September 1, 2010

The Rolling Shutter

Filed under: Main — admin @ 12:01 am


The technical and confusing way that digital cameras snap pictures is leading a whole new type of photography.

You may have seen the results of a rolling shutter digital image. In addition to the thumbnail shown above, there are also popular pictures of airplane propellers, such as this one:

No, that isn’t a new airfoil. It’s what happens when the shutter on a digital camera moves too slowly to properly capture a moving image. The result is a stroboscopic effect on anything moving the image, a non-reality.

The reason for the effect is that the shutter on a digital camera, such as the typical cell phone camera, rolls across the CCD. So the left or top portion of the image is captured first, and then the middle part, and finally the rest of the image. That time span is fast enough to capture most images, but slow enough to make mincemeat out of moving images.

Occasionally, however, the rolling shutter produces some curious effects on rather static images:

In the above image (click for a larger version), you see what appears to be the reflection of the little boy’s internal demon on the right; the demon has his eyes open and the little boy (not the reflection) has his eyes closed. Again, the reason is a rolling shutter.

In the case of the little boy, the timing was just perfect enough to catch the boy blinking on the left, but with his eyes starting to open on the right. (Or it could be the other way around.)

As cell phones become more common as cameras, you’ll doubtless see more images like the ones shown in this post. In fact, you can search Google Images for rolling shutter and between the images of windows blinds you’ll find some excellent examples.

Or maybe some rolling shutter images already exist inside your digital camera or phone? Who knows?

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