This is the section of the original SR-71 operation manual that describes in detail how the camera works. The plane was equipped with an Optical Bar Camera
"The Optical Bar Camera (OBC) is a high resolution panoramic camera
with a "folded" ----------- lens system. It provides continuous
------- or --------- coverage along the flight track through an angle of 70 degrees on each side of the aircraft.
Note: the ----- are blacked out sections in the manual.
The manual goes on to talk about the operations of the camera and also notes that it takes 5 inch film with is way bigger (and subsequently higher "resolution") than the 35mm you would use in a home camera.
Here are the actual cameras. The left is the Technical Objective Camera and the right is the Optical Bar Camera.
The resolution of the TEOC was pretty great
Programmable system with a 48 inch focal length. The TEOC resolution
was 110 lines per millimeter, which equates to about 6" ground
resolution from an operational altitude. The TEOC's were mounted both
sides of Chine controlled by a computer
The OBC seems like it may have been more size than resolution
The OBC could photograph 100,000 square miles of the Earth's surface
per hour. Film image 72 miles wide, & film length 10,500ft.
And of course you cant have a fancy plane with out lots of buttons and knobs. The control systems for the cameras looked like this
For what its worth it seems that both of these cameras were really high tech panning control systems for cameras. They are very similar to Equatorial Mount cameras which are used to photograph stars (since the earth is moving), it's also called a barn door tracker.
(image source, all images)