Shooting RAW

Are you one of those people who knows it is possible to shoot RAW, but has been afraid of the extra work involved? Or have you justified avoiding RAW by thinking along the lines: 'I get those fantastic JPEG images, why should I bother?' Then you should read on. There are a lot of advantages to starting work in your digital darkroom right from the development of your digital negative!

Let’s first discuss how the digital capture works, and then consider the difference in processing RAW and JPEG image files.

When the shutter is released, the digital sensor measures the amount of light that hits it and converts the signal into a digital value from 0 for pure black to (at least) 4095 for pure white. This 12-bit (or 14-bit) number distinguishes 4096 shades of gray. There is no colour information captured, just the luminance value for each pixel. The colour image is derived from the RAW file by a raw converter through a process called demosaicing . That is the very reason why most cameras are known as 'colour filter array' or 'mosaic sensor' cameras. Some cameras, like the Sigma SD series, use Foveon X3 technology, which captures colour by means of three layers of photo sensors. In either case, a lossless RAW file is produced containing all of the information available about the image taken. All hi-end digital cameras, including most point and shoot cameras, can produce RAW image files as a digital negative.

Processing JPEG image files

When the camera is set to capture JPEG images, the RAW data is converted, actually developed would be the correct operative verb here, internally by the camera. You have control over a few settings like the colour space, saturation, and white balance, though it is the camera doing the important initial development step for you. The result is a JPEG image file, which is a lossy file format. JPEG is an 8-bit format (256 shades of gray), so the image will be unable to recreate some of the tonal quality available in the original RAW data. JPEG image files are also compressed to save disk space. This destructive compression is applied when the file is initially saved in the camera.

The JPEG file is then typically loaded into an image editing software such as Adobe Photoshop . It is then adjusted using tools such as levels, and curves. These edits in Photoshop are also destructive, potentially leading to posterization and compression of tonal range. Of course, when the editing is finished, the JPEG file is again saved, losing yet more information as it is once again compressed to save disk space.

Processing RAW image files

A RAW image file captures everything the camera has to offer. It yields a 12-bit (or even 14-bit) file. The only on-camera settings that have an effect on raw data are the ISO speed, shutter speed, and aperture. One can rework the other settings such as white balance and colour space in a raw converter. Like film processing, it is possible to develop RAW images using standard settings to get a decent result, but you can also use advanced techniques and get a better file with subtle differences in contrast, hues and saturation. RAW processing also reduces the possibility of getting a poor image through incorrect technical settings such as white balance since it allows you to take full control of the processing. In fact, it is possible to produce a file that needs minimum editing in the photo editor, limiting the need to destructively process the file. Once processing is completed, the image can be saved in the TIFF or PSD formats, which are lossless.

Learning how to process a RAW digital negative has a learning curve. If this sounds like more work, it is. However, the effort is worth it. If done properly, you will spend less and less time editing images, and you will improve your overall image quality. RAW processing helps in creating a better result - a better print, which is the ultimate goal of photography.

To summarize -

When you shoot raw,

• You get a 12- or 14-bit file, compared to the 8-bit JPEG format. Thus it is possible to get at least 4,096 levels in each channel compared to 256.
• Technical mistakes, such as improper exposure error, can be better corrected later. (Of course, it is still very important to learn the exposure theory and use the Histogram.)
• Technical settings, such as colour space and white balance, are determined during the controlled conversion process.
• You control the interpretation of the image and give shape to the final outcome, including colour space and white balance, saturation and sharpness.
• The initial image file can be created with minimal loss of quality as a TIFF or PSD file.
• One can always reinterpret the digital negative later if needed!

Of course this comes at a premium,

• You need to process the file. This takes time and learning.
• File size is typically bigger after the conversion. (Though with the storage media getting cheaper everyday this is somewhat mitigated).
• Another concern is about the longevity of the format. Every camera manufacturer has its own format for raw file. However, with Photoshop’s (one of the best photo editor) .DNG format one can be sure that all the work is saved in an open and documented format.

Does this mean the JPEGs captured by the current hi-end digital cameras are no good at all? Absolutely not! For instance, if you are a sports or press photographer you need quick results. The JPEG files produced by these cameras are of very good quality and can be quickly given to the client.

However, if you are working in a variable light, like to make subtle changes to your outcome, and love the control over the workflow, RAW is for you.

I have given an example image which was made in high contrast light. The trees in the background were lit by the first light and there were subtle green-hues warmed with the early light. Some rays and reflected light were also illuminating the foreground tree-trunks. I processed the image in my raw converter to get the vision I had while viewing the scene through my viewfinder. The JPEG produced by the camera was cold and the shadows were blocked. This would need quite a bit of work to recreate the original vision, whereas the TIFF is ready to print.

About the Author

More of Prashant Khapane's work can be found on his website; Painting with Light