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DNG, Lightroom and getting in the RAW

Embracing 16-bit imaging and the digital negative By Mike Jones

Technology is an ongoing evolution of consistent refinement and (arguably, more often than not) improvement. However, the graph line of this evolution is far from a linear progression of equal and incremental steps. Not all technological shifts are created equal and the graph is pock marked with accelerated peaks; those changes that represent paradigm shifts in technical production.

In the context of digital imaging, aside from the shift from film to digital itself, no change has been more profound than RAW format and the Digital Negative. Image file formats have come and gone and found their particular niche of most appropriate usage - TIFFs for printing reproduction, JPEGs for compressed delivery, GIF and PNG for websites and so on. But the common trait that unites all these traditional formats is exactly the trait lacking from the RAW format: Processing.

When a digital photograph is taken, not only is the light via the lens captured to form an image but the data acquired on the image sensor is processed with a vast array of information based on the settings selected on the camera itself. White balance, exposure and the color profile of the camera are all applied after the image is initially captured and then processed and compressed into the image data to produce a final processed image. The inherent downside of in-camera processing is two-fold; first, a great deal of source image information is discarded in the processing and second, image properties such as white balance and color profile are fixed in the image and cannot be changed later.

Lightroom Auto DNG import

The RAW format dispenses with both these problems. Cameras that shoot RAW format images literally capture the raw image data directly off the sensor without processing it. Parameters such as White balance are recorded as metadata information inside the file but not actually applied to the image information; there is no processing inside the camera. This allows for these parameters to be freely altered and modified after the image has been taken.


Anyone familiar with traditional darkroom processing of film negatives will see some similarity here whereby the contrast and tone of a photo is produced in large part after the image is taken by its exposure and processing in the darkroom.

The other major element of the RAW format is the bit depth of the image. Traditional JPEG and TIFF files use an 8-bit color space 8 bits of data for each RGB color channel for each pixel. The image sensor in the camera however, captures a greater bit depth than this (generally 12, 14 or even 16 bits) and the RAW format preserves this data rather than being disposed of in the processing to JPEG or TIFF. The result is a RAW file created in up to 16-bit color space; 16 bits of information per pixel, per color channel. This jump from 8 to 16 bits is a whole lot more than double; to put it in pure numeric terms an 8-bit image is capable of 256 levels of brightness from black to white. A 16-bit image by vast contrast has 4096 levels of brightness. An 8-bit image can produce 16.7 million colors a 16-bit image has 281 trillion!

So right from the outset a RAW image has a massively larger body of visual information that can be drawn upon in post photo processing. Of course the catch is that a RAW file demands post-processing to be useful. A RAW photo straight from the camera is far from aesthetically pleasing as the lack of processing means the photo looks really quite dull and lifeless. What's required to take advantage of that extra information is a software imaging application for processing RAW data to sculpt a great image from that vast amount of raw clay.

While the ubiquitous Photoshop has had dedicated tools for RAW image processing for some time the take up of RAW has lead to a new breed of imaging tools dedicated to RAW processing and image management; a charge lead by Adobe's Lightroom.There however has been an inherent problem with RAW format images; the age old problem that has beset so many production formats. There is no unified RAW format standard. Whilst the concept is the same for all developers the implementation varies enormously from camera brand to brand with little to no compatibility between.

To deal with this most camera makers using RAW have developed their own RAW processing software that deals with their particular flavor of RAW. But lets face it, software made by a camera company whose area of expertise is not in software design more often than not results in software that is pretty clumsy and under-developed.


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