Right to privacy has been recognised to be incidental to Fundamental Rights and hence everyone is conferred with the right; it is not a right that is conferred.
A citizen does not lose the right to privacy just because he or she happens to be at a public place. No action which specifically interferes or intrudes into the privacy of a person constitutes a civil wrong and hence a civil action lies.
Yes there is nothing wrong if a person takes photo or makes a video in a public garden. However, if the endeavour focusses on a person or group of persons, the said act could only be with the express permission of those persons. Else, in my understanding, the act is a certain civil wrong.