCameraDevice> cameras = QMediaDevices::videoInputs(); for (const QCameraDevice &cameraDevice : cameras) { if (cameraDevice.description() == "mycamera") camera = new QCamera(cameraDevice); }
On hardware that supports it, QCamera lets you adjust the focus and zoom. This also includes functionality such as a "Macro" mode for close up work (e.g. reading barcodes, or recognizing letters), or "touch to focus" - indicating an interesting area of the image for the hardware to attempt to focus on.
camera->setFocusPointMode(QCamera::FocusModeManual); camera->setCustomFocusPoint(QPointF(0.25f, 0.75f)); // A point near the bottom left, 25% away from the corner, near that shiny vase
The minimumZoomFactor() and maximumZoomFactor() methods provide the range of supported zoom factors. The zoomTo() method allows changing the zoom factor.
camera->setZoomFactor(3.0);
After capturing the raw data for a camera frame, the camera hardware and software performs various image processing tasks to produce the final image. This includes compensating for ambient light color, reducing noise, as well as making some other adjustments to the image.
You can control many of these processing steps through the Camera properties. For example, you can set the white balance (or color temperature) used for processing images:
camera->setWhiteBalanceMode(QCamera::WhiteBalanceFluorescent);
For more information on image processing of camera frames, see Camera Image Processing.
See the camera overview for more information.
Member Type Documentation
enum QCamera::Error
This enum holds the last error code.
| Constant | Value | Description |
|---|---|---|
QCamera::NoError | 0 | No errors have occurred. |
QCamera::CameraError | 1 | An error has occurred. |
enum QCamera::ExposureMode
| Constant | Value | Description |
|---|---|---|
QCamera::ExposureAuto | 0 | Automatic mode. |
QCamera::ExposureManual | 1 | Manual mode. |
QCamera::ExposurePortrait | 2 | Portrait exposure mode. |
QCamera::ExposureNight | 3 | Night mode. |
QCamera::ExposureSports | 4 | Spots exposure mode. |
QCamera::ExposureSnow | 5 | Snow exposure mode. |
QCamera::ExposureBeach | 6 | Beach exposure mode. |
QCamera::ExposureAction | 7 | Action mode. Since 5.5 |
QCamera::ExposureLandscape | 8 | Landscape mode. Since 5.5 |
QCamera::ExposureNightPortrait | 9 | Night portrait mode. Since 5.5 |
QCamera::ExposureTheatre | 10 | Theatre mode. Since 5.5 |
QCamera::ExposureSunset | 11 | Sunset mode. Since 5.5 |
QCamera::ExposureSteadyPhoto | 12 | Steady photo mode. Since 5.5 |
QCamera::ExposureFireworks | 13 | Fireworks mode. Since 5.5 |
QCamera::ExposureParty | 14 | Party mode. Since 5.5 |
QCamera::ExposureCandlelight | 15 | Candlelight mode. Since 5.5 |
QCamera::ExposureBarcode | 16 | Barcode mode. Since 5.5 |
enum class QCamera::Feature
flags QCamera::Features
Describes a set of features supported by the camera. The returned value can be a combination of:
| Constant | Value | Description |
|---|---|---|
QCamera::Feature::ColorTemperature | 0x1 | The Camera supports setting a custom colorTemperature. |
QCamera::Feature::ExposureCompensation | 0x2 | The Camera supports setting a custom exposureCompensation. |
QCamera::Feature::IsoSensitivity | 0x4 | The Camera supports setting a custom isoSensitivity. |
QCamera::Feature::ManualExposureTime | 0x8 | The Camera supports setting a manual exposure Time. |
QCamera::Feature::CustomFocusPoint | 0x10 | The Camera supports setting a custom focus point. |
QCamera::Feature::FocusDistance | 0x20 | The Camera supports setting the focusDistance property. |
The Features type is a typedef for QFlags<Feature>. It stores an OR combination of Feature values.
enum QCamera::FlashMode
| Constant | Value | Description |
|---|---|---|
QCamera::FlashOff | 0 | Flash is Off. |
QCamera::FlashOn | 1 | Flash is On. |
QCamera::FlashAuto | 2 | Automatic flash. |
enum QCamera::FocusMode
| Constant | Value | Description |
|---|---|---|
QCamera::FocusModeAuto | 0 | Continuous auto focus mode. |
QCamera::FocusModeAutoNear | 1 | Continuous auto focus mode on near objects. |
QCamera::FocusModeAutoFar | 2 | Continuous auto focus mode on objects far away. |
QCamera::FocusModeHyperfocal | 3 | Focus to hyperfocal distance, with the maximum depth of field achieved. All objects at distances from half of this distance out to infinity will be acceptably sharp. |
QCamera::FocusModeInfinity | 4 | Focus strictly to infinity. |
QCamera::FocusModeManual | 5 | Manual or fixed focus mode. |
enum QCamera::TorchMode
| Constant | Value | Description |
|---|---|---|
QCamera::TorchOff | 0 | Torch is Off. |
QCamera::TorchOn | 1 | Torch is On. |
QCamera::TorchAuto | 2 | Automatic torch. |
enum QCamera::WhiteBalanceMode
| Constant | Value | Description |
|---|---|---|
QCamera::WhiteBalanceAuto | 0 | Auto white balance mode. |
QCamera::WhiteBalanceManual | 1 | Manual white balance. In this mode the white balance should be set with setColorTemperature() |
QCamera::WhiteBalanceSunlight | 2 | Sunlight white balance mode. |
QCamera::WhiteBalanceCloudy | 3 | Cloudy white balance mode. |
QCamera::WhiteBalanceShade | 4 | Shade white balance mode. |
QCamera::WhiteBalanceTungsten | 5 | Tungsten (incandescent) white balance mode. |
QCamera::WhiteBalanceFluorescent | 6 | Fluorescent white balance mode. |
QCamera::WhiteBalanceFlash | 7 | Flash white balance mode. |
QCamera::WhiteBalanceSunset | 8 | Sunset white balance mode. |
Property Documentation
active : bool
Describes whether the camera is currently active.
Access functions:
Notifier signal:
| void | activeChanged(bool) |
cameraDevice : QCameraDevice
Returns the QCameraDevice object associated with this camera.
Access functions:
| QCameraDevice | cameraDevice() const |
| void | setCameraDevice(const QCameraDevice &cameraDevice) |
Notifier signal:
| void | cameraDeviceChanged() |
cameraFormat : QCameraFormat
Returns the camera format currently used by the camera.
Note: When using the FFMPEG backend on an Android target device if you request YUV420P format, you will receive either a fully planar 4:2:0 YUV420P or a semi-planar NV12/NV21. This depends on the codec implemented by the device OEM.
Access functions:
| QCameraFormat | cameraFormat() const |
| void | setCameraFormat(const QCameraFormat &format) |
Notifier signal:
| void | cameraFormatChanged() |
See also QCameraDevice::videoFormats.
colorTemperature : int
Returns the current color temperature if the current white balance mode is WhiteBalanceManual. For other modes the return value is undefined.
Access functions:
| int | colorTemperature() const |
| void | setColorTemperature(int colorTemperature) |
Notifier signal:
| void | colorTemperatureChanged() const |
customFocusPoint : QPointF
This property represents the position of the custom focus point, in relative frame coordinates: QPointF(0,0) points to the left top frame point, QPointF(0.5,0.5) points to the frame center.
The custom focus point property is used only in FocusPointCustom focus mode.
You can check whether custom focus points are supported by querying supportedFeatures() with the Feature.CustomFocusPoint flag.
Access functions:
| QPointF | customFocusPoint() const |
| void | setCustomFocusPoint(const QPointF &point) |
Notifier signal:
| void | customFocusPointChanged() |
[read-only] error : const Error
Returns the error state of the camera.
Access functions:
| QCamera::Error | error() const |
Notifier signal:
| void | errorChanged() |
[read-only] errorString : const QString
Returns a human readable string describing a camera's error state.
Access functions:
| QString | errorString() const |
Notifier signal:
| void | errorChanged() |
exposureCompensation : float
Exposure compensation in EV units.
Exposure compensation property allows to adjust the automatically calculated exposure.
Access functions:
| float | exposureCompensation() const |
| void | setExposureCompensation(float ev) |
Notifier signal:
| void | exposureCompensationChanged(float value) |
exposureMode : QCamera::ExposureMode
This property holds the exposure mode being used.
Access functions:
| QCamera::ExposureMode | exposureMode() const |
| void | setExposureMode(QCamera::ExposureMode mode) |
Notifier signal:
| void | exposureModeChanged() |
See also QCamera::isExposureModeSupported.
[read-only] exposureTime : const float
Camera's exposure time in seconds.
Access functions:
| float | exposureTime() const |
Notifier signal:
| void | exposureTimeChanged(float speed) |
See also minimumExposureTime(), maximumExposureTime(), and setManualExposureTime().
flashMode : QCamera::FlashMode
This property holds the flash mode being used.
Enables a certain flash mode if the camera has a flash.
Access functions:
| QCamera::FlashMode | flashMode() const |
| void | setFlashMode(QCamera::FlashMode mode) |
Notifier signal:
| void | flashModeChanged() |
See also QCamera::FlashMode, QCamera::isFlashModeSupported, and QCamera::isFlashReady.
[read-only] flashReady : const bool
Indicates if the flash is charged and ready to use.
Access functions:
| bool | isFlashReady() const | [see note below] |
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
Notifier signal:
| void | flashReady(bool ready) |
focusDistance : float
This property return an approximate focus distance of the camera. The value reported is between 0 and 1, 0 being the closest possible focus distance, 1 being as far away as possible. Note that 1 is often, but not always infinity.
Setting the focus distance will be ignored unless the focus mode is set to FocusModeManual.
Access functions:
| float | focusDistance() const |
| void | setFocusDistance(float d) |
Notifier signal:
| void | focusDistanceChanged(float) |
focusMode : FocusMode
This property holds the current camera focus mode.
Sets up different focus modes for the camera. All auto focus modes will focus continuously. Locking the focus is possible by setting the focus mode to FocusModeManual. This will keep the current focus and stop any automatic focusing.
Access functions:
| QCamera::FocusMode | focusMode() const |
| void | setFocusMode(QCamera::FocusMode mode) |
Notifier signal:
| void | focusModeChanged() |
See also isFocusModeSupported.
[read-only] focusPoint : const QPointF
Returns the point currently used by the auto focus system to focus onto.
Access functions:
| QPointF | focusPoint() const |
Notifier signal:
| void | focusPointChanged() |
[read-only] isoSensitivity : const int
This property holds the sensor ISO sensitivity.
Describes the ISO sensitivity currently used by the camera.
Access functions:
| int | isoSensitivity() const |
Notifier signal:
| void | isoSensitivityChanged(int value) |
See also setAutoIsoSensitivity() and setManualIsoSensitivity().
manualExposureTime : int
Set the manual exposure time to seconds
Access functions:
| float | manualExposureTime() const |
| void | setManualExposureTime(float seconds) |
Notifier signal:
| void | manualExposureTimeChanged(float speed) |
manualIsoSensitivity : int
Describes a manually set ISO sensitivity
Setting this property to -1 (the default), implies that the camera automatically adjusts the ISO sensitivity.
Access functions:
| int | manualIsoSensitivity() const |
| void | setManualIsoSensitivity(int iso) |
Notifier signal:
| void | manualIsoSensitivityChanged(int) |
[read-only] maximumZoomFactor : const float
Returns the maximum zoom factor.
This will be 1.0 on cameras that do not support zooming.
Access functions:
| float | maximumZoomFactor() const |
Notifier signal:
| void | maximumZoomFactorChanged(float) |
[read-only] minimumZoomFactor : const float
Returns the minimum zoom factor.
This will be 1.0 on cameras that do not support zooming.
Access functions:
| float | minimumZoomFactor() const |
Notifier signal:
| void | minimumZoomFactorChanged(float) |
[read-only] supportedFeatures : const Features
Returns the features supported by this camera.
Access functions:
| QCamera::Features | supportedFeatures() const |
Notifier signal:
| void | supportedFeaturesChanged() |
See also QCamera::Feature.
torchMode : QCamera::TorchMode
This property holds the torch mode being used.
A torch is a continuous source of light. It can be used during video recording in low light conditions. Enabling torch mode will usually override any currently set flash mode.
Access functions:
| QCamera::TorchMode | torchMode() const |
| void | setTorchMode(QCamera::TorchMode mode) |
Notifier signal:
| void | torchModeChanged() |
See also QCamera::TorchMode, QCamera::isTorchModeSupported, and QCamera::flashMode.
whiteBalanceMode : WhiteBalanceMode
Returns the white balance mode being used.
Access functions:
| QCamera::WhiteBalanceMode | whiteBalanceMode() const |
| void | setWhiteBalanceMode(QCamera::WhiteBalanceMode mode) |
Notifier signal:
| void | whiteBalanceModeChanged() const |
zoomFactor : float
This property holds the current zoom factor.
Gets or sets the current zoom factor. Values will be clamped between minimumZoomFactor and maximumZoomFactor.
Access functions:
| float | zoomFactor() const |
| void | setZoomFactor(float factor) |
Notifier signal:
| void | zoomFactorChanged(float) |
Member Function Documentation
[explicit] QCamera::QCamera(QObject *parent = nullptr)
Construct a QCamera with a parent.
Selects the default camera on the system if more than one camera is available.
[explicit] QCamera::QCamera(const QCameraDevice &cameraDevice, QObject *parent = nullptr)
Construct a QCamera from a camera description cameraDevice and parent.
[explicit] QCamera::QCamera(QCameraDevice::Position position, QObject *parent = nullptr)
Construct a QCamera which uses a hardware camera located a the specified position.
For example on a mobile phone it can be used to easily choose between front-facing and back-facing cameras.
If no camera is available at the specified position or if position is QCameraDevice::UnspecifiedPosition, the default camera is used.
[virtual noexcept] QCamera::~QCamera()
Destroys the camera object.
QMediaCaptureSession *QCamera::captureSession() const
Returns the capture session this camera is connected to, or a nullptr if the camera is not connected to a capture session.
use QMediaCaptureSession::setCamera() to connect the camera to a session.
[signal] void QCamera::errorOccurred(QCamera::Error error, const QString &errorString)
This signal is emitted when error state changes to error. A description of the error is provided as errorString.
[signal] void QCamera::exposureCompensationChanged(float value)
Signal emitted when the exposure compensation changes to value.
Note: Notifier signal for property exposureCompensation.
float QCamera::exposureTime() const
Returns the current exposure time in seconds.
Note: Getter function for property exposureTime.
[signal] void QCamera::exposureTimeChanged(float speed)
Signals that a camera's exposure speed has changed.
Note: Notifier signal for property exposureTime.
[signal] void QCamera::flashReady(bool ready)
Signal the flash ready status has changed.
Note: Notifier signal for property flashReady.
[signal] void QCamera::focusModeChanged()
Signals when the focusMode changes.
Note: Notifier signal for property focusMode.
bool QCamera::isActive() const
Returns true if the camera is currently active.
Note: Getter function for property active.
bool QCamera::isAvailable() const
Returns true if the camera can be used.
[invokable] bool QCamera::isExposureModeSupported(QCamera::ExposureMode mode) const
Returns true if the exposure mode is supported.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
[invokable] bool QCamera::isFlashModeSupported(QCamera::FlashMode mode) const
Returns true if the flash mode is supported.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
[invokable] bool QCamera::isFlashReady() const
Returns true if flash is charged.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
Note: Getter function for property flashReady.
[invokable] bool QCamera::isFocusModeSupported(QCamera::FocusMode mode) const
Returns true if the focus mode is supported by the camera.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
[invokable] bool QCamera::isTorchModeSupported(QCamera::TorchMode mode) const
Returns true if the torch mode is supported.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
[invokable] bool QCamera::isWhiteBalanceModeSupported(QCamera::WhiteBalanceMode mode) const
Returns true if the white balance mode is supported.
Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.
[signal] void QCamera::isoSensitivityChanged(int value)
Signal emitted when sensitivity changes to value.
Note: Notifier signal for property isoSensitivity.
float QCamera::manualExposureTime() const
Returns the manual exposure time in seconds, or -1 if the camera is using automatic exposure times.
Note: Getter function for property manualExposureTime.
See also setManualExposureTime().
float QCamera::maximumExposureTime() const
The maximal exposure time in seconds.
int QCamera::maximumIsoSensitivity() const
Returns the maximum ISO sensitivity supported by the camera.
float QCamera::minimumExposureTime() const
The minimal exposure time in seconds.
int QCamera::minimumIsoSensitivity() const
Returns the minimum ISO sensitivity supported by the camera.
[slot] void QCamera::setActive(bool active)
Turns the camera on if active is true, or off if it's false.
Note: Setter function for property active.
See also isActive().
[slot] void QCamera::setAutoExposureTime()
Use automatically calculated exposure time
[slot] void QCamera::setAutoIsoSensitivity()
Turn on auto sensitivity
void QCamera::setCameraDevice(const QCameraDevice &cameraDevice)
Connects the camera object to the physical camera device described by cameraDevice. Using a default constructed QCameraDevice object as cameraDevice will connect the camera to the system default camera device.
Note: Setter function for property cameraDevice.
See also cameraDevice().
void QCamera::setCameraFormat(const QCameraFormat &format)
Tells the camera to use the format described by format. This can be used to define a specific resolution and frame rate to be used for recording and image capture.
Note: When using the FFMPEG backend on an Android target device if you request YUV420P format, you will receive either a fully planar 4:2:0 YUV420P or a semi-planar NV12/NV21. This depends on the codec implemented by the device OEM.
Note: Setter function for property cameraFormat.
See also cameraFormat().
[slot] void QCamera::setColorTemperature(int colorTemperature)
Sets manual white balance to colorTemperature. This is used when whiteBalanceMode() is set to WhiteBalanceManual. The units are Kelvin.
Setting a color temperature will only have an effect if WhiteBalanceManual is supported. In this case, setting a temperature greater 0 will automatically set the white balance mode to WhiteBalanceManual. Setting the temperature to 0 will reset the white balance mode to WhiteBalanceAuto.
Note: Setter function for property colorTemperature.
See also colorTemperature().
[slot] void QCamera::setWhiteBalanceMode(QCamera::WhiteBalanceMode mode)
Sets the white balance to mode.
Note: Setter function for property whiteBalanceMode.
See also whiteBalanceMode().
void QCamera::setZoomFactor(float factor)
Zooms to a zoom factor factor at a rate of 1 factor per second.
Note: Setter function for property zoomFactor.
See also zoomFactor().
[slot] void QCamera::start()
Starts the camera.
Same as setActive(true).
If the camera can't be started for some reason, the errorOccurred() signal is emitted.
[slot] void QCamera::stop()
Stops the camera. Same as setActive(false).
[slot] void QCamera::zoomTo(float factor, float rate)
Zooms to a zoom factor factor using rate.
The rate is specified in powers of two per second. At a rate of 1 it would take 2 seconds to go from a zoom factor of 1 to 4.
Note: Using a specific rate is not supported on all cameras. If not supported, zooming will happen as fast as possible.