Sometimes it will sometimes it won't. Depends on the charactersets - if the export is a subset of the characterset in the target database then the binaries will attempt to convert. Otherwise you will need to switch the characterset on the during the export.

For example:

I am assuming a Unix type machine. Under windows I think you will need to change a registry key or something but I am not sure.

1) change the environment variable of NLS_LANG to that of your target database:

echo $NLS_LANG
export NLS_LANG=AMERICAN_AMERICA.WE8ISO8859
echo $NLS_LANG
AMERICAN_AMERICA.WE8ISO8859P1

2) do your export. You should see something like this before the data starts to get exported:

Export done in WE8ISO8859P1 character set and UTF8 NCHAR character set
server uses UTF8 character set (possible charset conversion)

3) now you should be able to import the dmp file into your target database.

Conversely you can do this on the import too. Change the NLS_LANG variable before importing and this should convert the dmp file but I personally think it's easier doing this on the export.

In Windows (dos really) you do:

set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1

Then do the export.

HTH