So a f/1.8 on a 1" sensor would still gather more light than a f/3.5 on an APS-C?

Bob A L wrote:

As I said in my original response

So you want to go in circles, having learned nothing. You just repeat the same errors, without having taken on board any of the numerous corrections you have had supplied to your mis-statements.

Don't think you can say it gathers more light,

You think wrong. At f/3.5 on the APS-C and f/1.8 on the 1", with same scene luminance and same shutter speed, the 1" captures 1/3 stop more light. If you use ISO 100 on the 1" and ISO 400 on the APS-C you get the same image lightness.

but as far as exposure is concerned, f1.8 is going to work better in low light than f3.5.

For the same sensor, sure, but not if the sensor using f/3.5 is at least twice as large as the sensor using f/1.8.

Sensor format does not affect exposure,

No, but exposure is irrelevant to OP's question. You've been asked why you keep bringing up exposure as a factor in a reply to OP, but all you've told us is that you care about exposure and don't care about noise. You haven't provided a coherent explanation about why you care about exposure when you don't care about noise.

It should be clear from the formulation of OP that OP doesn't share your concerns. It seems OP understands that wanting to achieve the same exposure on different formats is silly.

it only sometimes allows you to use a higher iso to compensate for the slower f3.5 aperture.

There is no "only sometimes". You can always raise ISO above base to compensate lightness for lower exposure used to get similar DOF on a larger sensor.

400 iso on apsc might be as clean as 100 iso on 1". But I doubt that.

ISO 320 would be but ISO 400 would be a third of a stop short.

Looks like you would need to use iso 400 on the 3.5 lens with apsc compared to 100 iso on the 1" at f1.8.

To get the same lightness, yes.

Also dof looks to be slightly deeper in favor of the 1" sensor at these aperture settings.

Nope. Don't know why you are repeating that false claim. DoF is 1/3 stop shallower on the 1".

All in what you are looking for and which things are most important. The larger sensor will usually be expected to provide a bit more image quality at the same settings.

But he's talking about using different settings, as any reasonably knowledgeable photographer would when using two different formats with lenses that have different max apertures.

But things start to vary when you start changing things like max available aperture. If light allows you to close down from max, the picture changes again.

So if settings change there are visible changes to the resulting photo? Profound!