RAW : The Digital Negative

The RAW is the only file format that allows to fulfill the potential of the camera; it is a kind of "digital negative", since is provides an unprocessed image that must be optimized with an image editor before being printed or published on internet.

The Characteristics of RAW

One name, many formats : nowadays, there are more than twenty RAW formats, since every manufacturer uses a proprietary RAW format: for example, the Canon's RAW is .crw ; Nikon's RAW is .nef ; Olympus's RAW is .orf , etc.
On september 27, 2004, Adobe announced the DNG, an open RAW format that may become the standard in next years. Currently, there are three manufacturers that use DNG as RAW format: Leica, Ricoh and Hasselblad.

Unprocessed files : the RAW files are almost unprocessed; you can change all the camera parameters (contrast, sharpening, colors space, white balance, etc.) when you open the file with your image editor. This is one of the great advantages of RAW: for example, if you accidentally apply an exaggerate in-camera sharpening to the RAW file, you can correct it. With JPEG, instead, there is not way to correct in-camera over-sharpening and other errors.

File size : RAW files are larger than JPEG, but nowadays there are cheap and very capable memory cards.

Wide bit depth : the RAW format is usually 12 bit, and sometimes even 16 bit (JPEG, instead, is 8 bit). The bit depth is an important attribute of every image format; it specifies how many bits are used to create a color, and then how many shades of color can be represented.
The bits are the basic units of the entire digital world. A computer understands just two values : 0 (off) and 1 (on); and a bit is right that : a 0 or an 1. To get more values, you have to combine more than one bit (note: a combination of bits is called byte). With two bits, you have four (2²) values : [0,0]; [0,1]; [1,0]; [1,1]. Three bits correspond to 2³ -> 8 values, 4 bits-> 16 values, etc. A commonly used bit depth is 8 bit, that has 256 values per channel. Other bit depth used in cameras and scanners are 12 bit (4096 values) and 16 bit (65536).
These values are referred to just one color channel: if you consider all three channels (red, green, blue), you have 16,8 millions of tonalities with a 8 bit image, while a 16 bit image has 281474,9 billions of tonalities! The obvious advantage of high bit depth is that you you can represent much more subtle color tonalities and you can make finer adjustments during the post processing; other than that, you need a wide bit depth to store the entire dynamic range that the camera is able to capture.
The following crops show a practical example of the advantages of high bit depth.

A	B	C

The image A is a crop taken from a very underexposed landscape photo (this is an "extreme" example, that photo was underexposed by more than 5 stops!).

The image B is the same crop, taken from a JPEG image (8 bit) and brightened up with levels to show some detail. The colors are inaccurate, and the lower portion of the frame has a very visible banding.

The image C is the crop taken from a RAW image (12 bit) and brightened up to show some detail. Thanks to the higher number of tonalities that are represented in the RAW file, there is much more detail and the colors are acceptable.

When You Should Use RAW

If you do nature photography, you should use RAW as in-camera file format. JPEG is a great format for internet uses, but it does not give the same quality of RAW. Sport photographers or photo journalist can trade some image quality for the faster workflow given by JPEG files, but for nature photographers there is not any good motive to use JPEG in-camera.

The RAW workflow is not as complex as you might thinks. You just have to convert the RAW file with a RAW converter; I recommend ACR (Adobe camera). Do not use the "Default" values suggested by the program!
Set all the sliders on the average value, with few exceptions: if the photo is very underexposed of overexposed, use the Exposure slider to give the right brightness to the photos. Always set the "Sharpness" and "Noise Reduction" sliders, included in the "Detail" tab, on 0. Finally, open the photo in 16 bit / Adobe RGB mode. 

When you have opened the 16 bit image, you can edit it how you prefer (if you want to learn the best techniques to enhance the image with Photoshop, I'd suggest to read carefully the articles of the "Post Processing" section ). When you have finished, save the photo a TIFF.

Do you have comments or questions?

If you have comments or questions about this article, feel free to ask in the Juza Nature Photography Discussion Forum!