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Unexpected exposure changes in RAW sequence
http://forum.timescapes.org/phpBB3/viewtopic.php?f=33&t=11060
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Author:  Charlayeur [ Thu Sep 26, 2013 3:11 am ]
Post subject:  Unexpected exposure changes in RAW sequence

Hi,
I am a newbie in timelapse. I recently shot a sequence of images in RAW format, with a Nikon D600. That was a sunny day with some clouds. And I shot a statue with the sun hidden behind the statue.
Manual Mode - Aperture : 16 - shutter speed : 125 - WB set to sunlight
The result is a sequence of images with sometimes good exposure (as the images i shot before as a test) and sometimes, but irregularly, overexposed images.
Here is a screencap of the first images of the sequence :
[flickr]http://www.flickr.com/photos/83823472@N02/9948538956/[/flickr]

I can't find out where this problem comes from. I read that shutter speed over 100 should be avoided. Could the 125 shutter speed be the real problem ? Or could that come from something else i've missed/done wrong.
Also, my ND filter is not a very high quality one.

Any ideas ?
Thanks for your help.

Author:  Charlayeur [ Thu Sep 26, 2013 8:02 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

I forgot to mention that the interval was 3 seconds.

Author:  oneLapse [ Thu Sep 26, 2013 8:11 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

Image doesnt work and the link doesnt bring me anywhere anyways. sounds like aperture flicker. since your on Nikon, the only thing I know of that you can do it to put the lens wide open and get more ND filters.

Also put it in LRTimelapse and run a deflicker.

really thought, its hard to tell when you didn't post the resulting video.

Author:  Charlayeur [ Thu Sep 26, 2013 8:48 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

Thanks for the quick answer. I will follow your advice.
I attached the missing image (from the broken link on my first post), just in case.

Image

Author:  pixelbot [ Thu Sep 26, 2013 9:15 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

that doesn't look like aperture flicker - it looks like something auto is going on here - have you looked at the EXIF for a couple of those files (like for DSC_8417, DSC_8418 and DSC_8419) it may be a combination of the aperture and the shutter flicker - having too fast of a shutter can lead to flicker also, as the actual difference between the shutter speed can lead to slight exposure difference that are magnified at faster shutter speeds (hope that makes sense)

timt

Author:  Charlayeur [ Mon Sep 30, 2013 2:29 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

I checked the EXIF and there are no changes in the aperture or shutter flickr.
The problem might be the shutter speed. I'll make some new tests to make sure.
Thanks for your answer.

Author:  Charlayeur [ Mon Oct 07, 2013 2:48 am ]
Post subject:  Re: Unexpected exposure changes in RAW sequence

Hi, just to let you know that I made some new tests, and solved my problem.

Test 1 : f8 - shutter speed 1/200 - no ND filter - ISO 200 - 350 images
Result : same problem, some images over exposed (more at the beginning of the sequence)

Test 2 : f18 - shutter speed 1/100 - no ND filter - ISO 200 - 350 images
Result : almost perfect, only one image is over exposed at the very beginning of the sequence.

Conclusion : that's definitely a shutter speed issue.
Thanks for the help.

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