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These days, almost all mid-to-high end digital cameras offer the ability to capture photos in either JPEG or RAW format. This article takes a look at the pros and cons of each to help you figure out which method is best for you.
JPEG Image Capture
How your camera captures JPEG images:
First, the camera's processor applies colour, exposure, contrast, noise reduction, white balance, and sharpness adjustments to the image based on configured settings. Then the image is compressed based on the compression algorithm selected; typically that means that redundant pixels are discarded to make the file size smaller, but the amount of data loss will depend on your compression settings. You can usually select low, medium, and high JPEG compression in-camera, where the highest compression results in the most data loss (small file size), and the lowest compression results in the smallest data loss (large file size).
When you open a compressed file in an image-editing application (e.g. Adobe Photoshop), the application attempts to reverse the compression algorithm and fill in missing pixels with appropriate data, thus restoring the file to full-size. Unfortunately, the algorithm is not perfect, and actually results in a lower-quality image than what was first captured by the camera sensor. The higher the compression, the more visible the JPEG "artifacts" will be. Common JPEG artifacts are jagged edges, irregular blocks of pixels, and increased digital noise.
Pros of JPEG over RAW:
1) Using compression allows more images to fit on a memory card.
2) Low compression JPEG images usually result in excellent image quality since the JPEG artifacts are much less pronounced.
3) If using continuous shooting mode, you'll be able to shoot more images in a given burst because it will take more of them to fill your buffer, and they will be written faster to memory card so the wait until the next shot won't be long.
4) Images can be downloaded and printed immediately, without editing in Photoshop or similar application. If editing is required, it is usually quick and only one application is required.
Cons of JPEG:
1) Printing high-resolution images from JPEGs with medium to high compression can result in visible artifacts unless the captured scene has a great amount of similar pixels in it (e.g. a photo of a blue wall).
2) Overexposed or underexposed images cannot be fixed - the detail in very bright or very dark areas is lost forever.
RAW Image Capture
How your camera captures RAW images:
Your camera records pixel data right off the sensor and saves it in a proprietary format. Canon's proprietary format is CRW, and Nikon's is NEF, but all brands have their own format. If RAW compression is deployed by your camera, it will use a "lossless" method, such that no data loss occurs and no artifacts will occur as a result.
When you open a RAW file on your computer, you must use an image-editing application that understands your proprietary RAW format (i.e. Canon RAW files need a different converter algorithm than do Nikon RAW files). In the image editor, you will be able to modify colour saturation, exposure levels, contrast, white balance, and sharpness, at a minimum. Once you are happy with your image, the special software converts the raw data into an internationally recognized file type such as a 16-bit TIFF or PSD.
Pros of RAW over JPEG:
1) Control, control, control. You have the ability to modify image data post-shoot to correct colour saturation, exposure levels, contrast, white balance, and sharpness. This means you can actually fix an underexposed or overexposed image. You can also reduce noise levels for images shot with a high ISO.
2) And the ability to save the image to a 16-bit TIFF as opposed to an 8-bit JPEG gives you thousands of different brightness levels versus only 256.
Cons of RAW:
1) RAW files take up a large amount of space, so not many will fit on a memory card, especially when compared to a JPEG.
2) You will also need to take an extra step when processing your image to convert the image from RAW to TIFF or PSD. Each manufacturer has their own software to do this, based on the proprietary format in which the original image was saved.
3) Be careful about converting your RAW image to a 16-bit TIFF image, though, since most applications do not support many tools (if any) with 16-bit images. Photoshop CS2 and Apple's Aperture have full support of 16-bit images, while GIMP, Picture Window Pro 3.5, and Paint Shop Pro X provide limited support of 16-bit images, but older version of Photoshop (back to 6.0) only have a small amount of tools available, and certainly no layers support.
Conclusion:
JPEG capture is best for bursts of shots (e.g. sports or wildlife photography) and in cases where your memory card space is low. Be sure to use low JPEG compression (large file size), as it will not likely result in visible JPEG artifacts.
RAW images are best for shots that you can never re-take (e.g. you'll never return to Iceland in your lifetime, or it's an important wedding) or when lighting conditions are poor. You need to be sure you have enough memory card room to take all the shots you want, and enough space on your computer to handle the RAW and TIFF formats at the same time.
Jennifer Clarkson is a Canadian Photographer living in Ottawa. To read more of her Photography Tips and articles, or to browse her Photography Forum, please visit her website at www.jclarksonphotography.com. |
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