# FPS to Hertz in a camera

Not sure if this is the proper place to ask this, but I'm sure someone here will know the answer.

I have this optical camera (TrackIR 4), which, for what you can see on the table, samples images at a rate of 120 frames per second.

Now how would you do a conversion from fps to Hertz to find out the frequency rate at which the camera samples data?

Maybe it's a stupid question, but I wanna make sure I get the right value.

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## 1 Answer

The physical definition of frequency is the number of oscillations per second and measured in Hertz (Hz) or more general: 1/(duration of one period of a periodic event in seconds). In your case the periodic event is a frame and it occurs 120 times per second so the frequency is 120 Hz.

If you want to find out the sampling frequency of the ADC device in the camera you could calculate it like that: $$f_\mathrm{s} = N_\mathrm{pixel} \cdot R_\mathrm{frame}$$ where $N_\mathrm{pixel}$ is the number of pixels in the sensor and $R_\mathrm{frame}$ is the frame rate. With the numbers from the data sheet I obtain a sampling frequency of 12.3 MHz. I can't tell if this is the actual frequency used by the camera. If it uses oversampling or interlacing the value could differ.

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Okay, I guess 120 is the number I was looking for (and my first guess, also). Thanks! –  kelmer Nov 12 '12 at 16:47