Compact zoom lens

A compact zoom lens comprising:

• a first group having a positive refractive power, including a cemented positive lens of a negative lens and a positive lens, and a positive lens, and movable for focusing;
• a second group having a negative refractive power, comprising a negative lens and a cemented negative lens of a negative lens and a positive lens, and movable for variation of magnification;
• a third group having a positive refractive power, comprising a cemented positive lens of a positive lens and a negative lens, and movable for compensation along with the second group;
• and
• an image forming lens having a positive refractive power, positioned to the rear of the third group on an optical axis, and consisting of fourth and fifth groups,
• said fourth group including, from front to rear, at least one positive lens with its front surface covex toward the front, and a negative lens;
• and
• said fifth group consisting of, from front to rear, a negative meniscus lens of rearward convexity, and a positive lens,
• said zoom lens satisfying the following conditions:
• 0.7<.phi.4,5/.phi.4<0.85 (1)
• 1. 5<.phi.4s/.phi.4,5<2.2 (2)
• N4n>N4p (3)
• 1.76<N5n<1.85 (4)
• 30<.nu.5p<45 (5)
• where
• .phi.4 is the refractive power of said fourth group;
• .phi.4,5 is the overall refractive power of said fourth and fifth groups;
• .phi.4s is the refractive power of the first surface of the positive lens of said fourth group;
• N4p is the refractive index of the positive lens in said fourth group (when the positive lens is plural in number, the average value thereof);
• N4n is the refractive index of the negative lens in said fourth group;
• N5n is the refractive index of the negative lens in said fifth group;
• and
• .nu.5p is the Abbe number of the positive lens of said fifth group.