Hi folks! I'm an italian guy, so sorry for my BAD english! During the last summer I made some (short) timelapse and edited it with LRTimelapse.

I followed all the tutorials about how to make a timelapse with this software, and I founded it really useful, but I have an issue with a timelapse that I made during a sunset, you can see it here:

[Video: http://www.youtube.com/watch?feature=pla...Sv5b4LMMro]

As you can see, starting from 0:09 when the sun goes down it becomes smaller. So, since the brightness was starting to become really dark, I changed the exposure time (making it longer)...but, as result, the sun become bigger! And then, after some minutes, smaller again. And this process is repeated for 3/4 times.

I made this timelapse in manual mode, and I unlocked the lens and rotated it in order to reduce the flickering.

How can I avoid it in the future? Tell me if you need more info! Thank you to all that will answer to this thread!

This is because, the sun blows the highlights. The extend of that blowing will be bigger or smaller depending on the exposure.

Mesurements to reduce that:
1.) Adjust more frequently in smaller steps
2.) Underexpose even more and lighten up the shadows in post processing to prevent the highlights from blowing

Another option would be to not shoot directly towards the sun, leaving the sun out of the frame.

This is because, the sun blows the highlights. The extend of that blowing will be bigger or smaller depending on the exposure.

Mesurements to reduce that:
1.) Adjust more frequently in smaller steps
2.) Underexpose even more and lighten up the shadows in post processing to prevent the highlights from blowing

Another option would be to not shoot directly towards the sun, leaving the sun out of the frame.

Thank you for you reply! I will try the first option, because I already tried the second one, and lightening up the shadows too much created a noise in the images. Look at this timelapse to understand of what I'm talking about at 0:10 :
[Video: http://www.youtube.com/watch?v=VIo-kaKkFv0]

Underexposing is only necessary as long as the sun is visible. After it has gone, you can expose brighter again - always check the RBG histogram and take care not to blow the channels - especially Red on a Sunset.

After producing numerous sunset sequences with LRT this is the single greatest flaw in the process. Even with massive underexposure the sun is always going to clip the highlights (that's why its white). The best you can do is underexpose as much as possible (to minimise the clipped area surrounding the sun) and use smaller exposure adjustments.

If you do this the flashes become less noticeable and hopefully it wont result in an appreciable flicker in your sequences. No doubt with some work in after effects you could improve the situation further.

This is no flaw in the process - this is weakness in the dynamic range of the camera.
Like you said: Small Adjustments (1/3 stop), Underexpose, Pull down the lights in LR, LRT Plus Motion Blur when rendering.

Okay let me rephrase. It's a flaw in the concept based on the existing technology available. Since the process (LRTimelapse) and concept (the idea of matching different exposures by using RAW adjustments) are closely interlinked and we have no access to cameras of near infitinite dynamic range then you can understand why I might use the terms interchangeably.
There is no solution other than blub ramping or complex video editing work. Dont get me wrong I think that LRTimelapse is fantastic or I wouldnt be using it, but I do consider this to be a genuine issue (and one that you can't solve with your software so I don't criticise its design) albeit a very small issue.
As far as the video editing work goes, I tried this last night. There are a number of potential ways that you can blur frames together to make the flash less sudden. Since this blurring spoils the rest of the image you need to use masking to ensure the effect is only applied when it is needed.
It all depends how picky you are, personally I find if you do everything you can to tackle the problem then it becomes unnoticeable for anyone who isnt looking for it.