Image Formats: Raw vs. JPEG
The modern photographer’s dilemma: Which format should you shoot? In a nutshell, for definitive image quality, exposure control, and shadow/highlight detail, Raw is the best choice. For speed and maximum storage space, use “Fine” JPEG.
When capturing images in JPEG mode, the camera settings used to process the image, such as white balance (see “White Balance” sidebar), are permanently “baked in” at the time of capture—that is, written into the data. Some in-camera tone correction and sharpening is also applied to enhance the image. Forever after, these images cannot ever be corrected by reprocessing the image with Lightroom and/or Photoshop because of the limited depth of data captured in the JPEG format, which compresses image data.
You can adjust the level of compression for JPEG capture. Low compression ratios (higher quality) provide better overall image quality than high compressed ratios do. Higher compression saves memory space on your CF or SD card, but the downside as usual is a loss in image quality. A large (“Fine” quality) JPEG takes up about a fifth to a third as much space as an uncompressed Raw image does, with little loss in resolution or detail.
Keep in mind that many DSLRs have image sensors capable of capturing 12 to 14 bits of data per color. JPEG images are limited to storing only up to 8 bits of data per color. Typically, this means some useful shadow and highlight information is never recorded when the camera saves an image in JPEG format. The Raw format, on the other hand, stores all the information the image sensor captures, including the extra bit depth that improves the shadow and highlight details. As a result, of course, Raw files require more storage space than JPEG files. Follow the instructions in your camera manual about selecting your Raw file format or make use of the JPEG file format at the highest resolution with the lowest compression possible.
In the process of saving the Raw file to the card, the camera generates a file that contains the three important elements of the camera’s settings, the image data, and the direct image data:
- Shutter speed
- Camera exposure mode
- White balance
- Color temperature
- Color mode
Direct image data
- Full 12 or 14-bit color depth
With JPEG, the camera converts or samples down the file from 12 or 14 bits to 8 bits. The potential 4,096 brightness levels recorded by each pixel are reduced to 256 brightness levels. The JPEG therefore loses fine details and is ill-suited for major color or brightness changes in Lightroom or Photoshop.
As mentioned earlier, compression is also a choice when it comes to JPEG files. JPEG by classification is a lossy format, meaning it creates smaller file sizes by simply eliminating some data. If compression is set to a low level (say 2:1), then there is very little data loss. High compression at 20:1, on the other hand, reduces the overall quality of the image and in some cases can introduce digital artifacts—see the example of extreme JPEG compression in FIGURE 1.7. DSLR cameras normally offer three different JPEG compression levels: Good, Better, and Best—or Basic, Normal, and Fine.
A JPEG file can in many cases produce very high quality prints. There are in fact numerous valid reasons why one would want to shoot JPEG files. Wedding photographers rarely print images above 8 × 10 inches, so the Raw file format might be a bit of overkill in that particular case. It would be wrong to say that it’s not possible to achieve good results with the JPEG file format. But critical attention to exposure and white balance (WB) is certainly required to achieve the best image quality.
Reasons for Shooting in JPEG
- Files are smaller, so more of them fit on a memory card
- Image quality is more than sufficient for certain types of photography, such as weddings, family snapshots, and spot news images
- Small files are more easily transmitted via email
- Some photographers don’t have time to post-process their files (see next section)
Reasons for Shooting in Raw
The biggest advantage of capturing images in Raw is the high-bit image post-processing advantage. What is post-processing? A Raw file is like undeveloped film. The photographer can process and extract the best possible image quality from it, and the original file can be processed differently again and again. Think of a Raw file as your negative, which can be processed after exposure in a variety of ways.
Raw files do not have a set white balance. They are only labeled with the camera setting at the time of capture. So any WB can be changed during the post-processing of the file within the Raw converter software without any image degradation. This is extremely important when editing an image. The more values you have to work with when enhancing an image, the less image destruction occurs in the post-processing stage.
Adjusting a JPEG 8-bit image file for, say, shadow detail, will exhibit what’s called posterization. This posterization shows up as abrupt changes in transition tones (called banding) rather then the smooth transitions between tones that can achieved with Raw images.