Digital Photography Live

What is a RAW file?

It is often a hot topic for discussion whether to shoot RAW or JPEG. Professional photographers looking to do a bit of post production of their photographs before submitting for publishing prefer shooting their pictures in RAW. Again, sports photographers and photojournalists covering other interest areas may not have that luxury to do post processing because of the limited time frame within which they have to submit their photographs. They prefer to simply shoot large fine JPEGS. So, what is RAW and why the photography world is divided into two over RAW?

RAW is the unprocessed file format that the camera shoots which has approximately 12 to 14 bits of data and allows you a corresponding amount of brightness levels to start with during post processing. This again is directly related to what camera you use. Most DSLRs can shoot between 12 to 14 bits. There are some point and shoots which also offers the option to shoot RAW. However it is very rarely that a camera can shoot at 16 bits. Explaining this in other words, RAW is the same image that the sensor of the camera sees using the three primary colors of red, blue and green which has not been processed yet. It can be compared to a film of negatives that has not been developed.

The sensor plate of the camera has tiny pixels which are sensitive to light and capture photons. If we compare the sensor plate of the camera to individual cameras, then each single pixel can record only one of the three primary colors of red, green and blue. The reason is if they are made to collect all the primary colors then it will be impossible to determine how much of each has been accumulated by the pixels. A filter is placed over these sensors to ensure that they can record only one of the colors and reflect back the rest. Once the exposure is completed the photons collected by the pixels are then analyzed and then processed by the camera’s image processing system.

There are different types of filter arrangements used in digital cameras to collect the image information. The most common being the Bayer array or combination of filters. It has an arrangement of rows of filters representing the three primary colors. If we can magnify the filter array we will notice that the green filters outnumber the red and blue. There is a reason for this of course. The human eye is more susceptible to the green color.

Once the exposure is made and if the camera is set to record images in JPEGs the image processing system kicks in and does the post processing in-camera. However there is a definite drawback to that as most of the modern digital cameras do not have the processing power that is necessary to process RAW images correctly. Professional photographers and those who are looking for more accuracy in the process of demosaicing prefer to do their post processing on computers which are faster and have more processing speeds leading to a more accurate depiction of the actual scene.