I received an interesting email last week from Jo-ann, a quite concerned subscriber...
"My family and my parents were camping at the Lower Sabie Camp in the Kruger National Park. There, at about 8pm, my mother took the attached photo, using automatic focus and the 'night time' setting on her camera.
"When we looked at the picture on the camera's LCD screen, we noticed the
funny 'squiggly' light and figured it was a moth or something.
"Today, my 15 year old daughter was looking through our holiday photos and
noticed a woman standing behind my husband. When I looked at the picture, I couldn't believe my eyes as there definitely was nobody behind us when the photo was taken.
"Could you perhaps explain to us what the 'vision' could possibly be?"
Sure Jo-Ann. Rest assured, it's not a ghost or spectre!
Looking at the EXIF information for the picture, I can see that the shutter was open for 2 seconds. Because there wasn't much light (and no flash was used), the camera set a long shutter speed to ensure enough light entered the camera to expose the shot correctly.
What happened was someone moved from left to right in the back of the photo while the shutter was open. You probably thought no one was there because most of the time people were not walking behind the subject.
While the shutter was open, the person moved from directly behind the subject towards the right. As the shutter was open for the whole time, you see not only the person, but what was behind them as well.
The squiggly line is caused by the moving person holding a torch (probably so they could see where they were going). It's squiggly because the walking motion moves the torch up and down as well as to the right. If you look closely, you can also see the brighter patch of dirt where the torch shone.
The long shutter time has also contributed to the shot being blurry. There's two ways to fix this for next time:
- Increase the ISO. This shot was taken using ISO 400, but the camera (a Canon 350D) is capable of taking shots at ISO 1600. The higher the ISO number, the more sensitive the camera is to light, and the less time the shutter needs to be open.
- Use a tripod! If you are not using a flash for a night shot, you really need a tripod. If the shutter speed is more than about 1/50 second, you'll get a blurry image even if you try to keep your camera still. The newer cameras have image stabilization technology that cut the 'hand held' speed to 1/30). You can also see my tip on avoiding shake.
Although the effect was unwanted here, slow shutter speeds can be used for some cool special effect photos, like this Rhino shot. Place your camera on a tripod, set the shutter on a long (15 second exposure) and 'paint' around the object using a torch or colored light (or in this case a LED light).
Thanks to Jo-Ann Meiring, her mother, Lucy Wagner, and Søren Ludvig for the use of their images.
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