OMR sheet is not the ordinary paper. It is a paper with a technical format which is further undergoes some technical processing. It consists measured dimensions and parameters which have a concern with the OMR sheet reading software to check the bubbles and deliver OMR test results accurately.
In fact the Addmen OMR Reader Software is very adaptable and permits varieties in identifying filled marks, yet it absolutely depends on upon the Examination body whether to follow strict rules or rules with less restrictions.
If you mark the OMR bubbles with pencil or blue/black ball pen or blue/black gel pen the OMR marks will be read by the Addmen OMR test reader software;
If you fill complete bubbles or even if you leave the bubble slightly unfilled or improperly filled, still the Addmen OMR Answer Sheet Checker will read the OMR Answer sheet properly;
If you slightly overfill or spill by mistake while filling the OMR circles, it will still be read accurately by the Addmen OMR test answer sheet checker;
If you use whitener in the OMR answer sheet, technically it is not a problem and Addmen OMR checking software can still read accurately;