the box measurment

What is the purpose of finding the geometric center of a lens in relation to the major reference point (MRP)?

To ensure the lens is properly decentered when mounted in the frame.

What does the A dimension represent in the Box Measurement System?

The horizontal lens measurement.

What is the B dimension in lens measurements?

The vertical lens measurement.

What is the datum line also known as?

The 180-degree line.

How is the effective diameter (ED) of a lens determined?

By finding the longest distance from the geometric center to the edge of the lens shape and doubling that measurement.

What is the relationship between eye size (A) and effective diameter (ED) in a simple oval shape?

They are the same.

What does the angle (X) in the context of ED denote?

The angle at which the effective diameter crosses the datum line.

How is the minimum blank size (MBS) related to effective diameter (ED)?

The MBS is calculated using the effective diameter.

What does DBL stand for in frame measurements?

Distance between lenses.

How is the geometric center distance (GCD) calculated?

By adding the A measurement to the DBL.

What is the advantage of knowing the angle of the effective diameter (X) for surfacing labs?

It allows them to make the lens as thin as possible.

What is the significance of the distance between two boxed lenses in relation to the DBL?

It becomes the measured DBL and may not match the bridge size indicated on the frame.