In details, for my above mentioned camera worth 670 USD, i will have to pay the duty amount 142 QAR in round figure. this is the duty for the CIF Doha. ie. 670(Cost)+4(Insurance)+100(Freight)=774. and rate of exchange is 1USD=3.65020 QAR. Therefore 5% of 774 USD (774x3.65020)x5%=141.26274 QAR.

In addition to this. there will be a legalization charge which you can find in the below link.
http://www.qatarembassy.net/page/legalization-of-legal-and-commercial-do...

Calcualation is as per below.
for CIF commercial invoice value less than $ 1,373.00, the charge of legalization will be 28 $ + legalization charge for country of origin is 42 $. So total 70$ is legalization charge for CIF Value less than $ 1,373.00