Category: Radio & Media
Written by Will Farrar
Today we are going to take a look at how you can find inconsistencies in NASA images & virtually any image that is a JPEG or PNG file.
- ELA (Error Level Analysis):
What is ELA: Error Level Analysis (ELA) is an algorithm that evaluates the error level potential of a JPEG image. JPEG is a lossy image format; every resave degrades the picture. The amount of degradation varies based on the number of saves. The first save loses a lot, the second save loses a little more, and by the 20th save, it is probably as low quality as it will ever get. When a picture is modified, the changed parts have a higher error level potential than the rest of the image. ELA works by saving the picture at a known quality level (like a JPEG at 95%), and then determines how much changed. Edits and splices appear as regions with more change.
How to run a NASA JPG or PNG through ELA:
1) Browse the Internet to the NASA JPG or PNG file that you wish to retrieve the Analysis of and then select the URL at the top of the browser and copy it to your clipboard.
2) Open the website http://www.fotoforensics.com and paste the NASA URL into the space marked "Image URL:" and click the "Upload URL" button.
3) You will now see the NASA Image at the top of the page with the ELA selected on the right. Directly below the Image is the ELA version of the image. You can hover your mouse over the original NASA image and the ELA will appear directly in front of it which makes it easier to compare where there may be image manipulation done. The Digest, JPEG% & Metadata will also give you important information that may be useful when trying to decide if an image has been manipulated.
Learn more by using the extensive tutorial: http://fotoforensics.com/tutorial.php
Are you ready to give it a shot?
Try out these practice challenges and find out your current skillset:
Before using ELA to interpret anything it is best to read the FAQ as well as complete the Challenges that FotoForensics have put together to really help you train your eyes and mind to focus on finding something that is out of place! Open http://fotoforensics.com/messages.php?challenge and have fun learning how to spot image tampering via Error Level Analysis!
More reasons that we use Error Level Analysis: