Why would anyone want to disable the AF assist light? You are probably wondering if my mind has gone off the edge. After all, the camera companies spent millions of dollars and man-years developing a method to auto-focus better in low-light situations. The AF assist light is a wonderful feature that the marketing department list in their camera brochures.
It is true, the AF assist light is a great asset to have on a camera for still-life or modeling shots in low-light situations. But can you imaging the AF assist light beaming on and off during a play or during candid shots at a party? During these situations the AF assist light can be an annoying distraction.
I shoot quite a bit of people and wildlife grab shots. Therefore, when I got my Canon Elan IIe camera, the first thing I did was disabling the AF assist light using the built-in custom functions. However, there are plenty of cameras out there that do not provide the capability to disable the feature. I have three such cameras: the Canon IX, Canon Rebel G, and the Olympus C-2500L.
One very easy way to disable the AF assist light is to turn off AF and use manual focus instead. Unless you are an old school MF type of a person, this option does not sound tempting at all. Personally, I hate using MF unless I am in situations where AF does not work. In many low-light situations, the AF still works, just a little bit slower.
With the Rebel G, I uncovered another method that seems quite useful. Simply wrap the strap over the top of the camera and in front of the AF assist lamp. This effectively eliminates the beam. However, it will not work if you rather have the strap around your neck. And I seriously advice having some kind of secondary hold on the camera at all times. In this case, the battery grip with the hand strap comes in handy.
Another method to disabling the AF assist light without disabling the AF function is to tape over the AF assist lamp using electrical tape. The electrical tape prevents light being cast on the subject and prevents back-lighting the tape. The subject and spectators will never realize the AF assist light is lit.
At the end of the event, remove the tape. Do not leave the tape on for more than a day or two. The tape may leave residues if left on for prolonged period of time. I have shot quite a few occasions successfully using these methods.