Card title: Enter a title to identify this card - your name and the name of your lens maybe? Enter a space to leave it blank.
Eye offset: Measure the distance between the centers of your eyes in cm.
Arm length: Extend your arm holding a card vertically between your thumb and forefinger. Measure the distance in cm between your eye and the card.
Focus distances: A comma separated list of distances you want for rangefinder scale. These should coincide with the scale on your lens. Infinity will be added automatically. Distances shorter than your arm will not work.
Distance units: Enter the units used for the distances on your lens
Focal length: Enter the focal length of your lens in mm.
Maximum aperture Enter the widest (smallest no.) aperture of your lens.
Minimum aperture Enter the narrowest (largest no.) aperture of your lens.
Film size: Select your film size: Minox, 110, 135 (35mm), etc.
CoC: Optionally, you may enter a custom circle of confusion in mm if you don't want to use the d/1500 values for common film sizes from above.

Note: This will generate a pdf which should be printed at 100% magnification. The final card should be 3.5" wide by 2" tall. These are the dimensions of a standard business card. You will have to print it from an application that lets you set the size of the image you are printing.

To Use: Hold the card in your hand at arm's length. With your left eye, line up the '0' marking with a vertical element of the object you wish to measure the distance to. Now look through your right eye. The distance measurement that lines up while looking through your right eye is the one you want.