(+) Why and When You Should Shoot RAW Photos
The following is a Plus Edition article written by and copyright by Dick Eastman.
If you have a digital camera with advanced features, and if you have a photo editing program with advanced features, and if you have plenty of disk space on your hard drive, I’d suggest that you create your photos in RAW format.
What is RAW?
This is one time in technology when a 3-letter term is not an abbreviation or acronym for three words. In this case, RAW is just that: raw, unprocessed, unrefined, unchanged, original. In this case, RAW means that the image is just as the camera saw it; the picture has not yet been processed by the camera.
Most digital camera owners do not realize that, when they push the shutter, the camera takes the picture, PROCESSES IT, and then stores the processed image in the camera’s internal memory card or whatever media is used. The picture stored inside the camera is actually quite different from what the camera saw and, for simpler applications, that is a good thing.
When you push the shutter on your digital camera, a lot of things happen very quickly. The lens opens, and the image sensor is exposed to light. The image sensor is a device that converts an optical image to an electric signal. The sensor captures light and converts it into electrical signals.
The interesting thing is that the image sensor doesn’t see light in the same way that you and I do. That is, an image sensor doesn’t see bright greens as greens and pinks as pinks. In addition, the brightness may not be the same to an image sensor as it is to a human eye. A section of the photograph may seem brighter or darker to an image sensor than it does to us humans.
The default setting on most digital cameras is to send the newly-captured signal through some electronics to convert the image to something close to what the human eye sees, then save the output of that conversion process. A very complex process called demosaicing (explained at https://en.wikipedia.org/wiki/Demosaicing) first determines the color of each pixel. The resulting color image is then adjusted in various ways, including being white balanced to compensate for the type of light you were shooting in. Then the image is sharpened, compressed so that it doesn’t take up as much space, and finally stored on your memory card. Most of today’s digital cameras will store the image in JPEG (or JPG) format, which has already been compressed and (sometimes) has already lost a bit of the original sharpness.
NOTE: More expensive digital cameras typically add more options, including the ability to store photos in TIFF format, non-compressed JPEG format, or in unprocessed RAW format. Saving images in a raw format allows the user to demosaic the image(s) using software, rather than using the camera’s built-in firmware.
TIFF and non-compressed JPEG formats are great for maintaining crystal clear, uncompressed images. However, both TIFF and non-compressed JPEG pictures have already been processed to some degree by the electronics in the computer. As a result, the camera has already converted the RAW image into what the camera’s designers hope is a proper rendition of the image for the human eye. Colors have already been changed, and brightness has already been adjusted. The result most times is a close approximation of what the human eye sees. The key words in that sentence are “most times.”
In fact, no camera electronics or any other automated method of converting RAW images into TIFF or JPEG is ever perfect. As good as these conversion processes are, they are never flawless in all conditions. A picture taken in the shade may not properly convert the one bright spot in the corner. A picture of red flowers may not properly interpret the green leaves or the yellow ribbon used to tie the flowers together. Many digital cameras struggle to get white balance properly adjusted.
Again, all of this takes place inside your camera. You, as the human photographer, have no control over this conversion process UNLESS YOU SHOOT RAW.
Another issue is the number of pixels stored – in other words, the clarity. RAW files allow for much more editing than JPEG files. Your camera probably captures RAW images with 12 to 14 bits of data per pixel, but a JPEG file can only hold eight bits of data per pixel. This means that, when you shoot in JPEG mode, one of the first things your camera does is throw out a bunch of data that it captured. Most of the time, this data loss doesn’t matter as you still get an image that has the full range of tone and color that your camera can yield. But if you like to edit a lot, or if you plan on adjusting the contrast and color to extreme degrees, then this loss of data could mean trouble. RAW gives you more options.
A RAW image is just that: raw, unprocessed, unrefined, unchanged, original. In this case, RAW means that the image is just as the camera’s image sensor saw it; the picture has not been processed by the camera. If you change the settings in your camera to store pictures in RAW format, the camera bypasses the conversion process. Whatever the image sensor saw is stored directly into the memory card with no conversion whatsoever.
The problem is that the image sensor didn’t see what the human eye would have seen. The RAW image stored in the memory card will actually look much worse to the human eye than a normal processed TIFF or JPEG image. That’s where software comes in.
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