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October 04, 2006
[ SHOOTING IN THE RAW ]
DIGITAL CAMERAS DON'T REALLY TAKE COLOUR PHOTOGRAPHS. DID YOU KNOW THAT?
At the heart of a digital camera is the sensor with its array of pixels onto which the light falls. Between the sensor and the lens is a filter panel made up of microscopic red, blue and green filters. The filtered light falls onto the collector buckets on the sensor which simply counts photons, producing an electrical charge that is proportional to the amount of light falling on them. So the raw, unprocessed image that the sensor collects is in greyscale.
The in-camera processing computer turns that greyscale image into colour and saves it to the memory card, usually in a compressed form. Cameras allow the user to set the degree of compression -- referred to in the menu as Quality.
RAW (it is not an acronym but it is always written in upper case) files are saved unprocessed and uncompressed. They are typically much larger files than JPEGs. For instance, with the Pentax K100D reviewed here, the JPEG files are 2.38MB and the RAW files are 10.4MB.
RAW files must be decoded or converted into a form that can be edited and this is done with RAW converter applications. Cameras capable of RAW capture come with some sort of converter. And each camera maker has its own version of RAW. Adobe offer a free RAW converter that handles images from many different cameras and works with Photoshop.
Cameras generally do a good job of turning the photons into coloured images but in the process some of the information captured by the sensor is lost. This information carries the fine detail and nuances of tone that are on the very edge of visibility. Many photographers claim not to be able to tell the difference between high quality JPEGs and RAW images. They argue that monitors and printers can’t display this level of detail so why bother?
The advantage of RAW is not just in reproducing detail. A good RAW converter gives a high degree of post-camera control over exposure, white balance, shadow detail, brightness, contrast, saturation and sharpness -- all things that the camera calculates internally for JPEGs. It is like getting a second chance to correct mistakes made when the picture was taken.
Once the adjustments are made the image is processed, converted into another format such as TIFF or JPEG and then opened in a photo editing program.
Adobe has developed a universal RAW format called DNG. So far the only camera makers to embrace this Digital Negative format is Pentax in the forthcoming K10D and Hasselblad and Leica. Adobe argue that in a few years time there will be proprietary RAW files on discs that will not be able to be read because the software will have become obsolete. If every company standardised on DNG this would not be a problem. In the meantime Adobe offer a free converter to change Nikon, Canon, Olympus et al RAW files into DNG.
Is it worth the extra work to shoot in RAW? The dpexpert policy is that RAW is worth the trouble for our works of art -- at least we hope! -- but not worth bothering with for the informal snaps. Perfectionists of our acquaintance always shoot RAW -- we sometimes do.
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Posted by terry at October 4, 2006 07:36 AM
Worth Checking Out
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Comments
Terry,
Hassleblad and Leica are both using the DNG file type as their native raw file in the digital cameras and backs.
Posted by: Peter Williams at October 6, 2006 06:13 AM
Peter: Thanks for that information. I will change the article to include it. Terry L
Posted by: Terry at October 6, 2006 06:17 AM