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March 28, 2010
The extra latitude with raw images
I’ve been playing about with the Canon Hackers Development Kit (CHDK) which is free, open-source firmware for a range of Canon Point & Shoot cameras. We’ve got a cheapy A430, which out of the box takes distinctly average images. Most Point & Shoot cameras will only record JPEG images. However, this is usually just a restriction imposed by the factory firmware installed on the camera. CHDK adds so many extra features to cameras that it supports, including support for recording the raw data from the camera’s image sensor (I shoot almost exclusively raw on my DSLR). JPEGs are 8-bit image files (i.e. 8 binary bits of information per pixel). My Canon DSLR has 12 bits of information per pixel (with 12 bits, each colour channel can be between 0 & 4096 instead of between 0 & 255 for JPEG), and the newer Canon DSLRs record 14 bits of information per pixel. CHDK “only” allows our cheapy A430 to record 10 bits of info when shooting raw, but the two images shown below are a fair example of how much information the camera can actually retrieve from the sensor when it’s not being crippled by the combination of the low-end factory-installed Canon firmware and the 8-bit JPEG file format. Note the difference in both the highlights (the sky) and the shadows (garden areas), and the more accurate white balance.
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| The image processed in-camera in JPEG | The raw version processed in Adobe Lightroom and converted to JPEG. |
Posted by conor at March 28, 2010 9:32 AM