Umpires can offer batsmen the option to go off for bad light if conditions become dangerous. Modern floodlights have reduced bad light interruptions.
Details
Bad light rules apply primarily in Test cricket. When light deteriorates to a level where umpires consider it dangerous for batsmen (particularly against pace bowling), they can:
1. Offer the batsmen the light — the batting team can choose to come off or continue 2. Take the players off if conditions are truly dangerous — even if the batting team wants to continue
Once play is stopped for bad light, it can only resume if the light improves to the level it was at when play was stopped.
The introduction of floodlights in many Test venues has reduced bad light interruptions. However, umpires may still offer the light if the natural conditions are too dark, even with floodlights available.
Bad light rules don't apply in the same way in day-night Tests or LOIs played under lights, as artificial lighting is designed to maintain adequate visibility.
Historical Evolution
Bad light has been a contentious issue throughout cricket history. Many crucial Test matches have been affected by bad light stoppages. The Edgbaston 2005 Ashes Test saw play continue in very dark conditions as Australia tried to save the match, leading to debates about consistency.
The ICC modified the rules in 2013 to give umpires more power to keep play going, but safety remains the overriding concern.
Current Rule
Umpires assess light levels using a light meter. Can offer batsmen the light or suspend play if dangerous. Floodlights used where available.