Taken from the FAQ section on Carnival website; it appears only on select ships; see below in bold. They don't mention the costs... it wasn't available on the ships that I recently sailed with them.
How much are photos on board?
The Ship's Photographers take both candid and posed shots all during the cruise. The photos are then put on display, usually the very next day, and are available for purchase (with a Sail & Sign Card), prices vary by size. Special requests can be made by appointment and are available for a fee. Film is available in the Duty-Free shops for purchase.
One-day developing service is available for the following types of film. Drop-off boxes are located at the Photo Gallery:
Panorama and APS Advantix Film can be processed on select ships; check with the Photo Manager for details.
Developing film onto a CD (select ships: Spirit Pride Conquest Legend Glory).
Carnival Victory March 9, 2013
*carnival dream *
Glory 2/28/2010: Dina & Marty
Valor Feb 2009: Dina & Marty - again
Grandeur Feb 2008: DTW, Dina & Marty
Inspiration May 26, 2007
Fascination: Feb 2007
Enchantment of Seas: Sept 2006
Radiance of the Seas
Majesty of the Seas
The Big Red Boat