Friday, April 11, 2008

Rolling Shutter Effect In Sony EX-1

In the April, 2008 issue of DV Magazine I reviewed Sony's EX-1 camera.

I love the camera, warts and all, and it is high on my post-NAB purchase list. This is coming, you understand, from an unabashed user of the Panasonic HVX200 and long-GOP skeptic.

But one of the concerns that many users have raised about the EX-1 is its CMOS "rolling shutter" which effectively scans the entire image progressively rather than buffers the image as does a CCD-based device.

This rolling shutter effect can produced partially-exposed frames under certain conditions, primary among them being strobing or flash photography.

I was able to reproduce this in my testing subsequent to the article. I'm shooting at night at the Rockefeller Center ice rink using existing light (those half-inch chips really do well in low light situations). Of course, every parent needs to snap their kid doing multiple axils.

Take a look first at a single frame before the flash.

Now, the next two frames contain the flash.

Can you see the rolling shutter effect? Look at "The Concourse..." You can see that the area is normally exposed in frame 1 and brighter in frame 2. So, the flash effectively "rolled" from the bottom of the frame to the top.

But does it really make any difference in this scenario?

Take a look at a 4 second clip shot 720p24 at 60 fps for a slow-mo effect. The flash occurs about 3 seconds into the clip.

The flash is certainly visible but even when played at full HD resolution the shot still holds together.

I'll keep trying to break the rolling shutter. Stay tuned...