turtleduck
Hello turtleduck,
Signature scanning is one of the methods of finding lost data on a disk. To do this, a signature scanner goes through the memory blocks of the media, looks for signatures of files encoded by the developer, and completely ignores the file system. Each software has its own list of recovery signatures (usually listed on the developer's website as files supported).
File signatures are unique bits of files that characterize certain types of files. Each file type has its own unique file characteristics at the beginning and end, so the program is able to find files knowing where the file starts and ends.
Different data recovery programs have different 'scanners' for finding files on the disk (they may have different names depending on the manufacturer). In general, the following types of file scanners can be distinguished: Quick, Deep, and Signature.
- Quick scanner searches for recently deleted files, for example, files from emptied Recycle Bin or files deleted via Shift + Delete. In this case, file format is not important, as the scanner uses file system records to search for data.
- Deep scanner is similar in principle to Quick, as it also uses file system entries to search. But additionally includes cases of replaced file system with either a new one or reformated as the same type. Or the drives with file system that have become RAW. Usually data recovery software still can find the remnants of the file system on them and retrieve original file names and folder structures.
This means that the list of supported files applies only to the Signature scanner since all other 'modes' can recover any type of file as long as records of it are still in a file system or whats left of it.
Signature scanner itself is a part of Deep scanner and, as you may have already realized, it responds to file recovery based on a different principle, not relying on the file system or its remnants.
Modern data recovery software successfully combines all of the above scanning modes to scan your disk so that you end up with the maximum number of results.
As for the PhotoRec, this program indeed uses only signature file search. There is an option to specify the file system in the program, but it's made only to scan free disk space and it has nothing to do with file search. So it will not have any impact on data recovery chances and quality.
