effective focal length field

The exif value for focal length does not take into account the camera's "crop factor". I've seen one other posting on this, with no real solution. It seems to me that this would be easy to fix, regardless of how Gallery gets the focal length. If gallery simply retrieves the data from another tool such as exiftags, my thought was that the easiest way to do this would be to simply create a custom field that uses that same focal length, and then multiplies it by the crop factor that I choose. In my case, my custom field would just take the focal length and multiply it by 1.5 to come up with the effective focal length. Sounds easy, but I'm not familiar with the Gallery code and I'm just beginning to investigate this. I was hoping someone already solved this issue and would save me the time

Thanks,
Vern