Do you post pictures online? E-mail them to friends? When you do you might be sending more information than you think.
Take a look at the information below, this is all from a single picture I took with my phone. This information is embedded in the image as metadata and is used by various applications and tools.
Take a look over the information and I’ll explain more below.
File Size : 2.1 MB File Type : JPEG MIME Type : image/jpeg Exif Byte Order : Big-endian (Motorola, MM) Make : Apple Camera Model Name : iPhone 5 Orientation : Rotate 90 CW X Resolution : 72 Y Resolution : 72 Resolution Unit : inches Software : 7.1.1 Modify Date : 2014:05:03 11:32:20 Y Cb Cr Positioning : Centered Exposure Time : 1/847 F Number : 2.4 Exposure Program : Program AE ISO : 50 Exif Version : 0221 Date/Time Original : 2014:05:03 11:32:20 Create Date : 2014:05:03 11:32:20 Components Configuration : Y, Cb, Cr, - Shutter Speed Value : 1/847 Aperture Value : 2.4 Brightness Value : 9.095280499 Metering Mode : Multi-segment Flash : Off, Did not fire Focal Length : 4.1 mm Subject Area : 1357 1275 456 457 Run Time Scale : 1000000000 Run Time Epoch : 0 Run Time Value : 65539364512708 Run Time Flags : Valid Sub Sec Time Original : 334 Sub Sec Time Digitized : 334 Flashpix Version : 0100 Color Space : sRGB Exif Image Width : 3264 Exif Image Height : 2448 Sensing Method : One-chip color area Scene Type : Directly photographed Exposure Mode : Auto White Balance : Auto Focal Length In 35mm Format : 33 mm Scene Capture Type : Standard Lens Info : 4.12mm f/2.4 Lens Make : Apple Lens Model : iPhone 5 back camera 4.12mm f/2.4 GPS Latitude Ref : North GPS Longitude Ref : West GPS Altitude Ref : Above Sea Level GPS Time Stamp : 18:32:11.58 GPS Img Direction Ref : True North GPS Img Direction : 356.9633028 Compression : JPEG (old-style) Thumbnail Offset : 1254 Thumbnail Length : 9119 Image Width : 3264 Image Height : 2448 Encoding Process : Baseline DCT, Huffman coding Bits Per Sample : 8 Color Components : 3 Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2) Aperture : 2.4 GPS Altitude : 60.3 m Above Sea Level GPS Latitude : 37 deg 55' 52.24" N GPS Longitude : 122 deg 1' 51.43" W GPS Position : 37 deg 55' 52.24" N, 122 deg 1' 51.43" W Image Size : 3264x2448 Run Time Since Power Up : 18:12:19 Scale Factor To 35 mm Equivalent: 8.0 Shutter Speed : 1/847 Create Date : 2014:05:03 11:32:20.334 Date/Time Original : 2014:05:03 11:32:20.334 Circle Of Confusion : 0.004 mm Field Of View : 57.2 deg Focal Length : 4.1 mm (35 mm equivalent: 33.0 mm) Hyperfocal Distance : 1.89 m Light Value : 13.3