Related Clues:

• Blowup source, briefly
• Studio orig.
• Opp. of 52 Across
• Minus: Abbr.
• No. beginning with a "-"
• Less than zero: Abbr.
• Pic source
• Subzero (abbr.)
• Like nos. below zero
• Darkroom item, for short
• Minus (Abbr.)
• Ö, on an AA batt.
• Darkroom master (Abbr.)
• On the left half of the no. line
• Batt. terminal