Well, as I got two polaroid cameras, I did search what was the difference between their films. First of all, my 100 uses sx-70. This was the first kind of instant film for polaroids. When they did the 600 (that fits my Close-up) this was 4 times more sentitive. That means that if you take a photo with a sx-70 camera using a 600 film, it will be overexposed. the only way to solve it and take good photos, is when you change the filter, as the “Thoughts About Photograph” teach.