Most errors are recoverable, and are simply logged as issues. (Visit /resizer.debug.ashx to see the log). Duplicate issues are not logged.

Some errors are not recoverable:

InterceptModule (These errors 

- ImageProcessingException (500)  - No caches configured
- ImageProcessingException - no image encoders found
- ImageProcessingException  - cache file locked, timeout occured.
- ImageCorruptedException (wrapping an ArgumentException, ExternalException) - Source file corrupted
- ImageMissingException (404) - source file/resource missing (Can occur and different points, for example in watermarking, or in http-based VPP.
- Intercept module converts FileNotFoundExceptions to 404 ImageMissingExceptions

(ImageBuilder) Exceptions

- FileNotFoundException - file not found
- ImageCorruptedException (wrapping an ArgumentException, ExternalException) - Source file corrupted
- ImageProcessingException - no image encoders found


(SizeLimiting plugin)
- SizeLimitException - the image exceeded configured total resolution limits.

(S3Reader)
FileNotFoundException (recoverable with image404 plugin)

(SqlReader)
FileNotFoundException (recoverable with image404 plugin)
Sql* errors, configuration problems