People are very wrong about the advantage of larger sensor

You often hear people say that the low light performance is better with larger sensor. Manufactures and retailers all advertise saying something like “The low light performance is great due to camera's large sensor.” etc.

From physics point view, sensor size actually is irrelevant in low light performance. In the low light situation, the performance is dominated by lens which is independent of sensor. The bigger the lens, the more light it gets, the better IQ.

The true advantage of larger sensor is in the other end of the case, i.e. when light is abundant, one can shoot with base ISO and small aperture. The larger pixel, in this case, can hold more photons and less likely to get saturated, therefore it gives more dynamic range and better color depth etc. The analogy is like this, you drive a 4 tons truck (large sensor), the other guy drive a 2 tons pickup (smaller sensor) to get, say sand (photons). If there is only 1 ton of sand (photons) available, which is limited by supplier (lens), your bigger truck will not have any advantage.

The actual advantages of larger sensor lies in two areas:

1. Resolution - the large sensor can simply fit more pixels.

2. Base ISO performance.

Then why people get the misconception that large sensor has better low light performance? This is simply because the larger sensor camera is often come with larger lens and it is often referred to FF camera, which has many large and bright lenses to select. However, this can not be extrapolated to MF cameras. For example the latest Fuji GFX 50S does not have equivalent bright lens as FF. Therefore, the Fuji GFX 50S does not have any advantages in low light performance in comparison with FF.

So for those who want to “upgrade” to larger sensor cameras, I have a few advices for you:

1. Get as high pixel count as you can. Forget about 24MP FF camera with a f2.8 lens since a 24MP APS-C camera with a f2 lens can match you pixel by pixel.

2. Get fast lenses and use them. Lenses like f1.4, f1.2. Or you just carrying extra weight for nothing.

3. Shoot at base ISO and print image large. You will appreciate the IQ and enjoy the fact that smaller sensor cannot truly match.

Happy Shooting Everyone.

yfan wrote:

You often hear people say that the low light performance is better with larger sensor. Manufactures and retailers all advertise saying something like “The low light performance is great due to camera's large sensor.” etc.

yfan - They say that because larger sensors have better noise performance than smaller sensors due the increased amount of light collected.

From physics point view, sensor size actually is irrelevant in low light performance. In the low light situation, the performance is dominated by lens which is independent of sensor. The bigger the lens, the more light it gets, the better IQ.

There are hundreds of posts explaining the reason for the noise advantage of large sensors. Great Bustard can tell you why you are wrong.

I currently own (in order of preference) -

Canon full frame and APS-C cameras. Similar capability / era cameras.

Sony full frame and APS-C cameras. VERY similar capability / era cameras.

Nikon full frame and APS-C cameras. Similar capability / era cameras.

I've tried this little unspecific experiment WAAY back after buying my Canon 6D. Used the same lens, VERY similar lighting, same subject, same distance on both full frame and APS-C versions of each brand noted above. The full frame cameras pictures won every time...ISO related noise wise. Set the aperture manually, let the camera pick the ISO and shutter speed. Why this method/camera setting...because this is the same way I capture most all of my photo's.

Mike

P.s. - Sold my Pentax, not  good choice of lenses..!

Camley wrote:

yfan wrote:

You often hear people say that the low light performance is better with larger sensor. Manufactures and retailers all advertise saying something like “The low light performance is great due to camera's large sensor.” etc.

yfan - They say that because larger sensors have better noise performance than smaller sensors due the increased amount of light collected.

From physics point view, sensor size actually is irrelevant in low light performance. In the low light situation, the performance is dominated by lens which is independent of sensor. The bigger the lens, the more light it gets, the better IQ.

There are hundreds of posts explaining the reason for the noise advantage of large sensors. Great Bustard can tell you why you are wrong.

In low light case, the SNR is dominated by statistics noise i.e. photon counting, other noise sources such as device's reading noise are negligible.   It is this post's point that those hundreds posts are wrong.  They are still misleading many people like you.  I know what I am talking about.  I have a Ph.D degree in Physics.

My experience* is that FF digital has better performance at ISO 6400. I shoot 1 inch, m4/3 and FF digital. I have a number of indoor portraits at high ISO in my gallery. Here is a shot done with a FF camera held overhead shooting over a crowd.

OOC Jpeg

DXO from RAW

*I do not have a PhD in Physics. I have shot sports, news, commercial, done my own b&w negatives, b&w prints, color slides, color prints. I have shot 35 film, 6X6 film and 4X5 film.

Mike - wrote:

I currently own (in order of preference) -

Canon full frame and APS-C cameras. Similar capability / era cameras.

Sony full frame and APS-C cameras. VERY similar capability / era cameras.

Nikon full frame and APS-C cameras. Similar capability / era cameras.

I've tried this little unspecific experiment WAAY back after buying my Canon 6D. Used the same lens, VERY similar lighting, same subject, same distance on both full frame and APS-C versions of each brand noted above. The full frame cameras pictures won every time...ISO related noise wise. Set the aperture manually, let the camera pick the ISO and shutter speed. Why this method/camera setting...because this is the same way I capture most all of my photo's.

Mike

P.s. - Sold my Pentax, not good choice of lenses..!

I am not surprised you get that conclusion.

You do not know how to interpret your data correctly.

Your FF is getting twice light than your APS-C.  Therefor at the same f-number, ISO the FF is always one stop better.   You have to control the ISO/aperture making sure they get the same amount of total light.

This is mostly right, except it's not the bigger pixels, but rather the bigger sensor. Each pixel is a little photon bucket, and image quality is proportional to the total number of photons you can catch in all the buckets combined.

I think the real advantage of larger sensors though is the amount of lens per dollar you can get. I don't think there's a bigger value for the money than something like a 50 1.8G.

in my limited experience full frame always comes away with cleaner pictures at high ISO (i.e. 6400-12800).

JALComputing wrote:

My experience* is that FF digital has better performance at ISO 6400. I shoot 1 inch, m4/3 and FF digital. I have a number of indoor portraits at high ISO in my gallery.

Your experience is right. But you don't really understand the reason.

To be able to shoot at ISO6400, the FF has to gather twice the light than APS-C, The ability to gather that much light is due to larger lens (not sensor). Otherwise, for the same sized lens, APS-C can always shoot at one stop lower ISO to match the IQ. For the same sized lens, APS-C lens is always about 1-stop faster.

*I do not have a PhD in Physics. I have shot sports, news, commercial, done my own b&w negatives, b&w prints, color slides, color prints. I have shot 35 film, 6X6 film and 4X5 film.

That's irrelevant.  You can be a great artist but not an engineer or scientist.

yfan wrote:

You often hear people say that the low light performance is better with larger sensor. Manufactures and retailers all advertise saying something like “The low light performance is great due to camera's large sensor.” etc.

They say that because it is observed in measured controlled testing as well as a massive concentration of anecdotal experience. Observation is more fundamental to science than calculation.

From physics point view, sensor size actually is irrelevant in low light performance. In the low light situation, the performance is dominated by lens which is independent of sensor. The bigger the lens, the more light it gets, the better IQ.

Yes, in theory, but there are a lot of factors in body/lens design that might impact the end result. The larger sensor bodies may simply afford engineering in them that smaller sensor bodies do not have. You could be correct in not attributing this to the sensor size itself, but at the end of the day, when you buy a camera+lens in the store, the end result matters more than which component is specifically responsible for those results.

The true advantage of larger sensor is in the other end of the case, i.e. when light is abundant, one can shoot with base ISO and small aperture. The larger pixel, in this case, can hold more photons and less likely to get saturated, therefore it gives more dynamic range and better color depth etc. The analogy is like this, you drive a 4 tons truck (large sensor), the other guy drive a 2 tons pickup (smaller sensor) to get, say sand (photons). If there is only 1 ton of sand (photons) available, which is limited by supplier (lens), your bigger truck will not have any advantage.

The actual advantages of larger sensor lies in two areas:

1. Resolution - the large sensor can simply fit more pixels.

2. Base ISO performance.

Not going to agree/disagree on this because its beyond my training, but it sounds reasonable to me.

Then why people get the misconception that large sensor has better low light performance? This is simply because the larger sensor camera is often come with larger lens and it is often referred to FF camera, which has many large and bright lenses to select. However, this can not be extrapolated to MF cameras. For example the latest Fuji GFX 50S does not have equivalent bright lens as FF. Therefore, the Fuji GFX 50S does not have any advantages in low light performance in comparison with FF.

If I cannot buy the equivalent larger lenses for the smaller sensor, then why does this distinction matter when I am making a purchasing decision? When I use the largest/brightest FF lenses on an APS-C body, I still get measurably lower IQ (particularly in lowlight) than a FF sensor. So is it a misconception?

So for those who want to “upgrade” to larger sensor cameras, I have a few advices for you:

1. Get as high pixel count as you can. Forget about 24MP FF camera with a f2.8 lens since a 24MP APS-C camera with a f2 lens can match you pixel by pixel.

2. Get fast lenses and use them. Lenses like f1.4, f1.2. Or you just carrying extra weight for nothing.

3. Shoot at base ISO and print image large. You will appreciate the IQ and enjoy the fact that smaller sensor cannot truly match.

Happy Shooting Everyone.

Agree with this advice, and I am happy with my APS-C setup. That said, in a cost-neutral world, I would still aspire to have the largest sensor platform that also had lenses in the focal lengths and apertures that supported my creative goals.

Regardless of the reason, in practice a larger sensor will give you more options in low light conditions. You can choose higher speed, or lower ISO, or narrower aperture than you can with a smaller sensor in the same environment; assuming you have the same threshold for image quality. If you don't care about image quality, than the discussion is moot.

The proposition that a larger sensor yields better image quality in low light conditions has been proven many times over.

Just no. Way too simplistic, riddled with assumptions.

alanr0 wrote:

yfan wrote:

Camley wrote:

yfan wrote:

From physics point view, sensor size actually is irrelevant in low light performance. In the low light situation, the performance is dominated by lens which is independent of sensor. The bigger the lens, the more light it gets, the better IQ.

But you can't increase the aperture of the lens indefinitely. There is a theoretical limit of F/0.5 (Numerical Aperture 1.0) for a lens in air. For general photographic purposes, there are few lenses faster than F/1.2.

A large sensor allow one to use a large diameter fast lens which can capture more light than is possible with a smaller sensor.

I don't see this conflict with what I said.

There are hundreds of posts explaining the reason for the noise advantage of large sensors. Great Bustard can tell you why you are wrong.

In low light case, the SNR is dominated by statistics noise i.e. photon counting, other noise sources such as device's reading noise are negligible. It is this post's point that those hundreds posts are wrong. They are still misleading many people like you. I know what I am talking about. I have a Ph.D degree in Physics.

Low light is the only regime where device read noise is significant. At higher light levels, photon statistics dominates.

It's SNR matters, not absolute noise level matter.

For equivalent exposures (same field of view, same physical aperture, same shutter speed), the total light collected is indeed independent of sensor size. However a larger sensor allows one to use a physically larger lens whose equivalent either does not exist or is unaffordable for an APS-C sensor.

No argument on this. I acknowledged this by saying that "normally large sensor come with large lens".

Cheers.

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Alan Robinson

alanr0 wrote:

yfan wrote:

To be able to shoot at ISO6400, the FF has to gather twice the light than APS-C, The ability to gather that much light is due to larger lens (not sensor). Otherwise, for the same sized lens, APS-C can always shoot at one stop lower ISO to match the IQ. For the same sized lens, APS-C lens is always about 1-stop faster.

What do you mean by the same sized lens? Same physical aperture or same relative aperture? Same focal length or same field of view?

"same size" is a simplified/approximate state try to make point clear, however, I think it may did opposite.  In general, for equivalent lens on different sensor size, they will end up about the "same" size.   For example, FF 50mm f2.8 is about the same size as DX 35mm f2.    Yes, yes, you will argue that this is not always the case.   The point I try to make is that the low light performance is lens dominated, not sensor.  Going larger and larger sensor does not bring in advantages, MF or large format sensor (if exist) will not give you low light performance.  You need the right lens!  It is a misconception that large sensor equals better low light performance.

If I am shooting with a 50 mm f/1.2 lens on FF, I need a 33 mm f/0.8 lens to capture the same amount of light in the same field of view using an APS-C sensor.

If it exists, the f/0.8 mm lens needs to be more complex to realise 1.5x higher spatial resolution across the frame at increased numerical aperture, so will be bigger, heavier and much more expensive for equivalent performance.

Furthermore it is unlikely that the same effective quantum efficiency would be maintained in current APS-C cameras at f/0.8. Modern sensors rely on micro-lenses to maintain a high effective fill-factor, and these are typically less effective at apertures wider than F/1.4.

Don't get me wrong, I did not deny large sensor's advantages.  I just state that it's irrelevant in low light.  It is lens' that determine the low light performance.  Large sensor responsible for higher resolution and base ISO performance, etc.

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Alan Robinson