There has been lots of comments on taking off attachments, maintain Avatar Rendering Cost of 1 etc. so as to reduce lag. Here's a interesting article that dispells the myths of what cause lag.
Gogo from JuicyBomb wrote an article about how to light up one's av for photo taking without having to wear facelight. The instructions are very easy. I dont know whether it will work for me but I will definitely try them the next time I take a photo.