There are many situations when exact frame time is required - Venus or Mercury transits, Moon or planets occulatations, satelite transitions, etc.

K3CCDTools2 enables to log capture frame times even in fast stream capturing mode (5, 10 or 15fps).
This log option must be set in Settings dialog - Video Capture tab - log to file check box:

Currently this logging in stream capturing mode is available only in Video For Windows capturing mode.

K3CCDTools 2.1 has also Camera Latency Calibration Tool, which shows exact PC time in a window.
It can be recalled by using menu (Tools - Camera Latency Calibration):

Measuring time latency between realtime image captured by webcam and time of arriving frame to computer

Testing setup:

1, I opened one instance of K3CCDTools 2.1 with Camera Latency Calibration Tool.
2, I aimed webcam to monitor (85Hz frame frequency) with calibration window
3, I opened the new instance of K3CCDTools 2.1 and started to capture video sequence in VFW mode with logging on
4, Result AVI was loaded into Sequence Processing part and Text Output Image filter was used for adding yellow time caption to frames.
It enabled me to see the difference between real time of capturing frame by camera and time of arriving frame to computer.

Yellow caption shows time, when frame arrived to computer. Imaged time is the real time captured by camera.

Here are settings of Text Output Filter:

And now results. Horizontal axis shows frame numbers. The vertical axis is time in milliseconds.

RealDiff - shows deviation of real time period between frames from 100ms interval. As you can see, this deviation is less than +/-10ms.
CapDiff - shows deviation of captured time period between frames from 100ms interval. As you can see, this deviation is in interval +10/-20ms.
Cap-Real Diff - shows time delay between time, when frame was captured by camera, and time, when frame arrived to computer. This delay is approximately 130ms (yellow trend line), +/-10ms.

RealDiff - shows deviation of real time period between frames from 200ms interval. As you can see, this deviation is less than +/-10ms.
CapDiff - shows deviation of captured time period between frames from 200ms interval. As you can see, this deviation is in interval +22/-13ms.
Cap-Real Diff - shows time delay between time, when frame was captured by camera, and time, when frame arrived to computer. This delay is approximately 235ms (yellow trend line), +/-15ms.

Conclusion

My measurements show, that time delay for ToUcam camera is different for 5fps and 10fps (as you could expect).
My measurements also show, that these delay can be measured quite reliably in Windows 2000 or Windows XP with precision better than +/-25ms.
So, it is possible to determine time of contacts during transits or occulations quite precisely. The only requirements is to have set exact time in a PC or at least to know the time shift between real time and computer time.


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Last Update: 11.08.2004