ASTM D7298 Measurement of Comparative Legibility by Means of Polarizing Filter Instrumentation

Scope:

ASTM D7298 test method gives an objective way to compare the ease with which printed information such as in product labeling can be read. This test method compares the legibility of a printed item to that of other objects rather than assessing it against a standard.

Procedure:

In ASTM D7298, the specimen is adjusted with a moveable stage using the hand crank. The subject’s visual acuity is recorded and measured using a near distance visual acuity card with the Snellen visual acuity scale followed by the subject’s gender and age. A rheostat is used to adjust the light level inside the instrument to 25 ± 1 fc. The training reference is placed on the easel, the reference should not be curled and should be flat against the easel. The subject has to put on any eyewear they regularly use to read package labels and stare into the eye shield. The subject’s use of corrective eyewear will be documented. The subject is instructed to rotate the handwheel counterclockwise “to the first point at which the subject can clearly see printed matter without straining their eyes,”. The subject’s legibility index and the degrees of rotation necessary should be noted. 

Specimen size: 

ASTM D7289 test method is developed using subjects of ages 19 to 28 years. It is advised that subjects aged 19 to 28 be used in cases where variability needs to be kept to a minimum.

Results:

ASTM D7289 test report should contain the following information: age range, legibility index, standard deviation, test location, test date, time of day, gender, use of eyewear, and type of eyewear.

Conclusion: 

ASTM D7298 test method defines a standard technique for assessing the comparative legibility of printed matter under consistent, controlled light conditions using a specialized instrument