Colour print film is widely available and prices are pretty reasonable al about US$2.50 for a roll of 36 print film. Slide film can be bought in Hanoi and HCMC, but don't count on it elsewhere. Supplies of black-and-white film are rapidly disappearing, so bring your own.
Photo-processing shops are located all over Vietnam and developing costs are about US$5 per roll depending on the print size selected. The quality is generally very good. Processing slide film is best saved for somewhere else.
Cameras are fairly expensive in Vietnam and the selection is limited. Happily, batteries and digital-camera memory cards are readily available in large cities.
The Vietnamese police usually don't care what you photograph, but on occasion they get pernickety. Obviously, don't photograph sensitive sites such as airports and border checkpoints. Don't even think of trying to get a snapshot of Ho Chi Minh in his glass sarcophagus!
Photographing anyone, particularly hill-tribe people, demands patience and the utmost respect for local customs. Photograph with discretion and manners. It's always polite to ask first and if the person says no, don't take the photo. For endless tips on better travel photography, pick up a copy of Lonely Planet's Travel Photography