I sometimes see “crescent effects” under the microscope with the Oris™ Detection Mask in place. Is this a problem for quantification using a microplate reader?

The mask provided with the Oris™ assays has an aperture diameter of 2.1 mm while the size of the Detection Zone formed by the stopper is 2.0 mm. The larger mask aperture is designed to allow some fluorescent background signal to included in the light path in order to bring the detector into the appropriate dynamic range, as illustrated in this technical note.