Revision as of 06:47, 23 January 2012

The purpose of this project is to get HDR images using an Elphel camera.

For informations about HDR imaging see: Wikipedia.org. For informations about HDR imaging algorithms see: Debevec.org and Columbia.edu.

There are several ways how to increase the dynamic range and to achieve HDR images:

Exposure Bracketing

Autoexposure Daemon HDR Functions

The autoexposure daemon running in the camera can alternate exposure times quickly meaning recording at maximal FPS with 2 alternating exposure times is possible. This HDR-video can be record just like any other normal video with the harddisk-recorder camogm or streamed over the network.

Due to limitation how fast the exposure time change can be propagated to the image sensor HDR mode works best in Triggered mode([1]). by altering the http://*CameraIP*/tuneseq.php?mode=latency- page, setting the EXPOS value to "0". ([2]).

Manual Bracketing

You can do exposure bracketing manually with a PHP script. Just set exposure time -> capture a single frame -> change exposure time -> capture another image, etc. This will be slower than using the daemon but you have finer control over how many brackets you want and how big the EV steps between the brackets are, etc. This is best suited for still image recording where speed is not so much of an issue.

Gain Bracketing

JP4 HDR is a special raw color format that can capture a higher dynamic range in an image without introducing any artifacts as result from combining images captured at different times (exposure bracketing). Though the post processing code to develop the images is still experimental.