RAW FILE FORMAT

What is RAW Mode?

 RAW is a general term for a variety of proprietary file formats such as Nikon’s. NEF, Canon’s. CRW and .CR2, and Olympus’. ORF. While there are many different encoding strategies, in each case the file records the raw, unprocessed image-sensor data. RAW files consist of the image pixels themselves and the image metadata, which contains a variety of information about how the image was recorded. This is needed by RAW converters in order to process the RAW capture into an RGB image.

RAW File Converters

 Because they include some additional metadata, RAW format image files must be converted by a RAW image converter before they can be utilized. These converters process the white balance, colorimetric data (the assigning of red, green, and blue to each pixel), Gamma correction, noise reduction, antialiasing (to avoid color artifacts), and sharpening. However, different converters use different algorithms; some process the tones with less contrast in order to provide editing maneuverability, others will increase the contrast of the file to achieve a more film-like rendition, for example. As a result, the same image may look different when processed by different RAW converter engines.

 How JPEG Differs from RAW

 When you shoot JPEG, a built-in RAW converter in the camera carries out all of the same tasks as described above to turn the RAW capture into a color image, then compresses it using JPEG compression. Some camera systems allow you to set parameters for this JPEG conversion— usually, a choice of sRGB or Adobe RGB 1998 color space, a sharpness setting, and a curve or contrast setting. JPEG. JPEGs offer fairly limited editing ability, since the mode applies heavy compression to the color data. In the typical conversion process, the JPEG compression will discard roughly a stop of usable dynamic range, and you have very little control over what information gets discarded.

So why do many photographers still choose to shoot JPEGs? First, shooting in JPEG mode creates smaller files, so you can save more images per CF card or storage device. Second, compared to shooting RAW files, JPEGs do not take nearly as long to write to memory. Both factors allow you to work much faster—a clear advantage in some situations. If you shoot JPEGs, selecting the JPEG Fine mode (sometimes called JPEG Highest Quality) will apply the least compression and, therefore, produce the best possible files. JPEG is a “loss” format, meaning that images are subject to degradation by repeated opening and closing of the file. Therefore, most photographers who shoot in JPEG mode save the file as a JPEG copy each time they work on it or save it to the TIFF format. TIFF is a “lossless” format, meaning that images can be saved again and again without further degradation. RAW. When you shoot in RAW mode, you get unparalleled control over the interpretation of the image. The only in-camera settings that have an effect on the captured pixels are ISO speed, shutter speed, and aperture setting. Everything else is under your control when you convert the RAW file—you can reinterpret the white balance, the colorimetric rendering, the tonal response, and the detail rendition (sharpening and noise reduction) with complete flexibility. Within limits (which vary from one RAW converter to another), you can even reinterpret the exposure compensation. While RAW files offer the benefit of retaining the highest amount of image data from the original capture, they also take longer to write to the storage media and drastically reduce the number of files you can capture

on a single CF card or micro drive because of their increased file size. Although the cost of media is coming down, the time it takes to record the information is not necessarily getting much faster. If the kind of shooting you do require fast burst rates and lots of image files— exactly what wedding photographers experience—then RAW capture may not be your best choice.