If finddead=Y, embadpixfind looks for too dark pixels, rows and columns using the same algorithm (but reversed to look for holes). The statistics in a single observation is usually not enough to find any dark pixel, but dark rows or columns may be found. The maxratio parameter avoids detecting 'grey' pixels, rows or columns on observations with high statistics.
Whatever findbright, the very bright pixels (found at probathreshold squared) are looked for first (some are so bright that they can disrupt the more subtle row and column searches). If both findbright=Y and finddead=Y, dark and bright columns and rows are searched for together in order of decreasing significance (either positive or negative). This avoids finding too easily bright columns/rows next to very dark ones, and vice-versa.