What is flash duration of a built in flash camera ?

  • Thread starter Thread starter Ray T
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Ray T

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Hi users,

I had a Canon G7, 10MP, 1/2500, ISO 1600, ....

I did the following tests:

The Grinder spins at 3,600 RPM (Revolution Per Minute)
3,600 RPM = 60 RPSecond
or Â*1 Revolution per 1/60 second
or 1/20 Revolution per 1/1,200

1st test
I took a picture with T = 1/1,200, Flash = OFF (a bright light pointed Â*
on the spinning wheel)
The camera could NOT freeze the grinding wheel.
I saw a band of the dots that I marked on the wheel, which is normal.
The picture of a wheel moved 1/20 revolution (an arc of 18 degrees)

2nd test:
Set my camera at T = 1/60, F = 1/2.8, ISO = Auto, FLASH = ON
How can the grinding wheel frozen with this SLOW Shutter speed (1/60)
(sorry, I could not attach the frozen wheel picture below)

Please notes that T = 1/1,200 is 20 times faster than 1/60.
The built in FLASH must be involved.
I guess the wheel turned 1 degree in the picture.
Then the FLASH DURATION must be 1/60 x 360 times faster = 1/21,600.

Does my built in FLASH flash that fast ?!?
(the manufacture did not mention/give out data of the flash duration)

Any clues or explanation ?

Thanks,
 
You seem to be doing a scientific investigation using amateur tools. Don't expect much. Using an optical microscope when you really need an scanning electron microscope will get you no where.

Things to consider.

1) the flash sync shutter speed for the camera you are using.
2) understanding that most on-board flash units are TTL and determining the length of time of the flash is controlled by a sensor in the camera, near the focal plane that determines when enough light has struck the "film" or senor in this case.
3) Talk to a scientific photographer. What they do is use a stroboscope with the lights turned off and the shutter held open. Then they take a series of exposures with the stroboscope regulated at different flash durations.

As you may have guessed, you are using equipment that is making your take more difficult.

At least get hold of a SLR or DSLR and shoot in the dark and adjust the distance of the cameras focal plane to the grinder so you can control the speed of a hand held TTL flash by varying the total distance from the flash tube to the focal plane by moving either or both the flash and camera

Take perfect measurements of those distances and you will get somewhat closer to your goal
 
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