What Is A Camera Sync Test
Camera Sync Tester User Guide
Content
- Introduction
- Command Line Parameters
- Using Photographic camera Sync Tester
- Case
- Choosing Resolution and Refresh Rate
Introduction
The Camera Sync Tester software (click here to download) has been developed to measure the mis-sync of two or more video cameras using a CRT monitor's electron axle equally reference motion. Knowing the mis-sync of cameras is, for example, important when taking stereoscopic photos or recording stereoscopic videos using ii cameras.
Measuring mis-sync is commonly done past recording a well known motion so that the time offset between a pair of images can be calculated subsequently, based on dissimilar stages of motion. Real moving objects are difficult to handle. Information technology is much simpler to use a CRT monitor's electron axle equally reference motion instead.
Important: This article was written a few years ago when CRT monitors and CCDs with global shutter were common. The method described does not work with LCDs. When testing cameras with CMOS sensors, the rolling shutter effect might interfere with the measurement method.
Control Line Parameters
| -x | Horizontal screen resolution |
| -y | Vertical screen resolution, limited to 768 pixel |
| -f | Refresh rate |
Example: Synctest.exe -x1024 -y768 -r100 runs the Photographic camera Sync Tester at a resolution of 1024 10 768 pixel at 100 Hz.
Using Camera Sync Tester
To measure the mis-sync, run the Camera Sync Tester and capture the screen using the cameras under test. Effort to keep the exposure fourth dimension of both cameras as curt as possible. Delight annotation that only CRT monitors can be used for this purpose, LCD displays don't work!
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| Test pattern shown by Photographic camera Sync Tester. After each refresh cycle, the number of vertical confined is increased. |
Later on, analyze corresponding frames taken from the kickoff and 2nd camera. In each frame, you lot see the position of the monitor's electron beam, simply usually this position will be different for the frames of the first and 2nd photographic camera (except they are 100% in sync). The difference of the final visible lines corresponds to the mis-sync. Depending on the exposure time, more than one line volition be visible. We strongly recommend to utilise the positions of the bottom lines for doing the calculations, because these are the ones drawn almost recently (the tiptop lines are fading away, so at that place will exist no sharp border).
For the following calculations, we need the monitor's current horizontal (fHoriz ) and vertical (fVert ) refresh rates. Your monitor's on-screen carte du jour will tell y'all these value. The time the electron axle needs to depict i line is:
tLine = ane / fHoriz
The time the electron beam needs to describe a whole frame is:
tFrame = 1 / f Vert
To calculate the mis-sync tBeginning , we multiplay tLine with the difference of the terminal line numbers zane and ztwo visible in the left and right image:
tBeginning = (z2 - zi ) / fHoriz
If left and correct frames practise non show the same number of vertical confined (bane , b2 ) then the mis-sync is greater than the elapsing of i screen refresh cycle! In this case, one or more screen refresh cycles (tFrame ) must be added to the previous upshot.
tGet-go = (z2 - zi ) / fHoriz + (b2 - bi ) / fVert
The Camera Sync Tester package includes an Excel spreadsheet which allows to evaluate the results of multiple measurements conveniently.
Example
Take a wait at the image to a higher place. As you lot can see, the right image was recorded slightly earlier, since the electron beam has merely reached line z1 = 223 whereas it is already at line z2 = 403 on the left epitome. Both images where taken during the same refresh cycle because the number of vertical bars are equal (b1 = b2 = ii).
In our example, the screen was set up to the standard VGA mode at 60 Hz (fHoriz = 31.5 kHz, fVert = 60 Hz) while taking the images. Don't confuse horizontal and vertical frequencies. The horizontal frequency fHoriz is always college than the vertical frequency, which is usually in the range of 60 - 200 Hz.
tOffset = (403 - 223) / 31500 Hz + (ii - ii) / 60 Hz = v.7 ms
Choosing Resolution and Refresh Rate
What resolution and refresh rates should exist used? For videos, the default settings, 640 10 480 pixel at 60 Hz are sufficient. A higher resolution does non brand sense because you would non exist able to distinguish lines anymore. A higher refresh rate does non brand sense either. However, if you lot want to measure the mis-sync of your high resolution stereo photograph camera, a higher resolution could make sense.
Source: https://www.3dtv.at/Knowhow/Synctest_en.aspx
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