Time-Lapse Photography
by Dennis Allen

July 30, 2011

August 28, 2011

If you want to duplicate my first attempts at time-lapse, you need to set your camera on a tripod with a 12-50mm lens. Camera on manual, ISO1600 or better, shutter speed bulb (infinite). Camera lens set to manual and focused to infinity. Start off with large JPEG images. Somewhere in your cameraís menus is a dark frame subtraction mode. In other words, after a 30 second JPEG exposure the camera will take a 30 second dark frame. This dark frame is CCD noise and  is automatically subtracted from the JPEG image. On my Canon Rebel XSi 450D it is called "Long Exposure Noise Reduction", found in the custom function settings. Turn it on.

Youíll need an intervalometer. That's an external trigger mechanism thatíll take continuous 30 second shots. On amazon.com I found "Timer Remote Control RS-60E3 For Canon XS XSi T1i XT XTi" for $16.95. Does the same job as an expensive $150 unit. The intervalometer should have three modes: Duration. For my unit, it's set to 30 seconds. Delay. For my unit, it's set to 62 seconds. That's 30 seconds for an image, 30 seconds for the dark frame, and a couple seconds for any shutter bounce (note that some intervalometers don't need duration time added to delay time). Number of Images. Set it to infinite. The number of images will depend on how long you run the camera. With the display screen off, I can get about four hours on one regular battery.

To avoid dew, I'll hit the camera once an hour with a hair dryer between shots. If I know it's a dewy night, I'll wrap the lens with an Orion dew zapper set on low.

After a night worth of images, upload the camera JPEG images to a new folder on your computer. Check your images. If they're too dark, might have to adjust the images to bring out detail. I like to use PhotoShop Elements. "auto level" does a nice job bringing out the Milky-Way in many of my runs. The latest PhotoShop Elements has a batch mode, so once I figure out how to adjust one image the batch mode can duplicate that adjustment for all images. Oh, make sure to save your JPEG images at their highest resolution.

Next, youíll need QuickTime Pro. Download a copy of QuickTime from the Apple web site and purchase the registration for $29.99. From the registered QuickTime Pro, select File->Open Image Sequence, browse to the new folder, select the first image in it, and specify the numbers of frames per second. I like 12 frames per second, but 24 frames a second is pretty standard. Once the images are loaded, youíll have a new window. From there, you can select File->Export. Under Export, Movie to MP4, select the Options button. Set the file format MP4, not MP4 (ISMA). Set the video format to MPEG-4 Improved. Set the data rate to 1024 Kbytes/sec.  Set the image size to custom, 1280x720HD, preserve aspect ratio using fit within size. Set the frame rate to current, the key frames to 12 frames.

Is anyone familiar with these options? My videos are still coming out a little grainy. My 450D camera produces 4272x2848 images, but if I try to save the video at that size I'll get a 12Mb file. I need to figure out is how to reduce the file size, yet avoid the grainy images.

Anyway, that should get you started. Once you're comfortable with the process, you might want to try different techniques to get better results. You could, for example, try to take continuous 30 second shots without dark subtraction. There would be no need for a 30 second pause between shots, thus doubling the number of shots. At the end of the session, take a 30 second shot with the lens cap on for a dark frame image. Then you can manually subtract this dark frame from all the other images.

Note: You might want to create a library of dark frame shots for your camera. That is, a set of dark frame images taken with different time lengths and at different temperatures. For example, is you ran a set 30 second images last night and it got down to freezing, you'll need a 30 second/32 degree dark frame.

The next thing to try is shorter exposures with a higher ISO. A 15 second exposure at ISO6400, for example, might be the equivalent to a 30 second ISO1600 shot. A 15 second shot is so short, you wouldn't be a need to subtract a dark frame from it. Which means more than doubling the number of exposures in a given session.

You could try taking RAW images. I understand the software that comes with the new Canon cameras is pretty good. And you'll need to play with RAW images if you want to learn to stack images later on.

You might also want to play with Photoshop Elements. Instead of "auto level", manually adjust levels. I tried to slid the levels scale over from 0, 1.00, 255 to 0. 1.0, 100. Seems to get better images, but I haven't figured out how to do it in batch mode.

I understand Apple discontinued QuickTime for Windows. I also understand Microsoft discontinued Windows Movie Maker (you can still find download copies, just no support). Haven't seen what time-lapse people now use, but I suspect either GoPro Studio or a version of Photoshop like PhotoshopCafe. If you are successful using different software, let me know which software you used and what settings were needed.

If anyone else has any suggestions for settings, software, etc., again, let me know. You can see my current collection by clicking here. For other attempts at time-lapse photography, see Randy Halverson's Milky-Way masterpiece or see the work done from the VLT in Chile. When I learn more techniques, I'll update this article.

July 30, 2011, Earth rotating

Here is my first attempt at keeping the star field fixed. Used Picture Window Pro, composite tool, operation registry. Anchored on the first image, shifting subsequent images. A lot of hard work. If I ever try it again, I'll triple the original the original work area. I wonder how the clip would look if we started the anchor on the last image instead of the first?

 

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