Wednesday, October 31, 2012

New Feature: Use GBTimelapse with the MX2 for Precision Bulb Ramping

Question: Why is shooting in bulb mode is the best way to get flicker free time-lapse?
Answer: Because bulb exposure times can be set with a precision of 0.001 seconds. The precise, tiny increments allow smooth ramping of exposure when light is changing, i.e. at sunset or sunrise.

When you run GBTimelapse through a laptop connected to a camera, GBTimelapse uses a software timer to control the camera's bulb exposure times. Although the software timer can be set as short as 0.100 seconds, it is most accurate and repeatable at times of 0.500 seconds and longer. The accuracy at a shorter duration is limited because of Microsoft Windows, which is not a "real time" operating system.

New Feature

Now, GBTimelapse (Version 3.7) can use the MX2 Dolly Engine from Dynamic Perception to control bulb exposure times. Because the MX2 runs in "real time" it has a much more accurate timer not limited by Microsoft Windows. This allow you to use much shorter bulb times and still avoid flicker.

How-to and setup tips

On a 5D Mk II, being able to reduce shorten the bulb time from 1.000 down to 0.033 seconds adds 5 stops to the Tv range. This means you can do a daylight/milky-way time-lapse using only one 4-stop neutral density filter rather than one 9-stop (or three 3-stop) ND filters. And, you can do a daylight/city-night time-lapse with no filters at all.

To use the MX2, connect both the camera and MX2 to your laptop with USB cables. Then connect the MX2 "camera" port to the camera with a shutter cable and the "ext 1" port to the camera flash port with a PC/flash sync cable.


For bulb control you can run the MX2 with power from the USB cable. To do bulb control and motion control, you will need to power the MX2 with a separate battery.

For a demo showing how to set this up, please watch this video...



... and another demo showing how to use the MX2 for a sunset time-lapse...


Reference: 

Minimum accurate bulb durations for some camera models


ModelMX2 Bulb TimerSoftware Bulb Timer
5D Mk III0.040 seconds0.300 seconds
5D Mk II0.033 seconds0.300 seconds
5D0.067 secondsNA
7D0.033 seconds0.500 seconds
40D0.035 seconds0.400 seconds
T3i0.035 seconds0.500 seconds
XSi0.047 seconds0.400 seconds
XTi0.036 secondsNA


4 comments:

Aaron D. Priest said...

Very cool!

Ian Swarbrick said...

Mike, the Canon 600D is in your list but it only has a usb out and the flash hot shoe. No space for the three cables you show in the video. Is it somehow useable with this new technique? Thanks

tlapse said...

For the 600D, use a hot-shoe adapter to connect the PC/Flash cable. See my blog post http://tlapse.blogspot.com/2012/07/gbtimelapse-two-axis-dolly-control.html

Anonymous said...

Mike,

what's the minimum bulb time for the Canon 60D? Thanks
Albert.