Blank NULL? Or blank zero characters? You can certainly use ISNULL, but if you care about performance more than simplicity, go for the union.
SELECT *
FROM TableA TA, TableB TB
WHERE
TableA.Name = @Name
AND TA.ColumnF = TB.ColumnF
UNION ALL
SELECT *
FROM TableA TA, TableB TB
WHERE
TableA.Name = @Name
AND TA.ColumnF = '000000' AND TB.ColumnF = ''
(if blank is NULL, that final "=''" would be an 'IS NULL')