Wednesday, October 26, 2011

Case Study #1: The Easy Expert Method

In this post, I show you how to get the near-perfect results of Expert Method, with just one filter. This keeps your gear to a minimum, and your setup simpler to operate.

I’m really happy with how smoothly GBTimelapse’s AutoRamp function is working. All I needed to do was start up the time-lapse software, watch the progress from my folding chair in front of the sunset, and step in at one point to take the filter off. A side note: I recently made the font on the bulb exposure time larger, so I can sit about ten feet away from the laptop and still keep an eye on it.

You can make great time-lapse with inexpensive gear. Last night I captured a pretty cool time-lapse of a Lake Tahoe sunset followed by the Milky Way. Instead of an expensive Canon 5D Mk II, I used a Canon 60D, which has a smaller and lighter body. And instead of using the AutoRamp Expert method with three ND0.9 (three-stop) neutral density filters, I simplified things and only used one ND1.2 (four-stop) filter.

I call this the "Hybrid Method" - simpler than the Expert Method, but very effective.

You use filters when the sky is too bright for bulb exposure. Bulb exposure settings are not camera presets, they are infinitely variable up to 1/1000 of a second. So, the most precise.

I used a 4-stop neutral density filter to get the initial daylight bulb exposure time to 0.4 seconds. Longer bulb times are better, because they are more accurate and repeatable than bulb times near a camera's minimum.

As the sun set, AutoRamp ramped the Av from f/22 to f/4, the ISO from 100 to 3200, and the bulb time from 0.4 seconds to 30 seconds. As I relaxed by the lake and sipped on a beer, the software automatically ramped down the exposure, ramped up the time-lapse interval, and ramped the white balance color temperature. I did have to get up to pause briefly to remove the ND filter about 20 minutes after sunset.

Watch this video showing the camera and AutoRamp setup...

There was a tiny amount of flicker in the beginning at high f-numbers, but that dissipated once the Av got down to f/4 and the bulb time increased. That little bit of flicker was easily removed using GBDeflicker.

BTW, the Canon 60D battery had no problem with this 3.5 hour and 660 image time-lapse.

Tuesday, October 04, 2011

How GBTimelapse 3.1 uses your GPS coordinates to reduce flicker

GBTimelapse 3.1 comes with a powerful new feature called AutoRamp, which I’ve mentioned in some previous posts here and here. AutoRamp is engineered to reduce flicker in several different ways - it’s a unique tool unlike anything else on the market, as you’ll see here....

In this post, I’m going to show you how inputting your GPS coordinates into the software can dramatically reduce flicker at sunrise and sunset. There’s some powerful mathematics and a great deal of research backing up this tool, but it’s very simple for you to use.

Behind the scenes in GBTimelapse 3.1, AutoRamp uses a moving average of past luminance values to calculate the correct exposure settings for the next image. This method works fine unless the scene brightness is changing rapidly during a sunset or sunrise. When the sun is below the horizon during twilight, the exposure can change by up to two full f-stops every ten minutes. Bad news for a time-lapse!

Here’s how GBTimelapse 3.1 is a gamechanger: if you’re in a situation with rapidly changing brightness, simply input your GPS coordinates. With this info, the AutoRamp function will predict the correct exposure by calculating the sun’s changing elevation relative to the horizon.

Wow! In other words, to give you the best exposure at sunrise or sunset, enter your GPS coordinates. The software will then anticipate the movement of the sun, adjusting your exposure accordingly.

It’s easy to get your GPS coordinates. Under the Tools/Options menu, check the Location tab to see this Windows form and use Google Maps to find your coordinates...

Also, make sure your computer clock and time zone are also set correctly. The current sunrise and sunset times are shown - make sure they are correct.

To use the location information, check the box labeled “Use Sunrise/Sunset compensation” under the AutoRamp tab. Have fun with your time-lapse!