Aperture v Sensor Size for lowlight

[Hippo_MC]

Cant get my head round what would be better for lowlight photography. I think I have a basic grasp on aperture, ISO & shutter speeds, but can't work out what is better for an advanced compact, fast lens or bigger sensor?

For example, if all things were equal (forgetting whether one camera is better than the other.

If I was to have ISO set at 400ISO, focal length at 100mm.

If I was to use the Canon G15 with aperture at 2.8 (sensor size 1/1.7) or use the Sony RX100 with aperture at 4.9 but sensor size at 1"

I presume shutter speed as an example for the 2.8 might be 1/500 where as the shutter speed for the 4.9 would be 1/200.

I presume that if I go into full manual, I am going to be able to more handheld shots in low light with the faster lens, if I stick with 2.8 and slow the shutter speed a little?

Have I got this right? :bonk:

 

[viewfromthenorth]

If by 'better' you mean less noise, then a bigger sensor wins. But if you are handholding, then yes a faster lens allows faster shutter speeds, but not as high as in your examples. A bigger sensor has no impact on this.

 

[rjbell]

The g15 hasn't been tested at dxo yet but using the g12 figures noise starts to be noticeable at iso 160 the rx100 iso 390 so just over 1 stop advantage, but the lens on the g12 is almost 2 stops faster by your figures so shooting wide open the canon would have the advantage. Hopefully the g15's iso performance will be better than the g12 too.

 

[Nawty]

Sensor size has nothing to do with exposure so forget about that to start with and it should all become clear.