Assertion: eyepiece's field | /r/CapableOf | exceed 28 millimeters
Facets:
value: sometimes
type: TEMPORAL
value: with modern plan apochromats
type: OTHER
Source sentences:
text: In early microscope objectives, the maximum usable field diameter tended to be about 18 millimeters or considerably less, but with modern plan apochromats and other specialized flat-field objectives, the maximum usable field can sometimes exceed 28 millimeters.