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Sony a7c: readout speed (video mode)

I measured the sensor readout time of the Sony a7c in photo mode when using Silent Shooting (full electronic shutter). Now it's time to explore the video modes.

The methodology is the same: a fast blinking (500Hz) LED is recorded. One pair of lines (dark line and light line) is 2 ms of the sensor reading.

1. Full-frame width, 4K 25/24 fps [PAL/NTSC]

About 12.4 pairs, 24.8ms.

2. x1.2 crop width, 4K 30 fps [NTSC]

About 8.6 pairs, 17.2ms.

3. Full-frame width, Full HD 25/50/100 fps [PAL]

About 4 pairs, 8ms.

4. Full-frame width, Full HD 24/30/60/120 fps [NTSC]

About 3.6 pairs, 7.2ms

5. APS-C, 4K 25 fps [PAL]

About 7.9 pairs, 15.8ms

6. APS-C, 4K 24/30 fps [NTSC]

About 6.9 pairs, 13.8ms.

7. APS-C, Full HD 25/50/100 fps [PAL]

About 3.9 pairs, 7.8ms.

8. APS-C, Full HD 24/30/60/120 fps [NTSC]

About 3.4 pairs, 6.8ms.

Reading in 4K modes is rather slow.

You can see that Full HD modes do not use the same sensor area as 4K, it skips lines. This causes a lot of aliasing, so I find Full HD on the Sony a7c useless.

The value of sensor readout speed is very important for software stabilization with Gyroflow (at least in 4K). It is necessary to always enable "Rolling shutter correction" and set "Frame readout time".

An inaccurate value or a deactivated correction will not allow to achieve a good stabilization.

See also related notes:
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