- Open the Adjust Image window by going to Process > Adjust Image.
- Move the cursor around the parts of the image you know you want to be displayed as white. Set the maximum brightness to be around that value. You can move the sliders, or just type a number into the box and hit enter. All pixel values at that number or above will be displayed as white.
- Move the cursor around the areas of the image that you would like to be displayed as black, and set the minimum value to a number in that range. Again, you may use the sliders, or type in a number and press enter. All values below that number will be displayed on the screen as black.
- All values between the numbers you set will be displayed as shades of grey.