One major drawback of the A-model was the limited range at which the TV-seeker could lock on: although the missile has a range of up to 7nm (13km) under the worst possible circumstances (a low and slow aircraft), attenuation at optical wavelengths limits lock-on range to about 3nm (5.5km). Furthermore, the AGM-65A needs 4-8 seconds to lock on, which is an eternity on the modern battlefield.
This is the citation from this Falcon4.0 page:
http://www.f-16.net/f-16_armament_article4.html
This is for A version
The AGM-65K missiles should be an updated derivative of AGM-65G. G's guidance section would be replaced with a 480x480 pixels CCD-TV sensor, the same used in H models, plus modern hardware and software. CCD-TV sensor will provide mainly clearer picture and longer standoff range.