A slow shutter speed will improve low light performance but cause ghosting images

What is shutter speed used for

The shutter speed of a camera controls how many samples per second the image is captured to the CCD or CMOS sensor. This has nothing to do with the images per second that you view live or record.

How shutter speed is used for low light

In many camera’s they use a ‘slow shutter’, also know as ‘progressive scan’, ‘image summation’ and other names but all meaning the camera samples the image multiple times before sending it to the output.

This means a dark scene can be made to look brighter by taking several images and stacking them to build up the light.
The problem with doing this is if an object is moving, it can appear as a ghost or smear across the scene. Sometimes if it is fast moving, not be seen at all!

I would recommend never using less than 1/12s shutter

If you use too slow a shutter to improve the low light performance, you will not be able to define any detail of a moving object. Even at 1/12 it will not be crisp unless moving slowly.

Using an aspherical lens with have a better (lower) f-stop

A better option to improve low light performance than lowering the shutter speed is to use a faster lens – that is one with a lower f-stop. This is typically achieved with an a-spherical lens.

What is a shutter speed for fast objects like cars

Because increasing the shutter speed means we are processing more images per second, it will eliminate the blur of a car moving by at speed. In my experience, a car at 60km/h will be sharp at 1/125s shutter speed. This is essential for reading number plates in ANPR – Automatic Number Plate Recognition – applications. ANPR is also referred to as LRP and ALPR where L is Licence.

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