Intervelometer erratic behavior (interval vs exposure time)

[B.Rae]

First of all I'm glad to be here and glad to be trying out Magic Lantern on my Eos Rebel t3i (600D) for the first time.  So far I see many possibilities for this software and look forward to digging deeper into it's features as time progresses.  with that said I have recently become very interested in Bulb Ramping and downloaded version 2.3 but then realized there is a new Module called ETTR.  I began playing with it and at first it was taking pictures very erratically and not following the time I set for the intervalometer. 

It took me a while to realize that the interval needs to be added to the exposure length otherwise the camera immediately tries taking another picture while one is still being exposed... ie: if I have a 5 second interval with 30 second exposure it's no good. So for example it would need to be give or take 37 seconds to give me the 5 seconds I'm looking for plus the 2 second image preview.  With that said unless I'm missing something (and I read a ton of information about this last night but didn't find an answer)  it seems like the interval doesn't work how it would on a traditional wired intervalometer where that 5 seconds would be the time between exposures no mater what the exposure length was. 

Am I missing something here?  My hope is to work out a golden hour time lapse from day into night and move straight in to Milky Way time lapse (using ETTR Module) but as I understand it now I would have to set an extremely long interval in order to make it work once it's dark and that would not be ideal for the daylight portion of the timelapse.  Any info on a workflow would be appreciated. 


FYI I am running the following Nightly Build:

magiclantern-Nightly.2015Apr19.600D102.zip
Built on: 2015-04-18 17:59:10 -0700
Changeset: e08c6c0

Regards,


-B.Rae

[dmilligan]

There is a post along these lines about every week.

The ML intervalometer's interval period is the time from the start of one exposure to the start of the next. This is intentional. Most of the time it's the interval from one shot to the next that you want to remain constant NOT the interval between shots. That way the shutter speed can be adjusted without causing temporal jitter. If you keep the interval between shots constants, allowing the total interval to fluctuate with shutter speed, then you end up with a timelapse that has an erratic/uneven speed.

but as I understand it now I would have to set an extremely long interval in order to make it work once it's dark and that would not be ideal for the daylight portion of the timelapse.

I disagree. Why would you want nighttime to pass significantly faster than the daytime in your timelapse? I would argue that a constant speed is preferable in most all situations. Esp. in situations where there are objects with very constant motion (sun, moon, stars), that will appear to move at erratic speeds b/c you let your interval time change.

This is mostly just my opinion. So now with the scripting engine mostly working again, you can easily customize the intervalometer's behavior, or simply write your own, if you want to do things the way you are describing.

[B.Rae]

it's good point of view ... you got me thinking and I realize i had a fundamental misunderstanding of how the interval/shutter speed relationship works with the whole bulb ramping/ETTR feature.  Really if I'm shooting a time lapse of the sunset through into the dark hours with the interval set at a 30 or 40 seconds you figure it would be about 3 or 4 seconds of sunset for 25-30 seconds of milky way footage at 24fps which would simulate pretty well the last hour of the day and a good portion of the night sky with milky way.  My mistake was thinking of it more in a linear sense like the balance of screen time between the sunset and the milky way clips but for continuity I think you are right doing it the way I wanted to do would be slow through sunset and then suddenly the night sky would be flying by in the same amount of time give or take but at a much faster rate in time lapse terms.   Thanks for your time it makes more sense to me now... sometimes I just have to stick my neck out to learn something new

[dmilligan]

Here's an example I did. The interval time is a constant 45 seconds:
http://www.magiclantern.fm/forum/index.php?topic=12330