Rational values are stored as a fraction. And the current calculation was not as precise as possible. I have modified the calculation to make it more precise. I just created a unit test with the value from your example and it passes without a problem. The only down side to this is that it will decrease the performance of the application because the value is calculated. And that is why I have added a new boolean to disable this behavior to the ExifProfile class.
EDIT: I did some more tests and it has quite an impact on the performance so I will set the option to disabled by default for now. I might change this later if I have a quicker calculation. You can enable it with the BestPrecision property in the next release.
EDIT: I did some more tests and it has quite an impact on the performance so I will set the option to disabled by default for now. I might change this later if I have a quicker calculation. You can enable it with the BestPrecision property in the next release.