Humphreys 350 Lensometer

[EyeQ]

Hi,

We need some help.....

Our Humphreys 350 lensometer is constantly reading 0.25 diopters of prism, even when there's no lens. We don't have a manual, i was hoping someone could help us with some advice on resetting/ calibrating to zero.

Thank you.

[Barry Santini]

Try blowing off any dust on the sensor behind the lens stop.

B