For me personally, with photos, I don't use a backup application to backup my files.
Instead, I run a utility like robocopy (which comes with 7) to make a duplicate copy of my files on the external drive. I create a batch file on my hard drive with syntax similar to the following
C:\windows\system32\robocopy.exe C:\pictures X:\backups\pictures /E /MIR
C:\windows\system32\robocopy.exe C:\movies X:\backups\movies /E /MIR
With robocopy, the first run takes a while as it copies over the files. All subsequent runs are fast as it only gets files that are updated or have changed since the last run. With the /MIR switch, if you delete a file on your source drive, it will also delete it from your destination drive when you next run the job.
I keep 2 external drives, (offsite) and plug them in occassionally and run the above batch file. Been using this method for years and years and years and it's solid (for me).