2 problems with Time Lapse

[Akkasi]

Hi guys,

I've recently dug into doing time lapse shots (5 second intervals) of the clouds and I've encountered two main problems:

1) the clouds look grainy. I'm using 55-250mm lens on Canon 60D.
2) there seems to be a flash of light every few frames or so. I'm assuming this is some sort of auto function but can't figure out which. I'm using Manual mode btw.

Any ideas how I can sort these out?

Thanks!

 

[gridlock]

What shutter speed and aperture are you using? Have you set a fixed ISO?

Post examples of normal and light frames with EXIF data here if you still have the problem