Declare are the item on the customs declaration form that is given in the Aircraft and do not go thru the green chanel as that will be the first mistake.Be polite to the customs and inform that this will be bought back and Inform the customs photographic equipment is cheaper in India .If the customs officials trouble you please go to the customer service/grienance cell and lodge a complain against the officials as their names are displaced on their badges.
One more peice of advice is to declare all the photographic equipment along with their serial numbers at the customs on the way back saying its being taken out of the country and you will have no issues when back as long as you do not misplace the document. Also go thru the latest online documention regarding customsof dos and don'ts.