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 GBTimelapse questions 
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Joined: Tue Feb 03, 2015 3:40 pm
Posts: 7
Post GBTimelapse questions
Long time lurker, first time poster so hi everyone!

I do a bit of time lapse recreationally and professionally but to date it has been pretty basic stuff. I've done a few longer scale corporate day to night lapses spanning a week or two but the challenge with them has been largely related to storage space, battery and shutter life - burned through two shutter last month :/ (For trivia's sake at 160k and 8k retrospectively on a T3i). I do have a job coming up that requires some pretty speccy, precise time lapsing though, so I've been researching a few holy grail methods.

I settled on the GBTimelapse package, due to the shear power and flexibility of its functionality. It's pretty amazing. A few nights of intensive video watching and testing later I'm left with a pretty simple question: which method should I use to get a clean holy grail time lapse?

To elaborate, the challenges I'm facing are:
* Using shutter speeds faster than a second introduce flicker
* Using aperture stops higher than full open introduce flicker
* Removing an ND mid-lapse causes a sizable vignetting and colour cast shift

Given ideally I should be using a wide open f-stop at slow shutter speeds is there a trick to juggling the exposure reciprocity triangle? I'd rather not use an ND due to my limited ability to correct the shift. I know the right value of settings are hidden away there somewhere, I just can't seem to crack them! I don't have GBDeflicker but I guess I could pony up for it if necessary, although I was hoping GBTimelapse would remove the need for a deflicker package. I have MSU Deflicker if need be.

The scenario's I'd be shooting are night to day and vice versa of city and beachscapes. How do other people approach these types of shots with GBTimelapse?

Thanks for reading.


Tue Feb 03, 2015 4:03 pm
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Joined: Thu Feb 18, 2010 4:47 am
Posts: 388
Location: St Gallen, Switzerland
Post Re: GBTimelapse questions
Quote:
* Using shutter speeds faster than a second introduce flicker


Do bulb ramping with an external device that is not limited by the vagaries of Windows in your laptop. Possibilities: Dynamic Perception`s MX2 or MX3 or Emotimo`s TB3. I`m sure there are others. A second hand MX2 would be a cheap way to do it.

Quote:
* Using aperture stops higher than full open introduce flicker


Unless you employ the Canon lens twist trick. Press the depth of field preview lever and untwist. The aperture stays put and so no flicker.

Quote:
* Removing an ND mid-lapse causes a sizable vignetting and colour cast shift


The maker of GBT, Mike Posehn, seems to have managed it with a certain Hoya filter I think. But most others do cause a vignette and colour jump, you`re right. For a full "Holy Grail" transition without ND filter you`d need to ramp a declicked lens with a lens motor. Mike does that with his Emotimo TB3.


Wed Feb 04, 2015 1:02 am
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Joined: Tue Feb 03, 2015 3:40 pm
Posts: 7
Post Re: GBTimelapse questions
Ian wrote:
Do bulb ramping with an external device that is not limited by the vagaries of Windows in your laptop. Possibilities: Dynamic Perception`s MX2 or MX3 or Emotimo`s TB3. I`m sure there are others. A second hand MX2 would be a cheap way to do it.


Thanks for the tip. I have an MX3 controller and was going to try that method next. Good to know it'll help!

Quote:
Unless you employ the Canon lens twist trick. Press the depth of field preview lever and untwist. The aperture stays put and so no flicker.


I've found locking the aperture via the lens twist method makes a huge difference in reducing (though no completely removing) the flicker.

Quote:
The maker of GBT, Mike Posehn, seems to have managed it with a certain Hoya filter I think. But most others do cause a vignette and colour jump, you`re right. For a full "Holy Grail" transition without ND filter you`d need to ramp a declicked lens with a lens motor. Mike does that with his Emotimo TB3.


Interesting. I wonder if it was the Hoya ND400 filter? I have the Kenko branded version of that filter but haven't been able to correct the shift in saturation and vignetting.

Thanks for the response and the tips. I'll boot up the MX3 and give it a try. Aperture lock with a limited ISO range greatly reduces flicker but hopefully adding the controller into the mix will remove the remaining flicker.


Wed Feb 04, 2015 2:39 pm
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Joined: Thu Mar 10, 2011 11:38 pm
Posts: 585
Location: Exmouth, Western Australia
Post Re: GBTimelapse questions
Look at LRTimelapse software for an affordable flicker-removing package. To remove aperture flicker at source, assuming you are using a Canon camera, you can use either Nikon or Pentax mount lenses via a simple adapter. Buy a lens with a manual aperture ring and a cheap adapter that does not allow the camera to open the iris between frames.

Kit


Thu Feb 05, 2015 2:28 am
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Joined: Tue Feb 03, 2015 3:40 pm
Posts: 7
Post Re: GBTimelapse questions
Thanks for the replies. I've taken care of the aperture flicker by using the lens twist method. I was still having flickering issues so I got in touch with Mike from Granite Bay and got a wonderfully helpful reply in a couple of hours.

Turns out I made a rookie mistake and hadn't ticked the MX button next to the bulb timing. In my setup once the Tv dropped below 1/10s it handed over to the camera which caused the exposure to drop in 1/3 stop intervals. That gave the luminance curve a sharp sawtooth. All sorted now and I've used GBDeflicker to clean up the result from my pre-dawn shoot the other day.

One final beginner follow up question... In the holy grail shots I'm planning I'm faced with either using an ND OR handing back over to Manual exposure once the sun gets brighter to keep the exposure on target. From my tests our ND filters cause vignetting and a saturation and colour shift that I haven't been able to effectively correct in post. The only effective answer is to do a half second cross fade between the pre- and post-ND halves of the shot. Not the end of the world but not ideal if there is any continuity in the shot (boat travelling past, clouds moving, etc). Alternatively I let the camera do it's 1/3 stop thing again and hope I can deflicker in post. To date I've corrected some, but not all, of the flickery shots I've done, so that has inherent risk as well. Unfortunately I don't have access to a manual declicked lens or aperture ramper. What do people usually do when in this situation?


Sun Feb 08, 2015 8:21 pm
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Joined: Thu Feb 18, 2010 4:47 am
Posts: 388
Location: St Gallen, Switzerland
Post Re: GBTimelapse questions
I never used ND filters with GBt so can`t help you there.

Not having a declicked lens needn`t cause you to lose the aperture ramp possibility. Have you seen this?:
http://www.vimeo.com/82979584

Here Mike puts his ND boxes to use by doing 3 manual aperture changes instead of 3 ND filter changes. I haven`t tried it myself and it needs the exact ie real apertures to be determined at home the way he describes, but it`s a clever idea.

Note that a manual lens with manual aperture is required.


Mon Feb 09, 2015 1:07 pm
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