When your monitor is properly adjusted, you will see 7 / 11 / 15 / 23 / 26 distinct zones in the images around from pure black to pure white. If you do not now see all 7 - 26 zones, use your monitor's contrast and brightness controls to make any necessary adjustments. Consult your owner's manual if you do not know the location of these controls. Alternatively, you can use the monitor calibration modules which are built into Photoshop and some other software.