i'm no expert but I'll share what I know. it would be a combination of many things, generally a shutter speed slower than 1/60th of a second allows for movement in either the camera or the subject and results in a blurry pic unless your on a tripod and have a still subject. You photographers out there let me know if I'm backwards on this but for low light situations you can use a higher iso film setting so it exposes faster, and use a low aperture setting to let in the most light.