The RAW vs JPEG
Jpeg vs RAW files, 2 Stops Overexposed
RAW files have a clear advantage over JPEG files for a variety of reasons, one of them being the exposure advantage. Each digital camera has a certain amount of exposure latitude. Exposure latitude is how much you can be over or under the optimum (ideal) exposure, and still end up with a great photo (after correcting the over or underexposure in your favorite image editing software). You will have a lot more exposure latitude with RAW files than with JPEG files.
You can check this out for yourself by doing a simple exposure test.
Pick a scene with a wide range of tones from white to black. Set your camera to capture RAW + JPEG files. Use an 18% gray card to determine your initial exposure. Then take additional exposures in one stop increments from 3 stops over exposed to 6 stops underexposed. You will end up with a series of photos looking something like the series of photos on this page.
Open each file and correct the over or underexposure with your favorite image editing software. When you are done, compare your photos. Some will look awful, even after trying to correct them. Some will look ok and some will look great. It will be obvious that your RAW files have more exposure latitude than the JPEGs.
Original Jpeg file, 2 stops overexposed, uncorrected
Let's look at one pair of photos from my exposure latitude test. The examples on this page are RAW and JPEG files, captured at the same time at 2 stops over the optimum (best) exposure. In the JPEG photo immediately above, the highlights on the white house and clouds are totally blown out (washed out and texture less), and the blue sky has lost the richness of the colors.
JPEG file, 2 stops overexposed, corrected in Photoshop
An attempt to correct the JPEG file (above) isn't very successful. The washed out highlights are still gone and can't be recovered. Most of the blue sky lacks any attractive color tones. Although it is hard to see in this small web sized file, an attempt to bring back the blue color in the sky with Adobe Photoshop (using levels, curves, and hue saturation) is already resulting in color banding and pixelization in the lighter areas of the sky. The JPEG file just doesn't have enough information to make recovery possible, even after several minutes of intensive work.
Color banding and pixelization in the blue sky
I took the saturation of the blue sky one step farther to make the banding and pixelization more obvious in a web sized file. A cropped portion of the sky is shown above.
The story with the RAW file at the same exposure is entirely different. I opened the RAW file in Adobe Camera Raw, moved a few sliders to recover most of the color in the photo, and in less than 30 seconds, I had the photo below.
RAW file, 2 stops overexposed
corrected with Adobe camera raw
As you can see, the white house is looking much better, The blue sky is far superior to the JPEG photo. I could have increased the saturation even more to jazz up the colors without any risk of color banding or pixelization.
With the same amount of over exposure, the RAW file gives me a good photo with less than 30 seconds work. The JPEG file is unacceptable with poor color, completely washed out highlights, and the beginnings of color banding and pixelization, even after several minutes work.
Of course, it is wise to get the best possible exposure to begin with. But in the real world under occasionally hectic conditions, even the best of photographers can miss the ideal exposure. Even with the ideal exposure, RAW files give you more room to work with the image in post processing.
Why is a RAW file so much better? When the camera creates a JPEG file, it takes the 12-bit or 14-bit raw image information from the digital sensor and creates an almost instantaneous, 8-bit JPEG file, but it throws away most of the originally captured image information. A raw file keeps most of the originally captured image information. JPEG files can be remarkably good, but a RAW file gives you a lot more when you need that extra information. It's like the difference between a box of 64 crayons versus a box of 8.
An 8-bit JPEG file, in black and white terms, has 256 tonality gradations (shades of gray) from jet black to pure white. A 12-bit RAW files has 4096 tonality shades, and a 14-bit RAW files has 16,384 tonality shades. RAW files have a lot more image information for your software to work with.
Set your camera to RAW + JPEG. If you miss an exposure, the RAW file will give you a lot more exposure latitude in recovering the image. It can make the difference between a good photo and a throwaway. Even with the right exposure, the RAW file gives you more room to play with color and contrast via levels, curves and hue saturation in your favorite image editing software.
The most detailed information about metering, camera meters, and other metering tools is in my book, Digital Photography Exposure for Dummies.
Copyright © Jim Doty, Jr. All rights reserved.