Signal to Noise Ratio & Noise Exposure Calculator
Signal to Noise is an important parameter that can be used to compare how a camera may perform compared to another model or under different conditions. This calculator tool lets you select and compare selected camera models and adjust options such as exposure time. The data may be exported as a csv file for further analysis. It must be remembered that while such calculators are useful it is of course, recommended, where possible, to demo cameras under the real-world experimental conditions.
- Select a pre-defined camera from the Camera Type Drop down list. Note that you may adjust values for a custom camera, or per the unique values for your camera that may be found on the supplied Performance Sheet.
- Add an extra camera using the Add Camera button
- Adjust the exposure time as required – the default is 1 second.
- Compare the Signal to Noise ratio in the displayed graph. Note that you may compare on a per pixel basis as Plot as Photons / Pixel, or per unit area as Plot as Photons / 13 µm2
- Dark current - sensor operational temperature affects dark current and may become important if the camera is not cooled and/or at longer expsoures– ensure that this matches with the temperature you intend to run your camera at.
- Read Noise - an ideal camera would have 0 read noise. However the readout process from a sensor generates a certain amount of noise. This may vary with readout mode. EMCCD cameras are often considered to have effectively zero read noise.
- ENF – this additional Extra Noise Factor applies to EMCCD cameras only and is due to the EM amplification itself.
- QE – the quantum efficiency is a measure of the probability that a photon that arrives at the sensor will turn into an electron that can subsequently be digitized and amplified so it may form an image.
- Pixel size – as a general rule a larger pixel will have a better sensitivity as the larger area means more chance that a photon will be detected. However a smaller pixel may provide better spatial resolution of an image and is relevant at lower magnifications. Therefore when comparing on a per pixel basis you would need to correct for pixel size of the different cameras. For example, a camera with a smaller pixel would need a longer exposure time to collect the same number of photons as a larger pixel for the same illumination intensity.
- Camera Type – a range of pre-defined cameras may be selected including an ideal camera with 0 noise. This is a useful reference point to have.
- Signal : Noise – here signal is plotted by the standard equation: Noise = ENF x ((QE x no of photons) + ReadNoise2 + (Texp x IDark))1/2
- In practice, front illuminated cameras sCMOS will have a detection limit in the region of 10-20 photons per pixel. Back-illuminated sCMOS cameras will provide extended sensitivity within this region. EMCCD cameras will provide sensitivity down to single photon levels.
- To learn more about calculating the signal to noise ratio click here