What kind of data is saved in the Exif information of image files?
Photos taken with smartphones or digital cameras can store a lot of metadata, such as the date and time the image was taken, the camera used, and the aperture value. Engineer Harley Turan explains the image file format ``Exif'' that stores this data.
Exploring EXIF – Harley Turan
Mr. Turan said that he has taken 73,281 photos in the past 14 years, and he picked up one of them and shared it with metadata. Also, by accessing the above website, you can upload your own images and find out their Exif information.
The following ``flower photo'' prepared by Mr. Turan includes ``number of sample bits: 8,'' ``1280 x 960 pixels,'' ``3-color composition,'' ``data compression method: YCbCr 4:2:0,'' and ``name of manufacturer of photographic equipment.'' ：Apple'' ``Model: iPhone 12 Pro'' ``Image direction: Top right'' ``Width resolution: 72'' ``Height resolution: 72'' ``Resolution unit: inches'' ``Software: 16.6 (iOS)'' ``Date and time of shooting : August 13, 2023 13:07:57' 'Host device: iPhone 12 Pro' 'Tile width: 512' 'Tile length: 512' 'YCC configuration: Center' 'Exif tag: 258' 'GPS tag: 2224' 'Exposure time: 1/856' 'F value: f/2' 'Exposure program: Normal' 'ISO speed rate: 25' 'Exif version: 0232' 'Original data generation date and time: August 13, 2023 13 'Digital data creation date and time: August 13, 2023 13:07:57' 'Offset: +01:00' 'Original offset: +01:00' 'Digital data offset: +01 :00' 'Shutter speed: 1/856' 'Brightness: 9.10714795263233' 'Exposure compensation value: 0' 'Metering method: Pattern' 'Flash: Auto flash on but no flash' 'Lens focal length: 6mm' 'Subject area X :2004, Y: 1514, Width: 2318 Height: 1393' 'Maker note: Raw maker note data' 'Shooting date and time subsec: 524' 'Original subsec: 524' 'Digital data subsec: 524' 'Compatible flash Pix version: 0100' 'Color space: No measurement' 'Effective image width: 4032' 'Effective image height: 3024' 'Sensor method: One-chip color area sensor' 'Photography method: Direct shooting' 'Exposure mode: Auto 'White balance: Auto' '35mm equivalent lens focal length: 52' 'Scene type: Standard' 'Lens specifications: 1.5399999618512084-6 mm f/2.4' 'Lens manufacturer: Apple' 'Lens model: iPhone 12 Pro back triple camera 6mm f/2' 'Composite: General Composite Image' 'Latitude: 51.11505833333334 north' 'Longitude: 0.5824055555555555' 'Altitude: 58.61263655152052 m above sea level' 'Speed: 0km/h' 'Direction of image taken: 183.54121405750 8 degrees ''Destination direction: 183.541214057508 degrees' 'Horizontal positioning error: 3.5355339046563916' 'CMM type: Apple' 'Profile version: 4.0.0' 'Color space: RGB' 'Position space: XYZ' 'ICC signature registry: acsp 'Primary Platform: Apple' 'Device Manufacturer: Apple' 'Rendering Intent: Perceptual' 'Profile Creator: appl' 'ICC Profile: Apple Wide Color Sharing Profile' 'ICC Copyright: Copyright Apple Inc., 2016' A lot of information is recorded
As Mr. Turan showed, thanks to Exif information, information such as the shooting equipment and lens can be obtained from a single photo, and the shooting settings such as shooting time, latitude and longitude, white balance and ISO sensitivity, etc. You can check a wide variety of information later, such as the direction of time.
Some information is specific to Apple cameras, including the altitude at which the photo was taken, how fast the camera was moving, how much signal-to-noise the camera sensor captured, how long the camera was up, the distance from the camera to the focal point, and the camera It is also possible to understand 3D vectors that indicate longitudinal, vertical, and horizontal acceleration of the object. Based on this information, Mr. Turan next made an attempt to search for images based on Exif information.
Mr. Turan wrote his own script and succeeded in finding and outputting images that met specified conditions. For example, this is one of the photos that came up when I searched for ``No region settings,'' ``Descending order,'' and ``Photos with the most faces.''
'Photos where the subject is too close to focus' with 'maximum focal length'
'RunTimeValue (starting time) is the largest', that is, 'a photo with the shortest time spent from turning on the mobile phone to taking the photo'
'Photo with the fastest camera movement speed when taken'
By adding altitude to the conditions, you can search for 'photos of the fastest time on land.'
Search for 'photo taken when dropping a cell phone' based on acceleration vector
In addition, by combining Exif information, it is possible to not only place the location at the time of shooting on a map, but also to display the field of view at the time of shooting in 3D.
As mentioned above, Exif can provide a variety of information, and Turan says, ``If you were to post a photo of a friend's apartment online, you would not only provide the image itself, but also the latitude, longitude, and altitude. 'If GPS accuracy is high, it is quite possible to find the apartment where the photo was taken.'
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