Fixed focal length lens and image pickup apparatus

A fixed focal length lens comprising, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power and a fourth lens unit, the second lens unit and the third lens unit moving for focusing differently from each other to change a distance between each pair of adjacent lens units, wherein

• conditional expressions:
• 3.3<f1/f<12.8, and
• 0.0<f3/f2<0.5
• are satisfied where f represents a focal length of the fixed focal length lens in a case of focusing on an object at infinity, f1 represents a focal length of the first lens unit, f2 represents a focal length of the second lens unit and f3 represents a focal length of the third lens unit.

An image pickup apparatus comprising:

• a fixed focal length lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power and a third lens unit having a positive refractive power, the second lens unit and the third lens unit moving for focusing differently from each other to change a distance between each pair of adjacent lens units, wherein
• the first lens unit includes, in order from the object side to the image side, a first lens having a negative refractive power and a second lens having a negative refractive power, and
• conditional expressions
• 3.3<f1/f<12.8, and
• 0.0<f3/f2<0.5
• are satisfied where f represents a focal length of the fixed focal length lens in a case of focusing on an object at infinity, f1 represents a focal length of the first lens unit, f2 represents a focal length of the second lens unit and f3 represents a focal length of the third lens unit;
• and
• an image pickup element arranged on an image plane of the fixed focal length lens.

An image pickup apparatus comprising:

• a fixed focal length lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power and a fourth lens unit, the second lens unit and the third lens unit moving for focusing differently from each other to change a distance between each pair of adjacent lens units, wherein
• conditional expressions
• 3.3<f1/f<12.8, and
• 0.0<f3/f2<0.5
• are satisfied where f represents a focal length of the fixed focal length lens in a case of focusing on an object at infinity, f1 represents a focal length of the first lens unit, f2 represents a focal length of the second lens unit and f3 represents a focal length of the third lens unit;
• and
• an image pickup element arranged on an image plane of the fixed focal length lens.