Tag Archives: global

NEX-FS700 Significantly reduced shutter when in Super Slow Mo!

UPDATED WITH NEW FRAME GRABS FROM STROBE LIGHT AT BOTTOM.

One of the things that did concern me slightly about the FS700 was how would the sensor behave in Super slow Mo. The sensor is a CMOS sensor, so I expected it to exhibit rolling shutter artefacts, which it it does indeed do when in standard shooting modes and S&Q motion. It’s not bad, but you can make the pictures skew and when you try to shooting something like a spinning propellor you can get some weird effects, especially at higher shutter speeds. However when you switch the camera to Super Slow Mo the rolling shutter effects appear to go away. I was able to shoot propellors, do fast pans, shake the camera about etc and there was little sign of the usual rolling shutter artefacts.

FS700-Fan-Norm2-300x168 NEX-FS700 Significantly reduced shutter when in Super Slow Mo!
FS700 25P 1/100

Just take a look at these two frame grabs. One shot done at 25P with a 1/100th shutter, the other done at 100fps with a 1/100th shutter, so in both cases the shutter speed is the same, so you would expect the rolling shutter artefacts to be the same, but clearly they are not. In standard mode the fan exhibits a typically lop sided, asymmetrical look and the fan blades appear curved, the upper and lower fan blade both bent towards the right of the frame. But in Super Slow Mo mode the fan blades are straighter and the fan is a lot more symmetrical with noticeably less bias towards the right, notice in particular the differences in the lower fan blade.

FS700-Fan-SS2-300x168 NEX-FS700 Significantly reduced shutter when in Super Slow Mo!
FS700 Super Slow Mo 1/100th shutter

You can tell the shutter periods are the same as the amount of motion blur and spreading of the fan blades is near identical, so it’s not a shutter speed difference, this is clearly a sensor scan difference. This is very interesting and requires further investigation as it suggests that the sensor read out process is different in the high speed mode. It is probably just a significantly faster scan rate, but it could also possibly be a global shutter of some kind. It’s just a shame that you can’t access this read out mode for normal shooting.

UPDATE:

FS700-Norm-Flash-300x168 NEX-FS700 Significantly reduced shutter when in Super Slow Mo!
FS700 Flash band at 25fps 1/100th shutter.

Here are a couple more frame grabs done with the strobe focussing flash from a Canon DSLR. In both cases the shutter speed is 1/100th of a second so you would expect the width of the “Flash Band” to be the same. The narrower the band, the slower the sensors scan speed. These frame grabs suggest the scan speed is around twice as fast when in Super Slow Mo. It’s not a global shutter, but certainly a nice improvement. This is 100% repeatable.

FS700-SSM-Flash-300x168 NEX-FS700 Significantly reduced shutter when in Super Slow Mo!
FS700 Flash band in Super SlowMo 100fps, 1/100th shutter

You can take advantage of this for normal speed shooting by setting the camera to SSM and  recording the SDior HDMI feed to an external recorder.

Speculation: There is a little more aliasing when shooting in SSM. Is there some line slipping going on perhaps during SSM? This would allow a faster scan speed as fewer lines of pixels are read and thus might account for both the slight aliasing increase and the faster read out speed.

Advertisements