Wednesday, August 29, 2012

GBTimelapse - New Feature - Automatic ISO shift for ND filters

New Feature in GBTimelapse Version 3.6.1!

When using a large ND filter, AutoRamp will now automatically adjust the ISO shift time when the filter is added (or removed).

All you have to do is add (or remove) the filter, and AutoRamp will take care of the rest.

GBTimelapse - "Holy Grail" Sunrise Demo

Most of the time I use GBTimelapse AutoRamp to capture a landscape time-lapse at sunset. But occasionally I get up early enough in the morning to do a sunrise.

A couple of weeks ago I was awakened at 3 AM by the sound of thunder. Lightning storms are rare in this part of California, but it sounded like a good storm was headed my way. The previous evening I'd been running some tests with my Canon 7D, so it was already set up in an upstairs window. I quickly fired up my computer with the hopes of capturing some lightning in a sunrise time-lapse.

Here's a demo showing how to set up a sunrise AutoRamp time-lapse, and the resulting video. I did manage to get a couple of good lightning bolts.

The strike you see in this frame knocked out power for a couple of minutes. GBTimelapse was running on a laptop so it was unaffected. However, the camera was running on AC power, so I did miss a couple of frames.

Friday, August 24, 2012

GBTimelapse - Holy Grail Sunset - 5D Mk III with 9-Stop ND

In a previous post, I showed you How To Calibrate a 9-Stop ND Filter.

Here's a tutorial showing you how to setup GBTimelapse AutoRamp to do a Sunset time-lapse using a single 9-stop neutral density filter.

... and here's the resulting video, captured using a 5D Mark III with 16-35 mm lens. The Milky Way was brilliant that night.

Pros & Cons of the 5D Mark III

A major advantage of the 5D Mark III is the ISO 50 setting. It allows you to use a one second bulb time at f/2.8 with a 9-stop filter during daylight.

However there are two minor disadvantages to the Mark III. First, the Depth-of-field Preview button has been moved to the other side of the lens from the Lens Release button making it awkward to do the lens-twist procedure. Second, unlike the Mark II it's not possible for GBTimelapse to change the AEMode - you must do it manually on the camera Mode Dial.

Tuesday, August 21, 2012

GBTimelapse - How To Calibrate a 9-Stop ND Filter

Simplify ND filters by using only one

Lately I've been using a single 9-stop filter to capture time-lapse during sunsets. By using a single 9-stop, I only need to make one filter change while the sun is setting. Previously, I used a stack of three 3-stop filters. But the filter stack added to vignetting, and using just one is much simpler.

The easy way to calibrate your ND filter

When using GBTimelapse AutoRamp in bulb mode with neutral density filters, it's best to know the exact value of each filter. Even though a filter may be rated at 9 stops, it may not be exactly 9 stops.
I have found filters that are more than ten percent different from their rating.

To avoid a change in image brightness when adding or removing a filter, AutoRamp needs to know the exact number of stops of the filter. There's an easy way to calibrate a filter using AutoRamp itself. This video shows you how:

GBTimelapse - Mike Lanfor's 3-Axis MoCo Tutorial

Mike Lanfor put together a great 3-axis motion control tutorial on using GBTimelapse AutoRamp with a Dynamic Perception Stage Zero Dolly and Merlin Pan/Tilt head. Check it out below:

He also shows off some cool gear from Goal Zero for providing power in the field.
  • The Sherpa 50, a 50-watt battery pack to extend the run-time of his laptop computer and provide USB power
  • The Nomad 10 solar panel for charging the battery
This kit should be all you need for an extended time-lapse trek into the wilderness away from power sources.

Thanks to Mike for the great work!

GBTimelapse - AutoRamp with 3 ND Filters

Walk-through using GBTimelapse AutoRamp with 3 ND filters

Last fall during a visit to San Francisco, I stayed at a hotel in Emeryville across the bay. I always ask for a room with a view and was lucky to get one on the eleventh floor facing the SF bay. This was a great vantage point for a time-lapse. I used my 5DMkII with 16-35mm lens on a Manfrotto tripod and ball head, with the camera tethered to my Lenovo laptop. Since I was in a hotel room I had AC power for both the camera and computer. I was able to get both the sunset and the sunrise. The window wasn't very clean, but with the camera focused on infinity it looked right through the window grime. Below is the result, with some of the night footage removed to make it shorter.

Technical setup
After achieving a good focus, I set the lens to manual focus and attached three ND8 filters. At 3 f-stops each that gave me a total of eight stops light reduction. But the sky was so bright, 8 f-stops was not enough to set the aperture at f/2.8; so I had to start the time-lapse at f/5.6 and rely on AutoRamp to reduce the Av down to f/2.8 as the sky darkened.

Watch the video below to see how I setup the AutoRamp parameters. It shows the process of removing ND filters at sunset and adding ND filters at sunrise.

There is some bright flashing in the video as the sun peeks out from the clouds. A couple of times that bright sun caught the dirt on the window and gave a bright flare over the screen.

The night sky wasn't very dark because of all the bright lights. The yellow color of the city lights bothered me too. Since making this video I've added the ability to ramp the white balance color temperature with the sunset and sunrise. It's very easy to setup and I'll show this new feature in a blog post some time soon.

Facing into a bright sun like this is very difficult. With three ND.8 filters I started at f/5.6 and bulb Tv of 0.275". It would have been better to start at f/11 and a bulb Tv closer to 1 second. Longer bulb times are more accurate. When you use a short bulb time (near a camera's minimum) the bulb timing error produces some flicker. I could also have done better by using stronger ND filters. If I had used there ND1.2 filters for a total of 12 f-stops, I could have used longer bulb times.