thats just coz he doesnt hav much experience mate i would still use the lense (depends on how good he is on the white beam mate) but try n get him a few clappers on the filter first so he knows wat the red beam is coz u think hes used ta the white light not the red now try him on a few clappers on the red light n hell will reconnise the red beam after a while soon as the dog knows the red beam u should reconise it when hes on the lead coz you should be able ta reconnise when the dog can see it by is recation of the dog mate atb