Saturday, September 21, 2013

Bramping (Bulb Ramping) on the Cheap.

Bulb Ramping, or "Bramping", as it is commonly called, is a technique of creating time-lapse videos by using the 'bulb' mode of the camera, and controlling each exposure using an external timer. These type of time-lapse videos tend to give very smooth transition between day and night (and vice-versa), instead of the flicker you tend to get if you leave the exposure for the camera to determine (or if you change the exposure manually).

Compare the video above (created using the 'Bramping' technique), to the one below, in which the exposure was manually increased to compensate for the rapidly changing light. The changes in exposure give the video (the one below) a very jarring effect. In fact, this was my first attempt at time-lapse during a sunset.


As long as you are doing time-lapses where the light is fairly stable (during daytime and nighttime), you can rely on the standard intervalometer (either built in your camera menu, or an external device that connects to your camera to trigger exposures at set intervals). For example, on my D800, I can use the menu function to activate interval shooting for normal daytime or nighttime time-lapses.

Intervalometer menu on a D800 for standard time-lapses.
The problem comes when you are doing time-lapses during sunset or sunrise. For example, during sunset, the light is rapidly changing from bright to dark. You need to compensate for this fading light by either:
  a. Reducing the shutter speed (example: If you current shutter speed is 1/200th of a second, then you need to reduce it to 1/160th of a second, or lower). And you need to keep reducing as it becomes darker.
  b. Increasing the ISO (for example if the current ISO is 100 you could increase the ISO to 125, or something higher). You would keep increasing till you reach the maximum ISO setting available in your camera. Most modern cameras go up to 6,400 and some professional models go a bit higher than this.
NOTE: for smooth time-lapses, you should leave the aperture (f-stop) constant otherwise, it will affect the depth-of-field resulting in an inconsistent time-lapse.

In fact, if you left your camera on "Auto" mode or some of the Semi-Auto modes like "P" (Program Auto) or "A" (Aperture Priority), that is exactly what the camera would do to compensate for the changing light. The side-effect of this changes in exposure between each shot, results in flicker. There are software solutions to overcome the flicker problem. GBDeflicker is a popular tool used to remove flicker caused by changing exposures during a time-lapse. It requires extra time in post-processing, and the results may not always be the best.

That brings us to Bramping. Bramping is the most accurate and high-tech method for creating smooth time-lapses between day and night (and vice-versa). To better understand when we need to switch to Bramping, I have created this handy illustration.

The yellow lines indicate times when you need to switch to Bramping.

Up until now, you required expensive gadgets to program and execute Bramping. The Promote control is possibly the most popular, and also the most versatile. However, it runs into several hundred dollars, and should appeal to only the most dedicated time-lapse photographers.

I happened to stumble into Bramping, when I ordered the Triggertrap dongle from Amazon.

Triggertrap Dongle for Nikon (DC0, 9 pin connector)
The amazing thing about this affordable product is that Bramping is not its primary function. It main function is to trigger your camera using sound (more about that in another post). However, since the device is controlled via a smartphone (both Android and iOS is supported), the clever developers at Triggertrap bundled a whole host of bonus features in this tiny device. Bramping just happens to be one of these bonus features. You are essentially getting the Bramping feature for free. And free (in my opinion) is always good.

To get started, you connect the 3.5mm jack to your smartphone headphone socket, and the camera connector to your camera. Triggertrap supports most major camera brands. Depending on your camera connection, you choose the appropriate connection cable. The software/app to control the device is available for free in the Appstore (for iOS devices), and Google Play store for Android devices. In my case, I used my old Samsung Galaxy S2. This is how the setup looks like.

Triggertrap dongle connection.
To start the Bramping sequence, you input the following values into the app:
   a. Shutter speed of the first exposure.
   b. Shutter speed of the last exposure.
   c. Number of shots that the app should trigger on your camera.
   d. Time the sequence should take, starting of the first shot to the last shot.

Before we understand how to set these 4 parameters correctly, we need to prepare a check-list for the camera itself. I have learned through experience that it is better to have a written checklist with you, because ignoring any one item could render your whole time-lapse useless, and a waste of your time.

For proper time-lapse, a sturdy tripod is mandatory. Place the camera on the tripod, and make the necessary connections to the Triggertrap dongle, and the smartphone. One problem with the supplied cable is that it is very short, so you will need a way to secure the smartphone close to the camera. I happen to have one of those sports armband that you use for running, which works perfectly to keep the phone secure, and keeps everything neat and tidy.

Keeping the smartphone secure with a sports armband.
Once the camera is set, choose an appropriate composition and make the adjustments to the camera to make it ready for Bramping. The following check-list can be helpful to ensure that all the settings on the camera are enabled.

Checklist for your camera.
Once everything is set, it is just a matter of opening the app, setting the 4 parameters, and hit on the 'START' button to start the time-lapse process. How you set these 4 parameters will depend on the time of time-lapse that you want.

1. Shutter speed of the first exposure: This is normally the easiest one to figure out. Based on the current light, you can test the first exposure to ensure that it is correctly exposed. Currently, the app does not allow you to shoot faster than 1/15th of a second. So you will have to make the necessary adjustments to ISO and/or aperture settings to ensure a properly exposed image. You can take a test image and check to ensure it is neither over or under-exposed.

2. Shutter speed of the last exposure: This is normally the most difficult value to input. The proper way to know this value would be to visit the place one day before, and monitor the light levels at different times of the day and night. For example, if the Bramping sequence starts at 6 p.m., and you want to show the transition up to 7 p.m., then you need to know what is the correct exposure at 7 p.m. This is the value you will input here. You can also estimate the value based on your knowledge. For example, in my time-lapse, I estimated the ending time to be a 15-second exposure. In my case, it turned out to be pretty accurate.

3. Number of shots that the app should trigger on your camera: This is really your preference. More pictures means better control over the final output.

4. Time the sequence should take, starting of the first shot to the last shot: This is self-explanatory.
Depending on how you adjust one parameter, the other parameter may automatically change.

What about noise reduction?
Depending on how you have configured sequence, enabling noise reduction may cause some of the shots to be missed. I normally set my NR to OFF to avoid this problem.

That's about it. This is really a neat gadget to explore the world of changing light.

A few things I would like the developers to add to the current app, to make it more flexible:
1. Ability to shoot faster than 1/15th of a second. Somehow I suspect this limitation is due to most camera's inability to register a start and stop sequence in bulb mode faster than 1/15th of a second.
2. The sliders for changing values on the Android app are woefully small, and difficult to set precise values.
3. Ability to set the start time for bramping. This would allow one to combine normal time lapse with a bramping sequence.

1 comment:

Bosque Bill said...

Thanks for the informative post. I've just gotten my TriggerTrap and want to record sunsets with Bramping. Found your post while searching for help setting the shutter speed of the last exposure

The range in version 2 of the app seems to be 1/16 sec to 8 seconds, at least on iOS, not the 15 sec you mention in your post.

I'm new to this. Do you have any additional advice or have you found other resources to help estimate the last exposure? I'll practice at home, but while traveling I'll only get one shot at a sunset (or sunrise) at my destination.