Notes from the Gallery Floor

Cue marks. They appear in the upper right of the frame near the end of a reel: the first about eight seconds out to start the next projector's motor, the second about one second out to trigger the changeover. See Room 2.

Yes. Kodak still produces motion picture camera negative such as Vision3 500T 5219 and print stock. Fujifilm ended most motion picture film production in 2013.

Cellulose nitrate is highly flammable and produces its own oxygen when burning, so it cannot be smothered. It is stored in specialised vaults and projected only in licensed booths, such as the Dryden Theatre in Rochester.

The chemical breakdown of cellulose acetate film, which releases acetic acid. Affected film smells of vinegar, shrinks and becomes brittle. Cold, dry storage slows it considerably.

A 2,000-foot 35mm reel runs about 22 minutes at 24 frames per second. Older 1,000-foot reels ran about 11 minutes.

Often, yes. Film grain moves randomly from frame to frame, and projected film has slight weave and a particular way of handling bright highlights. Whether that is better is a matter of taste; we simply encourage looking closely at both.

Check size, fold lines and printer codes. Many US originals carry a National Screen Service year/number code in the lower margin. For valuable pieces, consult a specialist dealer or auction house. More in Room 3.

Repertory cinemas such as the Prince Charles Cinema in London, Film Forum in New York and the New Beverly Cinema in Los Angeles, plus archive screenings and festivals like Il Cinema Ritrovato in Bologna. Check listings for the format.

Many collectors use 16mm or 8mm projectors at home. 35mm home projection is rare and needs space, maintenance and care. Never attempt to project nitrate outside a licensed booth.