It's a function of how the sensor is programmed.
Frame interval and hence max exposure is documented at https://www.kernel.org/doc/html/latest/ ... ra-sensors
Reading from the sensor driver (https://github.com/raspberrypi/linux/bl ... c/imx296.c) as I haven't got a sensor attached at the moment.
The pixel rate for imx296 is 1188000000 pixels/sec.
The max value for VBLANK + height is 1048575 lines (20 bit register).
HBLANK + width is a little more complex on this sensor, but appears to translate to 1760 pixels.
1188000000 / (1048575 * 1760) = 0.643730777fps, or 1.553444446 seconds/frame.
That looks like either I've made a factor of 10 error, or whoever wrote the docs has. If you have a sensor connected, then "rpicam-apps --list-cameras" will confirm the min and max frame rate for each mode.
In theory HBLANK + width could be made variable to increase the time per line, but that would require some reading of the datasheet to confirm that Sony really do support varying that parameter on this sensor.
IMX477 and IMX708 both have a register to multiply up the frame time and exposure time by powers of 2 up to x128. I don't believe IMX296 has that option. That's how they get up to 670 and 112 seconds respectively. IMX477 also has a fully configurable HBLANK value, hence getting up to 670 second frame times.
Frame interval and hence max exposure is documented at https://www.kernel.org/doc/html/latest/ ... ra-sensors
Reading from the sensor driver (https://github.com/raspberrypi/linux/bl ... c/imx296.c) as I haven't got a sensor attached at the moment.
The pixel rate for imx296 is 1188000000 pixels/sec.
The max value for VBLANK + height is 1048575 lines (20 bit register).
HBLANK + width is a little more complex on this sensor, but appears to translate to 1760 pixels.
1188000000 / (1048575 * 1760) = 0.643730777fps, or 1.553444446 seconds/frame.
That looks like either I've made a factor of 10 error, or whoever wrote the docs has. If you have a sensor connected, then "rpicam-apps --list-cameras" will confirm the min and max frame rate for each mode.
In theory HBLANK + width could be made variable to increase the time per line, but that would require some reading of the datasheet to confirm that Sony really do support varying that parameter on this sensor.
IMX477 and IMX708 both have a register to multiply up the frame time and exposure time by powers of 2 up to x128. I don't believe IMX296 has that option. That's how they get up to 670 and 112 seconds respectively. IMX477 also has a fully configurable HBLANK value, hence getting up to 670 second frame times.
Statistics: Posted by 6by9 — Wed May 15, 2024 9:15 pm