Addmen OMR Scanner Software correctly reads even rotated, skewed or distorted OMR sheets. But we should keep the sheet holding brackets of the document feeder pocket in the sheet scanner properly close; in order to avoid the OMR sheet from straying and prevent it from tangling or unnecessarily tilting in the scanner.
DO NOT increase brightness or contrast unless guided. Scan at default settings.
Keep the scanning area wide enough so that the time line or 4 corner index points are properly scanned and there is sufficient white space outside them.
For scanning of B/w OMR answer sheets, preferably scan as B/w (1-Bit) image. Avoid scanning as B/W Photo (Gray scale) or Colour Photo (RGB) to keep file size minimum.
For sheets with 2 colour printing or sheets with photograph pasted on them, preferably scan as colour (RGB) image. Avoid scanning as B/W (1-Bit) or Gray scale to keep photo clear.
For Sheets containing OCR, Barcode, Photograph scan at minimum 150 DPI.
Save as JPG, TIFF or BMP file only. DO NOT save as DOC/PDF.
If you are using TIFF Format for saving as TIFF (Single File) which creates one file for one scanned image. Remember, we need to have separate scanned image files for each OMR Sheet. So do not use Multi page TIFF that inserts all the scanned images onto different layers of a single image file.
Some models of scanner are not able to scan pencil marks properly and deliver an image with rarified impressions of the bubbles. This rarified impression is formed due to effect of glare because of the angle of incidence of light from the scanner. So if the scanner itself has not captured the pencil mark properly, then the input for the software is already inappropriate and hence will have its impact on accuracy. It is to be remembered that the software reads the image, not the paper. So if the scanner has not detected the mark and formed the image properly then the software will read what is there on the image irrespective of what was there on the paper.
Some pieces of scanners, as the get old and the drag roller gets weary, start to affect the dimensions of image. Due to irregular drag of the roller sometimes the scanner delivers skewed or distorted images. The OMR software has allowance to accept skew or distortion within a certain limit as per the settings but if this distortion becomes excessive and uneven throughout the image then the scanner must be repaired or replaced.
Some scanners have wobbling rollers due to which even if the final dimension of the image is ok still the image is stretched from within such that along the length certain portion of the length is smaller than the actual length of the design while some portion of the length is stretched long. These possible issues are not covered in the scanning guide because it is not related to working instructions for the user. Even though the user might be doing everything correctly as guided, still the properties or defects of the scanner might be negatively affecting the output. If these issues are noticed, it might be required to repair or replace the scanner. Such cases can be easily identified by scanning the same sheet on a different scanner and comparing the image or output.