The Big Box o’ Optics disgorged an ancient new-in-box Computar 4.8 mm lens, originally intended for a TV camera, with a C mount perfectly suited for the Raspberry Pi HQ camera:
Because it’s a video lens, it includes an aperture driver expecting a video signal from the camera through a standard connector:
The datasheet tucked into the box (!) says it expects 8 to 16 V DC on the red wire (with black common) and video on white:
Fortunately, applying 5 V to red and leaving white unconnected opens the aperture all the way. Presumably, the circuitry thinks it’s looking at a really dark scene and isn’t fussy about the missing sync pulses.
Rather than attempt to find / harvest a matching camera connector, the cord now terminates in a JST plug, with the matching socket hot-melt glued to the Raspberry Pi case:
The Pi has +5 V and ground on the rightmost end of its connector, so the Computar lens will be jammed fully open.
I gave it something to look at:
With the orange back plate about 150 mm from the RPi, the 4.8 mm lens delivers this scene:
The focus is on the shutdown / startup button just to the right of the heatsink, so the depth of field is maybe 25 mm front-to-back.
For comparison, the official 16 mm lens stopped down to f/8 has a tighter view with good depth of field:
It’d be nice to have a variable aperture, but it’s probably not worth the effort.
The Smell of Molten Projects in the Morning 