Zoom lens having high variable magnification

A zoom lens having a high variable magnification in which first and second lens groups respectively having negative and positive focal lengths are sequentially arranged from an object side of the zoom lens to an image side thereof and a combined focal length of an entire lens system is changed by changing a distance between the first and second lens groups while the position of an image surface is constantly held,

• said zoom lens being constructed such that the second lens group is constructed by front and rear lens groups respectively having positive and negative focal lengths, and the respective focal lengths f.sub.1 and f.sub.2 of the first and second lens groups, the respective focal lengths f.sub.2 (F) and f.sub.2 (R) of the front and rear lens groups in the second lens group, and combined focal lengths f(W) and f(T) of the entire lens system at wide angle and telescopic ends thereof satisfy the following conditions,
• [f.sub.1 +f.sub.2 .multidot.{2-(f.sub.1 /f(W))-(f(W)/f.sub.1)}]/f(T)<0.6(I)
• [f.sub.1 +f.sub.2 .multidot.{2-(f.sub.1 /f(T))-(f(T)/f.sub.1)}]/f(T)<0.6(II)
• 0.6<.vertline.f.sub.2 (R).vertline./f.sub.2 (F)<6.0 (III)
• 0.8<f.sub.2 (F)/f.sub.2 <1.4 (IV)
• 0.5<.vertline.f.sub.1 .vertline./.sqroot.[f(W).multidot.f(T)]<1.3(V)
• where .sqroot.[] means a square root of a value within bracket [].