[1] In order to make the typically faint compression artifacts more readily visible, the data to be analyzed is subjected to an additional round of lossy compression, this time at a known, uniform level, and the result is subtracted from the original data under investigation.
[1] Additionally, digital data formats such as JPEG sometimes include metadata describing the specific lossy compression used.
By its nature, data without lossy compression, such as a PNG image, cannot be subjected to error level analysis.
[3] More significant, the actual interpretation of the level of compression artifacts in a given segment of the data is subjective, and the determination of whether editing has occurred is therefore not robust.
[4] In May 2015, the citizen journalism team Bellingcat wrote that error level analysis revealed that the Russian Ministry of Defense had edited satellite images related to the Malaysia Airlines Flight 17 disaster.