Crop factors and lens performance
Photographers often become obsessed with lens speed, particularly when shooting in dim lighting and especially with respect to prime lenses. There’s a good reason for this response: faster lenses allow more light to reach the image sensor, thereby reducing the need to boost ISO settings and allowing faster shutter speeds to be used. This reduces the risk of blurring due to camera shake.
But with modern improvements to sensor performance, stabilisation and autofocusing technology, lens speed becomes less important. There are other factors to take into account, especially the effects the size of the camera’s image sensor can have on the amount of light a lens admits.
The influence of crop factors
Users of digital cameras will be familiar with the influence of the size of the image sensor on the effective focal length of a lens.
