It looks like you are using an ad blocker. That's okay. Who doesn't? But without advertising revenue, we can't keep making this site awesome. Click the link below for instructions on disabling adblock.
Welcome to the Newschoolers forums! You may read the forums as a guest, however you must be a registered member to post.
Register to become a member today!
That happens because the aperture is not exactly the same for every picture, it slightly changes even though you always have it on the same setting.
To correct that in post production use the program called LTimlapse (or something like that).
To prevent it for happening again do the following, when your settings for the timelapse are ready juste take a picture so that the aperture goes to the value you gave it and then unscrew the lens only a little bit so no contact between the camera and the lens can be made. This will keep the aperture open at the exact same value for all your timelapse. But it only works for Canon mounts.
I use fully manual lenses for timelapses for this reason alone. Never fails in that situation.
That said, if you're shooting a sunset/sunrise situation, it's better to just go with aperture priority and then deflicker it in post so that you have an even exposure..