This tamron af 70 300mm f4 56 di ld macro lens made for the nikon slr system incorporates a motor built into the lens itself which gives it the capability to autofocus with all nikon dslr cameras including the d40 and d40x in addition with the motor built into the lens focusing will be quieter and more responsive the 70 300mm di ld macro is a quality compact ultra tele zoom lens which covers the 70mm to 300mm telephoto range with a maximum magnification ratio of 12 at the tele end it