Arducam Motorized Focus Camera: Depth of Field

According to the Arducam doc, their Motorized Focus Camera has a 54°×41° field of view, (roughly) equivalent to an old-school wide(-ish) angle 35 mm lens on a 35 mm still camera. For my simple purposes, the camera will be focused on objects within maybe 200 mm:

Arducam Motorized Focus Camera - desktop test range
Arducam Motorized Focus Camera – desktop test range

The numeric keys are 6.36 mm = ¼ inch tall, the function keys are 5.3 mm tall, and the rows are 10 to 11 mm apart.

The focusing equation converting distance to lens DAC values depends critically on my crude measurements, so the focus distance accuracy isn’t spot on. Bonus: there’s plenty of room for discussion about where the zero origin should be, but given the tune-for-best-picture nature of focusing, it’s good enough.

I set the CANCEL legend at 50 mm and it’s in good focus with the lens set to that distance:

Arducam Motorized Focus Camera - 50 mm
Arducam Motorized Focus Camera – 50 mm

Focusing at 55 mm sharpens the ON key legend, while the CANCEL legend remains reasonably crisp:

Arducam Motorized Focus Camera - 55 mm
Arducam Motorized Focus Camera – 55 mm

Adding another 5 mm to focus at 60 mm near the front of the second row shows the DoF is maybe 15 mm total:

Arducam Motorized Focus Camera - 60 mm
Arducam Motorized Focus Camera – 60 mm

Focusing at 65 mm, near the middle of the second row, softens the first and fourth rows. Both of the middle two rows seem OK, making the DoF about 20 mm overall:

Arducam Motorized Focus Camera - 65 mm
Arducam Motorized Focus Camera – 65 mm

Jumping to 100 mm, near the top of the first function row:

Arducam Motorized Focus Camera - 100 mm
Arducam Motorized Focus Camera – 100 mm

At 150 mm, about the top of the far row just under the display:

Arducam Motorized Focus Camera - 150 mm
Arducam Motorized Focus Camera – 150 mm

I think 200 mm may be the far limit of useful detail for a 5 MP camera:

Arducam Motorized Focus Camera - 200 mm
Arducam Motorized Focus Camera – 200 mm

At 300 mm the DoF includes the mug at 600 mm, but the calculator keyboard is uselessly fuzzy:

Arducam Motorized Focus Camera - 300 mm
Arducam Motorized Focus Camera – 300 mm

At 500 mm, the mug becomes as crisp as it’ll get and the text on the box at 750 mm is entirely legible:

Arducam Motorized Focus Camera - 500 mm
Arducam Motorized Focus Camera – 500 mm

At 1000 mm, which is basically the edge of the desk all this junk sits atop, the mug and text become slightly fuzzy, so the DoF doesn’t quite reach them:

Arducam Motorized Focus Camera - 1000 mm
Arducam Motorized Focus Camera – 1000 mm

I limited the focus range to 1500 mm, which doesn’t much change the results:

Arducam Motorized Focus Camera - 1500 mm
Arducam Motorized Focus Camera – 1500 mm

I could focus-stack a set of still images along the entire range to get one of those unnatural everything-in-focus pictures.