Auto Algorithm Control
Auto Exposure (AE)
Auto exposure (AE) control is designed to automatically determine the exposure time and gain of the camera so that the resulting image looks as bright as expected. In general, the camera supports various auto exposure features, and these features produce different results in the final image. In addition, the camera allows users to control how fast the exposure and gain get settled.
Note that for AE to work, Exposure Auto and/or Gain Auto must be set to Once or Continuous and ISP must be enabled.
Auto Exposure Features
To enable AE, Exposure Auto and/or Gain Auto must be set to Once or Continuous. AE automatically determines the exposure time and/or gain according to the target image average.
The target image average can be manually or automatically controlled.
For manual control, set Target Grey Value Auto to Continuous and then set the desired image average in Target Grey Value. This value is a percentage of the maximum pixel value.
For automatic control, set Target Grey Value Auto to Off. The target image average is then automatically determined according to user-defined AE modes and other AE features.
By default, AE uses an exposure range of 100 to 15000 µs and/or gain range of 0 to 18 dB and target grey value, but these can be limited.
Exposure Time Lower Limit / Exposure Time Upper Limit - the lower and upper values in microseconds (µs) that the exposure time may reach when exposure is set to Once or Continuous.
Gain Lower Limit / Gain Upper Limit - the lower and upper values in decibels (dB) that the gain may reach when gain is set to Once or Continuous.
Target Grey Value Lower Limit / Target Grey Value Upper Limit - the lower and upper values in percent (%) that the target image average may reach.
Auto Exposure Damping controls how fast the exposure and gain get settled. A small damping value may result in the system being unstable. The range is from 0.0 - 1.0. The default value is 0.5.
If both exposure time and gain are set to Once or Coninuous AE determines which to adjust first by the Auto Exposure Control Priority.
If gain priority is selected, the camera sets the gain to 0 dB, and the exposure is adjusted according to the target grey level. If the maximum exposure is reached before the target grey level is hit, the gain starts to change to meet the target. This mode is used to have the minimum noise.
If exposure priority is selected, the camera sets the exposure to a small value (default is 5 ms). The gain is adjusted according to the target grey level. If maximum gain is reached before the target grey level is hit, the exposure starts to change to meet the target. This mode is used to capture fast motion.
AE Lighting Mode can compensate for strong light sources in front or behind an object. The options are: Backlight, Frontlight, or Normal. The default lighting mode is Normal. Use the Lighting Mode feature to select depending on your conditions.
Backlight Compensation
The backlight compensation mode isused when a strong light is coming from the back of the object. For example, people standing in the shade with the bright sky at the back. A regular auto exposure algorithmmakes the object underexposed in such lighting conditions. Backlight compensation is able to properly expose the object when a strong backlight occurs, regardless of the locations of the object relative to the frame.
Frontlight Compensation
The frontlight compensation mode is used when a strong light is shining in the front of the object while the background is dark. For example, a parking spot that has lights on at night while its surrounding areas are very dark. A regular auto exposure algorithm makes the object overexposed in such lighting conditions. Frontlight compensation is able to properly expose the object when a strong front light and a dark background appear, regardless of the locations of the object relative to the frame.
Auto White Balance - Color Models
When White Balance Auto is set to Continuous or Once the camera automatically adjusts the values of Balance Ratio Red and Blue to achieve good color balance. It is used to compensate for color shifts in the image caused by different lighting conditions.
There are two profiles of auto white balance: Indoor and Outdoor. These are selected with White Balance Auto Profile.
In the Outdoor profile, the values of the red and blue balance ratios are restricted to a set of expected values for normal outdoor lighting conditions (i.e., daylight).
In the Indoor profile, the values of the red and blue balance ratios can take any values within specified limits. This allows auto white balance to compensate for artificial lighting such as fluorescent lights that are more greenish than daylight. The Indoor profile can also be used for outdoor conditions, since it does not place restrictions on the white balance solution.
By default, auto white balance uses the full range of balance ratios, but these can be limited.
- White Balance Auto Lower Limit / White Balance Auto Upper Limit - the lower and upper values that auto white balance can set for the red and blue balance ratios.
White Balance Auto Damping controls the speed at which auto white balance adjusts the values of the red and blue balance ratios. The range is from 0 to 1. Higher values of damping result in the white balance changing more gradually.
By default auto white balance examines all of the pixels in the image, but it can also use a region of interest (ROI). A common use for an auto white balance ROI is placing a white object in the image and then specifying the ROI on that object. To use ROI:
- Set the ROI Selector to Auto White Balance.
- Turn on ROI Enable.
- Set the horizontal and vertical offsets (relative to the ROI being captured) with ROI Offset X and ROI Offset Y.
- Set the width and height with ROI Width and ROI Height.
Summary Table
| Name | Interface | Access | Visibility | Description |
|---|---|---|---|---|
| Target Grey Value Auto | IEnumeration | Beginner | This indicates whether the target image grey level is automatically set by the camera or manually set by the user. Note that the target grey level is in the linear domain before gamma correction is applied. | |
| Target Grey Value | IFloat | RW | This is the user-specified target grey level (image mean) to apply to the current image. Note that the target grey level is in the linear domain before gamma correction is applied. | |
| Lighting Mode | IEnumeration | RW | Beginner | Selects a lighting mode: Backlight, Frontlight or Normal (default). a. Backlight compensation: used when a strong light is coming from the back of the object. b. Frontlight compensation: used when a strong light is shining in the front of the object while the background is dark. c. Normal lighting: used when the object is not under backlight or frontlight conditions. When normal lighting is selected, metering modes are available. |
| Exposure Time Lower Limit | IFloat | RW | The smallest exposure time that auto exposure can set. | |
| Exposure Time Upper Limit | IFloat | RW | The largest exposure time that auto exposure can set. | |
| Gain Lower Limit | IFloat | RW | The smallest gain that auto exposure can set. | |
| Gain Upper Limit | IFloat | RW | The largest gain that auto exposure can set. | |
| Target Grey Value Lower Limit | IFloat | RW | The lowest value in percentage that the target mean may reach. | |
| Target Grey Value Upper Limit | IFloat | RW | The highest value in percentage that the target mean may reach. | |
| Auto Exposure Damping | IFloat | RW | Beginner | It controls how fast the exposure and gain get settled. If the value is too small, it may cause the system to be unstable. Range is from 0.0 to 1.0. Default = 0.2. |
| Auto Exposure Control Priority | IEnumeration | RW | Beginner | Selects whether to adjust gain or exposure first. When gain priority is selected, the camera fixes the gain to 0 dB, and the exposure is adjusted according to the target grey level. If the maximum exposure is reached before the target grey level is hit, the gain starts to change to meet the target. This mode is used to have the minimum noise. When exposure priority is selected, the camera sets the exposure to a small value (default is 5 ms). The gain is adjusted according to the target grey level. If maximum gain is reached before the target grey level is hit, the exposure starts to change to meet the target. This mode is used to capture fast motion. |
| White Balance Auto Lower Limit | IFloat | Expert | Controls the minimum value Auto White Balance can set for the Red/Blue BalanceRatio. | |
| White Balance Auto Upper Limit | IFloat | Expert | Controls the maximum value Auto White Balance can set the Red/Blue BalanceRatio. |
Auto Algorithm Control Features
Target Grey Value Auto
This indicates whether the target image grey level is automatically set by the camera or manually set by the user. Note that the target grey level is in the linear domain before gamma correction is applied.
| Property | Value |
|---|---|
| Name | AutoExposureTargetGreyValueAuto |
| Interface | IEnumeration |
| Access | |
| Visibility | Beginner |
| Enumeration Values |
|---|
| Off |
| Continuous |
Target Grey Value
This is the user-specified target grey level (image mean) to apply to the current image. Note that the target grey level is in the linear domain before gamma correction is applied.
| Property | Value |
|---|---|
| Name | AutoExposureTargetGreyValue |
| Interface | IFloat |
| Access | RW |
| Unit | % |
| Visibility |
Lighting Mode
Selects a lighting mode: Backlight, Frontlight or Normal (default). a. Backlight compensation: used when a strong light is coming from the back of the object. b. Frontlight compensation: used when a strong light is shining in the front of the object while the background is dark. c. Normal lighting: used when the object is not under backlight or frontlight conditions. When normal lighting is selected, metering modes are available.
| Property | Value |
|---|---|
| Name | AutoExposureLightingMode |
| Interface | IEnumeration |
| Access | RW |
| Visibility | Beginner |
| Enumeration Values |
|---|
| Backlight |
| Frontlight |
| Normal |
Exposure Time Lower Limit
The smallest exposure time that auto exposure can set.
| Property | Value |
|---|---|
| Name | AutoExposureExposureTimeLowerLimit |
| Interface | IFloat |
| Access | RW |
| Unit | us |
| Visibility |
Exposure Time Upper Limit
The largest exposure time that auto exposure can set.
| Property | Value |
|---|---|
| Name | AutoExposureExposureTimeUpperLimit |
| Interface | IFloat |
| Access | RW |
| Unit | us |
| Visibility |
Gain Lower Limit
The smallest gain that auto exposure can set.
| Property | Value |
|---|---|
| Name | AutoExposureGainLowerLimit |
| Interface | IFloat |
| Access | RW |
| Unit | dB |
| Visibility |
Gain Upper Limit
The largest gain that auto exposure can set.
| Property | Value |
|---|---|
| Name | AutoExposureGainUpperLimit |
| Interface | IFloat |
| Access | RW |
| Unit | dB |
| Visibility |
Target Grey Value Lower Limit
The lowest value in percentage that the target mean may reach.
| Property | Value |
|---|---|
| Name | AutoExposureGreyValueLowerLimit |
| Interface | IFloat |
| Access | RW |
| Unit | % |
| Visibility |
Target Grey Value Upper Limit
The highest value in percentage that the target mean may reach.
| Property | Value |
|---|---|
| Name | AutoExposureGreyValueUpperLimit |
| Interface | IFloat |
| Access | RW |
| Unit | % |
| Visibility |
Auto Exposure Damping
It controls how fast the exposure and gain get settled. If the value is too small, it may cause the system to be unstable. Range is from 0.0 to 1.0. Default = 0.2.
| Property | Value |
|---|---|
| Name | AutoExposureControlLoopDamping |
| Interface | IFloat |
| Access | RW |
| Unit | |
| Visibility | Beginner |
Auto Exposure Control Priority
Selects whether to adjust gain or exposure first. When gain priority is selected, the camera fixes the gain to 0 dB, and the exposure is adjusted according to the target grey level. If the maximum exposure is reached before the target grey level is hit, the gain starts to change to meet the target. This mode is used to have the minimum noise. When exposure priority is selected, the camera sets the exposure to a small value (default is 5 ms). The gain is adjusted according to the target grey level. If maximum gain is reached before the target grey level is hit, the exposure starts to change to meet the target. This mode is used to capture fast motion.
| Property | Value |
|---|---|
| Name | AutoExposureControlPriority |
| Interface | IEnumeration |
| Access | RW |
| Visibility | Beginner |
| Enumeration Values |
|---|
| Gain |
| ExposureTime |
White Balance Auto Lower Limit
Controls the minimum value Auto White Balance can set for the Red/Blue BalanceRatio.
| Property | Value |
|---|---|
| Name | BalanceWhiteAutoLowerLimit |
| Interface | IFloat |
| Access | |
| Unit | |
| Visibility | Expert |
White Balance Auto Upper Limit
Controls the maximum value Auto White Balance can set the Red/Blue BalanceRatio.
| Property | Value |
|---|---|
| Name | BalanceWhiteAutoUpperLimit |
| Interface | IFloat |
| Access | |
| Unit | |
| Visibility | Expert |
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