1 Topic by 1-21Giggawatts

  • 1-21Giggawatts
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Hi guys, i bought an OV4689 based high speed camera for Kayeton. Im running the latest version of Kinovea and I can configure the camera to record in 3 different modes:

1920X1080 MJPEG 50fps
1280X720 MJPEG 100fps
640X360 MJPEG 330fps

I am using this for golf swing analysis - however im finding that at 100 FPS in getting a lot of club motion blur - I really need to be able to record at 330. The issue with 330 is that there is a flicker in the image that makes it unwatchable has anyone else managed to get this working? I also cant seem to get any of the manual autoexposure settings working - is this still an issue for this camera? not that impressed with it to be honest - feel like i may have wasted my money :-(

2 Reply by preludesam

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however im finding that at 100 FPS in getting a lot of club motion blur

Motion blur comes from the shutter speed/exposure time of the camera. Frames per second are the number of captures over a period of time and will not impact the blur you are seeing unless it is also adjusting the shutter speed/exposure time. You can have 30 fps captures that are perfectly still shots with no blur if you can decrease the exposure time. 

The issue with 330 is that there is a flicker in the image that makes it unwatchable has anyone else managed to get this working?

This may be due to LED lighting or a projector where the frequency of the on/off cycling is being picked up by the camera.  Remove the projector or lighting you currently have from the equation. Please remember the projector is probably refreshing the lighting source at 60Hz. This means the bulb is flashing at 60 times per second and the camera will capture the on/off cycling. Most dimmable LED bulbs can address the issue with this and there is a ton of information on using the correct lighting for high-speed recordings. Try to record one camera outside with sunlight and see if you are still experiencing issues.

These two issues may be one and the same and you may find the FPS is tied to the exposure time.  I found out the hard way that a really nice high-speed camera looks poor without the correct lighting. To give you an idea have around 15k lumens for my swing recording setup. I would advise anyone going this route if you want perfect stills of the golf swing you really need closer to 60k lumens or more and crank the exposure time as low as the lighting allows. You will need access to exposure time settings to get the most out of the camera. The manufacturer should have an SDK for you to adjust settings.

3 Reply by petecrowe

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An excellent and informative answer preludesam!

4 Reply by obevz (edited by obevz 2021-12-02 05:08:05)

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I had an issue with flicker of my high speed cameras...(I have USB2 150, 330 cameras as well as 525fps Basler USB3 camera).
I found it was the "non" DC LED lights I purchased. You can purchase LED lights that do not flicker as they convert from AC to DC...also - reflection from a Projector can also cause some image flicker. High wattage non flicker DC LED lights are available to 200W - Aliexpress  (China) sells these for around $US15...in the older non-cooling light format. I found these died after about 40 hours of usage - basically from overheating. These lights have a smooth plastic dome (~10cm high) over the LEDs. That dome captures the heat, and the electronics fail. So I just remove the dome and have "naked" leds...they last longer. Take care when removing the dome.  There are now newer 150-200W LED dc lights from Aliexpress and these are identified by the heat sink wings around the base/electronics and very flat plastic covering. (maybe 2cm) They cost a bit more...and I have not tried them yet. Caution with these high wattage LED lights - the screw-in base neck is rather delicate and over-tightening has caused a few lights to snap the internal connections...shade. Happy to provide more info if needed.

Other things that can result in club motion blur is the type of camera recording process... check out Rolling Shutter vs Global Shutter. Many good bits on info here are Kinovea.

Regs Oscar in Australia