Improving Microscopy Experiments – Sensitivity Vs. Frame Rate in Low Light Imaging

A camera’s sensitivity often impacts its ability to run at its maximum speed, and therefore plays a key role when selecting a digital microscope camera for applications where a live preview in real time is vital, such as electrophysiology.

Frame Rate

There is a direct correlation between the camera’s exposure time and its frame rate: the maximum attainable frame rate in frames per second (fps) cannot surpass 1 divided by the exposure time in seconds. For instance, if the maximum frame rate of a camera is 30 fps but the exposure time is set to 100 ms to obtain a sufficiently bright image, it will be impossible for the camera to run at that frame rate.

The following video demonstrates that the camera could not run faster than 10 fps as it is limited by the exposure time:

Exposure Time

The user may be inclined to increase the exposure time even longer with even less light, further impacting the frame rate. Other mechanisms are also in place to help compensate for dimly lit specimens, but they too have drawbacks.

For example, it is possible to increase the camera’s gain in order to compensate for low light instead of increasing the exposure time. However, an increase in the gain results in an increased noise level, decreasing the accuracy and quality of the image.

Increasing the level of light cast onto the specimen is another way of shortening exposure time so as to not impact the camera’s frame rate. Even though this solution may sound very simple, it may not always be possible in applications such as phase contrast and dark field microscopy.

This solution is also not suitable for other situations, including when the maximum lamp brightness is already being used or when extremely bright light cannot be used for risk of damaging the specimen in live cell microscopy, such as in vitro fertilization.

The selection of an objective with a higher numerical aperture (NA) could also allow for additional light to make its way to the camera; however they may not be available in the required magnification. Additionally, high NA objectives can be considerably expensive, especially when multiple objectives are required.

Sensitivity

Sensitivity is a feature that should be closely observed when selecting a high speed microscope camera. The higher the camera's sensitivity, the less light is needed for each frame. This means that a highly sensitive camera will be able to run at its maximum frame rate under difficult conditions more so than a camera with less sensitivity.

Lumenera’s INFINITY-EP

INFINITY-EP from Lumenera is a low-cost, low-noise, high-speed camera with exceptional sensitivity to suit customers requirements. This camera provides a frame rate of 30 fps at full resolution with incredibly low noise and zero lag, and it also has the potential to work in harsh lighting conditions without compromising frame rate.

This information has been sourced, reviewed and adapted from materials provided by Lumenera Corporation.

For more information on this source, please visit Lumenera Corporation.

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