Login  Register

Re: Eastimation signal to noise ratio on imageJ

Posted by Michael Schmid on Oct 24, 2017; 8:12am
URL: http://imagej.273.s1.nabble.com/Eastimation-signal-to-noise-ratio-on-imageJ-tp5019580p5019596.html

Hi RL,

the background level and noise are two different quantities.
Noise means fluctuations, i.e. signal components that are different from
image to image.

To measure the dark and readout noise, take two dark frames (i.e. images
with the camera shielded from light), subtract them (Image Calculator
with '32-bit' result), measure the standard deviation and divide by sqrt(2).
If you vary the exposure time, you can also differentiate dark current
noise and readout noise (in the limit of zero exposure time, you have
only the readout noise).

You can also measure the noise under illumination conditions: take two
images with *exactly* the same camera position and illumination,
subtract them (make sure that the result contains no image information
any more!). Again, take the standard deviation of the result and divide
by sqrt(2). This noise includes the shot noise of the photons.


Michael
________________________________________________________________
On 22/10/2017 17:18, thpnick688 wrote:

> Hi, everyone,
>       I have encountered a question on estimating signal to noise ratio on
> imageJ. I have an image with 4x4 binning. The binning is done by the CCD
> detector not by the software. I use the ROI to measure the mean gray level
> intensity on the main object in the image. I also use the same size ROI on
> the background to measure the background noise. I use the simple equation
> "S/N= “mean gray level intensity in subject” / “mean gray level intensity of
> the noise”" to estimate the signal to noise ratio. However, by comparing
> with an image that is unbinned, I didn't see the SNR is improved after the
> calculation. So, what mistakes did I make?
>
> RL
>
>
>
> --
> Sent from: http://imagej.1557.x6.nabble.com/
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html