Category Archives: Techniques

Easy Time-Lapse Videos

It’s simple to create a passable time-lapse sequence using an inexpensive digicam and some freeware.

You need an interval timer. I don’t know how many cameras have this feature. However, if you have a Canon PowerShot camera you can download a quite sophisticated bit of freeware called CHDK that, among other capabilities, functions as a user configurable interval timer. CHDK is well documented but the online wiki is a bit intimidating. Don’t worry. Go to this page and work your way down. It gives the essentials.

I used my Canon S95 with CHDK, configured to take photos continuously at five-second intervals. Put the camera on a tripod or other support, use JPEG rather than RAW if this is an option and deactivate your camera’s stabilizer if it has one. Focus manually if you can. Then point the camera at something interesting and start the interval timer. The video below represents about an hour and a quarter in real time, 924 exposures. (Your camera battery will run down pretty quickly doing this, so you may want to turn off the camera’s LCD if possible. The CHDK documentation mentions a way to trick the camera into turning off its LCD by plugging something into the “video out” socket, but I haven’t tried this yet.)

There are probably many ways to stitch the photos into a video sequence. I used Microsoft Windows Live Movie Maker, which is part of Windows Live Essentials, which may have come with your computer if you use Windows 7. (It’s also available as a free download here.) Simple to use: Start a new project, import your photos (batch edit them first if you want), select all of the imported photos, click the Edit tab, set Duration to .03 seconds (the minimum), hit the enter key to apply this duration to all of your photos, then save your movie using the quality setting of your choice.
 


 

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Image Sharpness: Shutter Speed, Handholding and Stabilization

This is an informative read. The takeaway is that making sharp hand-held photos requires faster shutter speeds than you might expect. The author suggests halving the exposure that’s suggested by the old reciprocal-of-focal-length rule of thumb: for example, use 1/100th of a second rather than 1/50th with a 50mm lens. I think this is optimistic, or to frame it differently, you will get an increasing percentage of sharp hand-held images as you continue to decrease your shutter speed to well below 50% of the reciprocal of your focal length. With a 50mm lens, for example, 1/100th second is better than 1/50th, but you are even more likely to get a sharp image at 1/250th, 1/500th or even faster. YMMV as they say on the Internet, and there is no substitute for experimentation to find what works best for you. In my case I often don’t get images that are routinely sharp at 100% magnification unless I use shutter speeds approaching 1/1000th of a second or faster. This means that I tend to get better results in bright sunlight at ISO 400 than 100, a result that surprised me when I first noticed it.

Related points to keep in mind:

-In fading light, any camera/lens combination will have an exposure length beyond which you will start to get too many blurry photos. With a modern DSLR it’s usually best to err in favor of increasing ISO sooner than you need to.

-There is no substitute for a tripod.

-Turn off image stabilization when you use a tripod, unless you determine by testing that stabilization helps. (Here’s a helpful discussion of issues related to stabilization.)

-It doesn’t take much wind or vibration (e.g., if you are standing on a heavily trafficked bridge) to degrade the sharpness of photos made on a tripod, particularly if you are using a lens of longer than normal focal length. Such image degradation is most easily detected by comparing 100% views of sequential photos made as part of a series to be stitched together, as for a skyline panoramic. Even subtle blurriness stands out.

-Some tripods are better damped than others. Use your camera’s live view feature, set on maximum magnification with a longish lens, to get a feel for how quickly your tripod settles down after you touch it or change camera positions. You may find that a conventional 1- or 2-second mirror lockup delay is inadequate and that you get sharper results by using a remote shutter release or even the full-length delay of your camera’s self-timer. This is also a good way to determine if it’s too windy to make sharp images with any technique.

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