Basics - Why should you use the RAW format for photo editing

I know that most of you already know why RAW is more suitable than JPG for photo retouching. However I often need to answer that question by e-mail, so … it will be the first article thus I won’t ever repeat it .

First of all you need to know that using RAW is some sort of “perfectionist philosophy” for those, including me, who don’t tolerate the idea that the post-processing of a picture could be done by an automatic process of the camera’s body . I am one of those passionate photographers who can sometimes spent hours in the digital darkroom that is photoshop.

With current digital SLR cameras :

• JPG pictures are created from RAW. The picture is temporary saved, then it is post-processed using optimization settings of the camera’s body and finally it is compressed and stored in JPG which is a 8 bits format. A 8 bits format means that each channel Red, Green and Blue can have 256 values, so a pixel can have about 16 millions possible colors.
• RAW is a image format that only designates raw datas from the sensor, image optimization settings from the camera’s body have no impact, the picture is directly saved in the manufacturer’s proprietary raw format (NEF for Nikon, CR2 for Canon, etc.) most of the time in a 12bits definition (it can be more). A 12 bits format means that each channel Red, Green and Blue can have 4096 values, so a pixel can have about 68 billions possible colors.

All that stays very theoretical of course, shooting in raw won’t provide you 4096 times more details, however the picture is richer and it reacts better for example when enlightening dark areas.

Using RAW, for me, is like if I said to my camera “don’t touch the picture, let me do the postprocessing myself!”.

Let see that with a concreet example:

I took 2 pictures of the same place with my tripod at 100 iso, the first one in JPG max quality, the second one in RAW. I intentionally underexposed the scene to obtain a very dark area on the bed, the red outlined area will be perfect for the example.

• Step 1 : no noticeable quality difference except the JPG was postprocessed by the camera’s body (D200) according to image optimization settings and the RAW was exported under Photoshop using a raw converter (Lightroom) with default settings, so we can only see some contrast and saturation differences.
• Step 2 : Suppose I want to enlighten the dark area, so I add a level adjustment layer and I increase the luminosity modifying levels on the three channels.
• Step 3 : Do I need to go further in the demonstration ? For sure, the area is very underexposed, so there is a lack of details and the noise appears but we can clearly see the difference between the enhanced JPG and the enhanced RAW.

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This entry was posted on July 23, 2007 and is filed under Digital Photography Postprocessing. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.