Technical The Exif format has a number of drawbacks, mostly relating to its use of legacy file structures. • The derivation of Exif from the TIFF file structure using offset pointers in the files means that data can be spread anywhere within a file, which means that software is likely to corrupt any pointers or corresponding data that it does not decode/encode. For this reason most image editors damage or remove the Exif metadata to some extent upon saving. • The standard defines a MakerNote tag, which allows camera manufacturers to place any custom format metadata in the file. This is used increasingly by camera manufacturers to store camera settings not listed in the Exif standard, such as shooting modes, post-processing settings, serial number, focusing modes, etc. As the tag contents are proprietary and manufacturer-specific, it can be difficult to retrieve this information from an image or to properly preserve it when rewriting an image. Manufacturers can encrypt portions of the information; for example, some Nikon cameras encrypt the detailed lens data in the MakerNote data. • Exif is very often used in images created by scanners, but the standard makes no provisions for any scanner-specific information. • Photo manipulation software sometimes fails to update the embedded thumbnail after an editing operation, possibly causing the user to inadvertently publish compromising information. For example, someone might blank out a licence registration plate of a car (for privacy concerns), only to have the thumbnail not be updated, meaning the information is still visible. • Exif metadata are restricted in size to 64 kB in JPEG images because according to the specification this information must be contained within a single JPEG APP1 segment. Although the
FlashPix extensions allow information to span multiple JPEG APP2 segments, these extensions are not commonly used. This has prompted some camera manufacturers to develop non-standard techniques for storing the large preview images used by some digital cameras for
LCD review. These non-standard extensions are commonly lost if a user re-saves the image using image editor software, possibly rendering the image incompatible with the original camera that created it. (In 2009, CIPA released the
Multi Picture Object specification which addresses this deficiency and provides a standard way to store large previews in JPEG images.) • Prior to version 2.31 (July 2016) there was no way to record time zone information for an image, resulting in ambiguity. For example, a camera might record the "DateTimeOriginal" value using its local time zone, but a program reading the file later could mistakenly interpret that time as UTC. • There is no standard field to record readouts of a camera's
accelerometers or
inertial navigation system. Such data could help to establish the relationship between the image sensor's XYZ coordinate system and the gravity
vector (i.e., which way is down in this image). It could also establish relative camera positions or orientations in a sequence of photos. Some software records this information using the GPSImgDirection tag along with custom GPSPitch and GPSRoll tags. • The XResolution and YResolution tags provide the number of pixels per length unit for the width and height of the image, respectively. (The length unit itself is specified by the tag ResolutionUnit.) By default, these tags in combination are set to 72
pixels per inch (ppi). These tags were inherited from the TIFF 6.0 standard and are required even though for images produced by digital cameras, image resolution values such as ppi are meaningless.
Privacy and security Since the Exif tag contains metadata about the photo, it can pose a privacy problem. For example, a photo taken with a
GPS-enabled camera can reveal the exact location and time it was taken, and the unique ID number of the device - this is all done by default - often without the user's knowledge. Many users may be unaware that their photos are tagged by default in this manner, or that specialist software may be required to remove the Exif tag before publishing. For example, a
whistleblower, journalist or
political dissident relying on the protection of anonymity to allow them to report
malfeasance by a corporate entity, criminal, or government may therefore find their safety compromised by this default data collection. In December 2012,
anti-virus businessman
John McAfee was arrested in
Guatemala while fleeing from alleged persecution in neighboring
Belize.
Vice magazine had published an exclusive interview on their website with McAfee "on the run" that included a photo of McAfee with a
Vice reporter taken with a phone that had geotagged the image. The photo's metadata included GPS coordinates locating McAfee in Guatemala, and he was captured two days later. McAfee later claimed to have edited the Exif data from his phone to provide a false location. According to documents leaked by
Edward Snowden, the
NSA is targeting Exif information under the
XKeyscore program. The privacy problem of Exif data can be avoided by removing the Exif data using a
metadata removal tool. ==Related standards==