Nightscape TIme Lapse flicker Question

[Stonius]

Hi All,

I made a Nightscape over New Years and there is something bugging me. Here's the video for reference (5.6MB)

http://www.markusstone.com/hosted_files/LMDSS_Crux.mp4

There is a seemingly random flicker.

I know it's a pretty common thing in Time-Lapse, but I'm struggling to determine the cause. The strange thing seems to be that only the SKY changes exposure. The ground in the FG stays relatively constant. How can this be?


The camera was in Manual mode
The ISO, Shutter Speed and F stop were constant (I didn't touch it and the metadata says the same)
The interval timer I was using was MagicLantern (internal open source software) Maybe that's it?
Canon 5D Mkii w Sigma Art 24mm
Shutter Lock up was on


Possible issues I've thought of are that maybe the ground, being darker, is on the tail end of a bell curve of exposure, so when the Sky jumps by a stop and a half, the ground jumps to a much smaller degree and therefore seems to be relatively unaffected? Ie the sky doubles from say 30% to 60%, while the ground at say, 1% only goes to 2%.

I heard that the lenses nowadays reset the Iris diaphragm after each shot which can cause issues for time lapse if it doesn't reset to exactly the same spot. But this is a big variation and the lens is not cheap. I'd be suprised.

Maybe a shutter issue with the camera? The Mkii is getting on a bit. Maybe the shutter is sticking or taking a little longer? Maybe the portrait orientation of the camera is not good for the shutter, making it work against gravity?

Something Screwy with the metadata? Maybe changing it so that the default version of the program is actually tweaked in a random way - which would point to a file writing to card issue, and possibly a magic lantern issue as well.

I have another series that I shot thanks to much help from this group, of Orion. It was using my 50mm lens. There are no flicker issues with that one. Hmmmmmm

Markus

[h0ughy]

sky conditions do change throughout the night?

[Stonius]

I guess they might, but I saw no cloud/haze on the night, or in photographs. And I can't think of anything that would make the entire milky way go 1.5 stops darker in under 10 seconds. Strange...

Markus

[Redshift13]

A white balance issue?
Even minute variations in ambient light (not noticeable to naked eye) can cause white balance changes in-camera - this is most noticeable when WB is set to auto.
If not white balance, then my money's on some setting in ML that's causing the grief (I've not experimented with ML enough to guess what setting that might be :shrug: ).

[pluto]

How are you processing the images before compiling them into a vid?
Are you shooting raws?

As Rohan said, it could be a white balance issue, especially if you shot it on auto WB. I shoot all my timelapses on auto WB but then I always apply the same white balance settings (custom WB values) to all the raws when I export them out of Lightroom before I turn them into a vid.

I used to do heaps of timelapses with my 5DmkII and ML and never had a problem (I miss ML now that I'm on a Sony :()

Doesn't look like iris flicker to me as it's not really a flicker more like something is changing at a few points throughout.

[Bassnut]

If you go through it a frame at a time, the flaring occurs exactly at the same time red lights are exposed (lap top screen?) and torches. Given the camera was in manual, perhaps the flaring occured in post?.

[sil]

looks like a white balance issue to me. try locking it off to daylight. otherwise an auto setting you missed or in your RAW software processing.

[Stonius]

Hmm. I didn't explicitly set the white balance. Probably because I figure being RAW images, it would be easy to change in post, so it wasn't that important.

But looking at it now, the metadata tells me that it was manual.

I'm still going through it and trouble shooting. I'll repost here if I find out what's going on so others with the same issue may find a fix here.

Thanks for the suggestions so far.

Markus

[sil]

If i hadnt read the thread first my reaction would have been its reacting to the change in exposure of the milky way as it moves. But this should be reflected i the metadata (which is not the problem , its accurate). But if you have locked off iso, shutter speed, f stop , WB, focus, etc with the camera it will NOT show such changes unless there IS some auto feature somewhere still enabled. That leaves the processing of the RAW files. Exposure compensation? As the milky way brightens then lighter ground objects dim slightly, which is why it feels like its an exposure issue and once you've set your exposure triangle all the camera has left is its trickery, like exposure compensation, noise reduction, low light noise reduction. just go through camera menu settings, look for things that sound like they make their own changes... words like Reduction and Compensation and Auto and Sensitivity.

BTW do you shoot only RAW or RAW+JPG? if you shoot RAW + JPG then timelapse the JPGs and if they are flickery the problem is with the camera but if it goes away its definately your RAW processing on computer. Certainly a way to test.

[Stonius]

Well, I went back into Adobe Bridge and selected all frames and took them into raw, selected all frames again and set them all to default (as shot).

Same issues in all the same places. I'm starting to think that maybe it's the timer I used. Magic lantern is widely used, but it is open source. Perhaps there's a bug where the shutter was open for longer than the 10 second exposure, but it was still reporting the metadata as 10 seconds.

I did another series, same night, different lens (50mm Sigma Art), which worked fine. Which is useful for this series from the point of view of troubleshooting.

Thinking about it, I was exposing for 10 seconds with a 5 second cool down between frames. Maybe Magic Lantern started exposing for the full 15 second cycle, which would cause a brightness jump of the kind of magnitude I'm looking at here.

Also, I swapped out the CF card right before this series. Each card has a little copy of the operating system on it. Maybe the OS on that particular card has been a little bit corrupted.

So variables I will test are;
Refresh OS on card / use a different card
Use different (external) interval timer
See if it only occurs with the 24mm lens

I'll let you know how I go :-)

Thanks

Markus

[Redshift13]

I agree, one/some of the ML files on the card you used could be corrupted/missing, so refreshing the ML files is a good idea.
Alternatively, could the version of ML on the card you used be either not up-to-date or for a different model camera (again, refreshing the ML files would identify this)?
Also, just an FYI as I have a 600D (so using a different model camera), but I have not noticed any intervalometer issues after nearly 4 years of use of ML & this is mostly what I use ML for, don't use many other features at all (wish I had the time to learn them!).

Good luck with your trouble shooting and keep us informed of your findings.

[sil]

I'm a Nikon shooter so no experience with MagicLantern. But my experience with intervalometers (in camera, software and remote control based) is a problem when it comes to trying to maximise exposure numbers in a given timeframe. They can trip up and "get confused". leading to inconsitent intervals and other problems. Especially getting delays and intervals and exposure times balanced so the gear has time to write the shots to card before its all ready to take the next shot. They just never seem to work as you'd expect and i've ditched using them altogether for an alternate method to get the same results.

[pluto]

Markus, I'm really interested to have a look at these files, would you be able to upload some of the raws so I can take a look?
Just about 10-20 files around one of the really bright spots - about a second into that vid.