The short answer to this question is yes, full-frame cameras are better in low light. But, that is not an absolute statement, and it won’t hold true in all circumstances. There are many other factors responsible for creating a digital image, and without accounting for those factors, it wouldn’t be wise to declare full-frame cameras a clear
M43 (crop factor of 2x) base ISO of 200 = Full-frame ISO 800. APS-C (crop factor of 1.5x) base ISO of 100 = Full-frame ISO of 225. All of these smaller sensor sizes (especially APS-C) will look great at base ISO and you probably won't be able to tell the difference when comparing with a full frame image. For example, Nikon often refers to its full-frame cameras as “FX” and their crop sensor cameras as “DX”, while others refer to cameras by sensor size, such as “35mm” and “APS-C”. For now, all this nomenclature does not matter – look again at the first image and see the resulting photographs on the right side of the camera. In this video I see just how much better portraits from a full frame camera (Sony A9) are when you compare them to an APS-C mirrorless camera (Sony A6100). (Sony A9) are when you compare them Full-frame lenses are compatible with APS-C cameras, and Canon’s full-frame RF lenses can be used on its APS-C cameras without the need for an adapter. In doing so, there is a crop which