If you go looking for a LED flashlight at a store like Home Depot or Walmart look for the LUMES rating. Most posts I have seen on the forum say anything over 140 lumes. I recently bought a light on Amazon that was 200 lumes and I can see the chick moving inside the shell in my darkened bathroom just off the kitchen where I have my incubator.
I agree with andalusn, find a LED flashlight with as many lumens as possible. I also learned a trick from another BYC'er. Put your egg on you candler that you made with the air cell up and then shine a mag light through the end with the air cell so you are shining light into the egg from both ends. Works pretty good.