Exposure series iterate through a specified range of an exposure parameter, keeping all other exposure parameters constant.
In general, exposure is controlled by three parameters: aperture, exposure time and ISO value.
Raspberry Pi cameras have a fixed or manually controlled aperture and ISO values are not standardized.
Instead of ISO values, the Analogue gaing can be set. Roughly, the relation is ISO = 100 * AnalogueGain.
The Exposure Series subdialog allows specifying necessary parameters for series where either Exposure Time or Analogue Gain is varied.
The dialog references the active Photo Series which is managed in the Series subdialog of the Photo Series dialog.
The Number of Shots is shown here, because it will be affected by the chosen Start, Stop and Interval values.
To configure the active Photo Series as Exposure Series, proceed as follows
- Activate the Exposure Series checkbox
- Select the exposure parameter which shall be kept at a fixed value by checking one of the check boxes under Exposure Time or Analogue Gain
- For the selected parameter, enter the intended value in the Start field.
- Now, specify Start and Stop values for the variable parameter
- The interval is specified in terms of photographic Exposure Values (EV)
With a value of 1/3 EV the series is obtained by multiplying the last value of Exposure Time or Analogue Gain by 2**(1/3) to get the next value.
With a value of 1 EV, the factor is 2**(1)=2
and with 2 EV, the factor is 2**(2)=4.
1/3 EV is the typical raster value for commercial cameras when modifying either aperture, exposure time or ISO.
Finally push the Submit button to store the specified value.
This will recalculate the Number of Shots required for the series.
To start photoshooting, go to the Series subdialog
After the series has finished, the results can be inspected on the Exposure Series subscreen:
Together with each photo, the screen shows a histogram and characteristic metadata:
- Exp: Exposure Time in seconds
- Gain: Analogue Gain
- Lux: An estimation of the brightness
More information can be gained from
- the Series Camera File which lists the configuration and control parameters applied before shooting a photo
- the Series Log File which lists the metadata captured together with each photo.
The following table contains systematic values for Exposure Time and Analogue Gain with 1/3 EV, corresponding roughly to commercial camera settings
The following table contains systematic values for Exposure Time and Analogue Gain with 1 EV, corresponding roughly to commercial camera settings
