ELA Amplification Factor
Definition
The multiplier applied to the per-pixel difference before display. A higher factor reveals subtle differences but also amplifies noise, making regions look manipulated when they are not. The standard FotoForensics factor is around 10x.
- Function
- Multiplier on per-pixel difference
- Typical default
- Around 10x (FotoForensics)
- Tradeoff
- Higher factor amplifies noise too
- Used in
- Error Level Analysis (ELA)
Common questions
Why can a high amplification factor produce a false impression of tampering?+
Amplifying the difference makes low-level compression noise, JPEG block edges, and normal texture variation visually prominent alongside any genuine splice, so an untrained viewer can mistake an unedited but noisy region for a manipulated one.
Should the same amplification factor be used for every image?+
No, the right factor depends on the image's original compression quality and content; an examiner typically tries several factors and cross-checks any suspicious region against other evidence rather than relying on a single fixed multiplier.
Related terms
- Compression Equilibrium
- The state of an image region after sufficient JPEG compression cycles at a given quality: further compression at the same quality produces...
- ELA (Error Level Analysis)
- A passive image forensics technique that re-saves the input image at a chosen JPEG quality and amplifies the per-pixel absolute difference to...
- False Positive (ELA)
- An ELA anomaly in a region that was not manipulated, typically caused by high-frequency texture, JPEG artefacts in the original, or camera...
- High-Frequency Detail
- Fine textures, sharp edges, and small text that JPEG compresses poorly. These regions inherently show high ELA values in authentic, unmodified images...
- Saturation
- In ELA context, the condition where a region's error level has reached near-zero, indicating it has already been compressed to near-equilibrium. A...