What is EXIF data and other metadata in photos and videos
EXIF (Exchangeable Image File Format) is a
standard for storing interchange information in digital photo files. Data such as shutter speed, exposure
compensation, F number, what metering system was used, if a flash was used, ISO number, date and time the
image was taken, whitebalance, auxiliary lenses that were used and resolution are stored by digital cameras.
Every time you take a picture with your digital camera or phone, a file (typically a JPEG)
is written to your device’s storage. In addition to all the bits dedicated to the actual picture, it records a
considerable amount of additional metadata. This data usually includes date, time, camera settings,
geolocation coordinates, orientation, etc. Photo processing software, like Photoshop, can also add further
metadata to EXIF.
A lot of this stuff is mundane, but it also can contain potentially sensitive information,
like geolocation data (GPS coordinates where the picture was taken). That means, if you are sharing images
with metadata there is a lot of details others can glean from them, expecially geotagged data. Moreover, this
information increase the file size, specially with small images like the ones used on responsive web designs.
- A right image optimization process removes all this information before compressing the image. -
Viewing EXIF data and other metadata
You cannot stop EXIF metadata from being added to your photographs and videos. It is also a
good practice to save this information, since it provides useful information to manage your photo gallery
later. Creation dates, geotagging, and camera settings and orientation are valuable data which can be removed
later, when the images and videos are shared and published.
One of the most powerfull tools to view metadata information is ExifTool. This open source tool is a platform-independent command-line
application for reading, writing, and editing metadata in a wide variety of files. ExifTool works on Windows,
MacOS, and Linux and it supports many files types (JPG/JPEG, TIFF, GIF, PNG, PSD, BMP, RAW, CR2, CRW, PICT,
XMP, DNG, MP4, MOV) and different metadata foramts including EXIF, GPS, IPTC, XMP, JFIF, GeoTIFF, ICC Profile,
etc. as well as the maker notes of most of digital cameras.
Privacy and geolocation data
Geolocation data are useful for geotagging, which creates all kinds of new possibilities,
such as allowing users on photo-sharing sites to see any images taken in specific locations, view where your
pictures were taken on a map, and to find and follow social events. Howevere they are a data leak when they
are directly shared on the Internet.
Photographers and photo settings
Metadata are specially sensitive for photographers, where lots of information are shared in
it, like location and camera settings. This kind of information is very useful to day-to-day work, but it must
be removed when the image is published and distributed to avoid private and professional data leaks, like with
EXIF orientation and web optimization
When images are photographed, digital cameras use orientation sensors to store an EXIF
orientation value for how camera is held. This information is used later to automatically rotate your photos,
saving you of this manual task.
There are 8 possible EXIF orientation values, which reflect the position of the camera with
respect to the ground, numbered 1 to 8:
How the 8 possible EXIF values look for the letter F (credit to Dave Perrett)
|1||0 degrees||the correct orientation, no adjustment is required.|
|2||0 degrees, mirrored||image has been flipped back-to-front.|
|3||180 degrees||image is upside down.|
|4||180 degrees, mirrored||image is upside down and flipped back-to-front.|
|5||90 degrees||image is on its side.|
|6||90 degrees, mirrored||image is on its side and flipped back-to-front.|
|7||270 degrees||image is on its far side.|
|8||270 degrees, mirrored||image is on its far side and flipped back-to-front.|
In the 7 scenarios – 2, 3, 4, 5, 6, 7, 8 – the image need to be rotated before orientation
stripped. Most common photo management programs read EXIF orientation to show photos on the right position.
However, browsers don't perform this task, which means that the image or photo must be rotated before web
When you rotate or flip an image, EXIF orientation must be removed. Most programs do this
task correctly, however some programs don't: like Windows Photo Viewer or Microsoft Paint. If you have some
problems with photo rotation, you must fix this issue with a editing software like Photoshop, GIMP, or OSX
Removing EXIF metadata
Metadata waste several kilobytes and result in data leak. This is why is recommeded to
remove EXIF data when images are published and distributed. Morevoer, images need to be rotated and correctly
compressed for web pusblishing. To automatically perform all this tasks, you can easily take advantage from
our export tool, and get perfectly optimized images for web.