Image forming apparatus and control program of image forming apparatus

An image forming method for forming images with an image forming apparatus for simultaneously conducting multiple lines of exposure by scanning multiple laser beams from multiple light sources onto an image carrier in a main scanning direction, the method comprising the steps of:

• executing an image forming mode by selecting out of two types of image forming modes of a first image forming mode where an image is formed at a first image forming speed by using all the multiple light sources, and a second image forming mode where the image is formed without using at least one of the multiple light sources at a second image forming speed slower than the first image forming speed;
• and
• allowing a light source, which is not used in the second image forming mode, to emit a laser beam onto outside of an image area where the image is formed based on the image data.

A computer-readable storage medium stored therein a program for a computer of an image forming apparatus for simultaneously conducting multiple lines of exposure by scanning multiple laser beams from multiple light sources onto an image carrier in a main scanning direction, the program allowing the computer to execute the steps of:

• executing an image forming mode by selecting out of two types of image forming modes of a first image forming mode where an image is formed at a first image forming speed by using all the multiple light sources, and a second image forming mode where the image is formed without using at least one of the multiple light sources at a second image forming speed slower than the first image forming speed;
• and
• allowing a light source, which is not used in the second image forming mode, to emit a laser beam onto outside of an image area where the image is formed based on the image data.