The Exchangeable Image File Format or EXIF is a specification for the file format for images taken by digital cameras. In other words, whenever you press the shutter of a digital camera, it will write the EXIF info for the photo. Most film cameras don't record that information.
Generally speaking, the EXIF info is a specification or shooting information for an image file. Camera's manufacturer and model, image width and height, and date and time are examples of attributes or tags of EXIF information. Some tags like F-number and focal length are really important for photo analysis.
You can view EXIF data easily on Microsoft operation systems (XP and Vista) and Mac OS. Also, there are many tools that can both view and edit EXIF data. Usually, you have to pay for them. One of the best EXIF viewers is Opanda IExif. Good news, it's free!
We recommend that before you upload photos to websites, you should remove the EXIF info if you don't want to reveal a camera model, camera settings, or even date/time photo were captured. In contrast, if you submit your photo for some reviews, keeping the EXIF is very useful for reviewers.
Note that, if you copy, cut, and paste the image, you may lose its EXIF. In addition, if your photo has been edited by image editor software such as Photoshop, the information like "Edited by Photoshop" will be added to the original EXIF.
Below figure shows EXIF info for an image taken by Canon PowerShot S5 IS. The left one is the original data. The right one is the EXIF data after the image was resized by the Photoshop CS3.
By studying the EXIF info of your Canon PowerShot, you might learn something you missed, and those may lead you to the next level of photographer.
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