Loading multiple images from a folder, and Finding a specific one

Hi, I've been working for the last 10 days on this question, and getting nowhere.. what i am doing is studying how a flame starts and ends..thus i have 20 pictures, starting with a black one, and then the flame appears slowly and then disappears.. my job is to upload those images to matlab, and find an algorithmus that tells me when the flame started, and when did it end..

i would be really thankful for any help

[Daniel Shub]

What is your question?