The pentax af 540 fgz ii flashgun is an auto flash unit for pentax dslr cameras this portable flash unit features a guide number of 54 at iso 100m and a wear resistant construction on front of af 540 flashgun is a fixed led light which comes in handy for close distance movie recording and still image shooting user can customise flash operation by pre setting as many as nine different flash functions to ir preference including onoff of catch light function using led light and opt