This is something i come across every now and then, so there is this notion that, for example an apsc sensor with a f3.5 lens collects more light than my 1 inch sensor pocket camera at f1.8 which results in lower noise levels and a lower iso used to take the same shot.
Perhaps you are misunderstanding what was said. Can you actually give a link to where somebody said that? The usual, correct, statement is that a larger sensor collects more light at a given exposure.
Basically some say that f1.8 on a 1 inch sensor is equivalent to something like f5.6 on a apsc sensor.
Then they are wrong. F/1.8 on a 1" sensor is equivalent to approximately f/3.2 on an APS-C (Sony/Nikon/Fujifilm) sensor or f/3 on a Canon APS-C sensor. It is also equivalent to about f/4.8 on FF.
In reality though, it's nothing like that. I did my testing.
Yeah it will be nothing like that if they get the equivalency wrong by more than a stop.
A dslr from 2012 with kit lens really struggles to capture the same low light scene where my 2012 sony rx100 has no issue at all, despite the fact that the two should be at least similar. But no. To get the same image i have to use iso 6400 on the larger camera while the rx100 happily uses iso 3200.
ISO 6400 on APS-C should be less noisy than ISO 3200 on 1", if the remaining settings give the same lightness.
My explanation for this comes down to the lens, an kit lens at f3.5/f4 cannot compete against the faster f1.8 lens on the other camera despite having a much smaller sensor.
The sensor is slightly less than two stops smaller, but f/4 collects less than two stops lower light than f/1.8, so of course the 1" does better under those conditions.
If i use a faster lens on the dslr the camera can compete against the rx100 however i lose DoF
A larger sensor only gets a noise advantage by using a shallower DOF, (if the shutter and scene luminance are the same).
and noise levels will be similar even though they shouldn't.
Who says they shouldn't be similar? F/2.8 on the APS-C camera will provide only 1/3 more stop of light than f/1.8 on the 1". That's similar noise. You'd probably get similar noise if the APS-C was at f/2.5.
What i am saying is that in real life, there is no way the larger sensor "gathers" any more light than the smaller sensor even when using equivalent lens.
Then what you are saying is flat out wrong. At the same exposure, a larger sensor gathers more light,. It is hardly a novel discovery that reducing the exposure reduces the amount of light gathered.
Like i said, even if i use f1.8 on both the dslr and the pocket camera, i lose DoF on the larger sensor.
Yes. If the larger sensor doesn't use a shallower DOF (assuming same shutter and scene luminance) it has no noise advantage. It gets that shallower DOF at the same f-number or at any f-number between the same one and the smaller sensor's f-number multiplied by the relative crop factor.
I find that, in practice, one is more often constrained WRT only one of DOF or shutter speed in a single shot. So for most shots, the larger sensor can still capture more light., because it will use the same or similar exposure. For those shots were both DOF and shutter speed are constrained, a larger sensor has no noise advantage.
One of the most common shooting situation is a landscape in good light. We'll assume that f/11 gives the right DOF on a Nikon ZII. On your RX100 VII you'd get the same DOF with f/4. In Sunny-16 light, you'd use settings of {1/2,500, f/4, ISO 125} on your RX100 VII. That high shutter speed is a total waste in a typical landscape, but you have to use it to avoid overexposing. On a Z7 II, I'd use {1/160, f/11, ISO 64}. This gives me the same DOF, but I actually have one stop more exposure, so I have captured 4 stops more light (one stop for the exposure difference & three more stops for the sensor size difference. My shadows will be way less noisy than yours.
This can be a good thing or a bad thing, but generally speaking i prefer more DoF not less.
I prefer just enough DOF. More than that gives more diffraction blur and more noise.
For the reasons stated above i am quite content with the iso results i get from my RX100 VII even with the slow f2.8 lens.
I'm happy that you are content.
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So my conclusion is, F1.8 on a 1 inch sensor results in a noticeably faster camera
It is 1/3 stop faster. I doubt you can actually notice that..
Blurry? Because of a 1/3 stop difference in shutter speed? Or do you mean noisier? It's 1/3 stop less noisy too, Most peeple won't notice that.
than f3.5 on apsc at the same iso and exposure.
Wait! "At the same ISO and exposure"? That means the APS-C camera is using a slower shutter. But why would you use the same exposure on a different format. That's just silly. At the same exposure, the APS-C camera will gather about 4 times as much light
I know this because i've been using kit lenses for more than a decade and getting sharp images even with maxing out the iso(6400 in my case) indoors is a real struggle even with IS kit lens.
So for me, faster lenses have helped me out way more than being able to use a higher iso, and this is regardles of the sensor size(before i was a rx100 user i had a Panasonic LX3, it had a f2 lens coupled to a even smaller sensor).
Faster lenses allow higher exposure and higher exposure is always preferable to raising ISO.
The advantages of fast glass are more relevant in real life than sensor size,
That's not true. If you have a 3-stop difference in sensor size, you'd need a lens that was more than three stops faster to get a better result from the faster lens than from the larger sensor.
and i'm saying this as a current owner or 4 different systems(1 inch sensor, M43 and apsc from Canon and Nikon).
On all these cameras the glass and IS system make the difference, not the sensor size.
On all of these systems, both the glass and the sensor size make a difference.
