Testing Multiple Pi Camera Options With Python

It’s easy taking photos using the Pi camera module using the excellent raspistill command line utility or the PiCamera Python library. I wanted to experiment with the different settings available for EX (Exposure) and AWB (Auto White Balance) and see how they performed in different environments.

Trying different settings manually seemed like a lot of work so I decided to write some scripts that would take a sequence of photos using all available options. I could then quickly review the photos and see which ones looked best in a particular environment.

The scripts could be used whenever I needed to quickly check if tweaking the options was worth considering.

Option 1 : Python script using Raspistill

Raspistill is the command line utility included with Raspbian that gives you an easy way to control the Pi camera. An example command which uses the EX and AWB options is shown below :

raspistill -o myphoto.jpg -ex night -awb shade

These ex and awb options can be set to the following values :

-ex

off,auto,night,nightpreview,backlight,spotlight,sports
snow,beach,verylong,fixedfps,antishake,fireworks

-awb

off,auto,sun,cloud,shade,tungsten,fluorescent,
incandescent,flash,horizon

Here is a link to the script that uses raspistill to take the sequence of images : pi_camera_options1.py

You can download directly to your Pi using :

wget https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/camera/pi_camera_options1.py

It can be run using :

python pi_camera_options1.py

or :

python3 pi_camera_options1.py

The total number of photos required to try out all of the combinations will be over 100. I didn’t want quite this number of photos so only a selection of options are defined in the “list_ex” and “list_awb” lists. You and add other values if required.

Option 2 : Python script using PiCamera library

Rather than use the command line you can also take photos using the excellent PiCamera Python library. Here is a link to the script that uses PiCamera to take the sequence of images : pi_camera_options2.py

You can download directly to your Pi using :

wget https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/camera/pi_camera_options2.py

It can be run using :

python pi_camera_options2.py

or :

python3 pi_camera_options2.py

As with the raspistill script you can edit this example and add additional values to the “list_ex” and “list_awb” lists.

PiCamera uses the older set of AWB values. This means it uses “sunlight” and “cloudy” while Raspistill uses “sun” and “cloudy”.

The PiCamera version has the advantage that it embeds text in the photo so it is clear what settings were used to create it.

Results

The images created by either script will be saved in the same directory as the script so you may want to run them in a sub-directory to keep your test files together.

My tests were run by taking photos out my study window. I used the free image utility XnView to create a “Contact Sheet” with a set of the photos :

As you can see there is big difference between the images. In this case one of the better images is the Automatic setting (top left) but the clouds are slightly clearer where EX was “auto” and AWB was “horizon”. I suspect “horizon” is better for images where the top half of the scene is brighter than the lower half.

Funnily enough the “cloud” setting (below left) didn’t do as good a job on the clouds compared to the “horizon” setting (below right).

In this example the default settings were great. These scripts will prove more useful when you are dealing with a more challenging scene, perhaps with lower light levels, nature photography or stop motion animation.