Friday, October 07, 2005

Which File Format Is Best?
Digital Photography Bonus Secretby David Peterson
-->Most modern digital cameras give you a choice of file formats when saving your image. It's very helpful to know the benefits (and disadvantages) of each file format so you can make the best decision on the file format to save your images in.
Why do we need file formats?A standard photo taken with a 4.3 megapixel camera has 4.3 million little pixels, or pieces of information, that comprise the image. Each of those pieces needs to store a red, green and blue color value so the color of the pixel can be recreated by a computer or printer. Each color value records the strength of that color on a scale from 1 to 256.
This is a lot of information! Each pixel needs three bytes to store the three color values, and there are 4.3 million pixels. 4.3 million times 3 is around 13 million bytes, or 13 Megabytes.
If each image took 13 Megabytes of storage, you'd run out of space pretty quickly on your memory card! So the file formats used to save images compress the image down to a smaller, more manageable, size.

JPEGThe JPEG, or JPG format was invented to help make image sizes more manageable. JPEG is the most popular format used in digital cameras today because it's a simple and versatile format, and is supported by all image related software.
JPEG works by compressing the image to a much smaller size at the expense of some image quality. Normally you won't see any difference because the JPEG format looks at the image and removes only the information that it can recreate by looking at adjacent pixels when the image is displayed again.

You can specify the amount of compression with JPEG images. Your camera will usually have a quality setting - low, medium or high. Low quality increases the JPEG compression, and although your images will be smaller, they won't look at good.

Uncompressed TIFFTIFF is another file format popular because while it still compresses the image, it does so in a way to ensure that the full image can always be restored. There's no loss of image quality. It works in the same way as ZIP files on a computer. They are compressed, but you can always get the original file back.

RAWImages stored in RAW format are exactly what the camera 'sees'. There is no processing done by the camera before the image is saved. This is one of the major advantages of RAW.
Remember when I said above that each color value strength is stored on a scale from 1 to 256? Modern cameras can actually detect more than 256 levels of strength. But since the TIFF and JPEG formats don't allow more than that number, the camera throws the extra information away. The RAW format saves these extra strength levels resulting in a better image with more contrast levels.

There's another advantage - the camera doesn't correct for exposure or white balance before it saves in RAW format. Meaning you have ultimate control in manipulating the image in a paint program - so your image looks exactly how you want it to look.
All these advantages come at a cost. RAW images don't use any compression so they are large files and take a long time to store and copy. Also, there is no single RAW standard for all cameras, so you usually will need to use your camera manufacturer's software to read the RAW file.

Which format should I use?While TIFF and RAW do give you superior images, I personally don't think the hassle of much larger file sizes are worth it unless you have a really high end camera and need to produce really large prints. Not only do the images take longer to save, but you need to purchase larger (and more expensive) memory cards; a larger hard drive; and more CDs to back up to.

The JPEG format is the most popular - and it's not hard to see why. It provides a much smaller image size without losing a lot of quality. I recommend using the JPEG format set to high image quality on your own camera.

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