Small sensors gather less light? Wrong!

[TrojMacReady]

Firstly, 14% difference in pixel pitch is practically negligible.

If you feel that falls within the margin of error for measurement as done by for example DXO, I challenge you to back that up with some math.

Secondly, you're comparing sensors of different resolution.

Ofcourse, that's the only way to compare the effect of pixel pitch.

Thirdly, you're comparing sensors of the same size.

Ofcourse, see above.

We are discussing smaller sensors with finer pixel pitch.

We are discussing smaller sensors. Pixel pitch does not have a negative effect and should not accordingly be used in the argument.

So if you want to convince me, compare a 12 Mpix sensor with 300% (which is still moderate) greater pixel pitch than another 12Mpix sensor.

Why are you ignoring the links I provided that systematically and thoroughly explain the issue to you providing visual examples aswell?

 

[TrojMacReady]

PS: we are not talking about the (number of pixels: pixel pitch) ratio for a given sensor size.

we are talking about different sized sensors at roughly the same resolutions.

Did you actually have a look at the links I provided? (for example a comparison of 2 10MP cameras with a dramatical difference in pixel pitch).

 

[Chippy99]

I think there is a certain amount of talk at cross-purposes going on.

The amount of light falling on a sensor depends on the effective diameter of the lens (not aperture number), the loss when passing through the glass elements and filters and the proportion of the light cone occupied by the sensor.

The efficiency of photon capture by the sensor is another issue. I think the OP was more concerned about a geometric missconception when talking about the size of sensors.

Actually it also depends on the focal length. Concentrating the light onto a smaller chip requires a shorter focal length and therefore a lower f-stop, ie. a faster lens.

I had overlooked this originally.

That said, my original point is still valid. All we are talking about is glass with a slightly higher degree of curvature. It doesn't need to be massive piece of glass.

 

[JanKritzinger]

Secondly, you're comparing sensors of different resolution.

Ofcourse, that's the only way to compare the effect of pixel pitch.

Thirdly, you're comparing sensors of the same size.

Ofcourse, see above.

HOW RETARDED ARE YOU?
this discussion is about SMALLER SENSORS.

SMALLER SENSORS with the SAME RESOLUTION have FINER PIXEL PITCH.

OF COURSE higher resolution offsets the drawbacks of finer pixel pitch, but in a smaller sensor you can't increase the resolution.

 

[TrojMacReady]

If what you're saying is true, a 12mpixel compact would have the same sensor performance as a 12Mpixel Full frame camera, which is simply absurd.

Obviously you missed the fact I stated that sensor AREA is the key. Ofcourse they wouldn't perform the same because the sensor area isnt nearly the same. But the advantage of the full frame camera is unrelated to pixel pitch.

Comparing two aps-c cameras is nothing short of silly.

It's not as pointed out before. But since you fail to actually click on the example I provided earlier, I'll just post it again:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=28607494&q=sheehy+fz50+canon&qf=m

 

[JanKritzinger]

I cba to go through old 100 post threads to look for your 'proof'

Which cameras are you talking about?

 

[TrojMacReady]

Secondly, you're comparing sensors of different resolution.

Ofcourse, that's the only way to compare the effect of pixel pitch.

Thirdly, you're comparing sensors of the same size.

Ofcourse, see above.

HOW RETARDED ARE YOU?

Arguments fail, ad hominem steps in, not unexpected.

this discussion is about SMALLER SENSORS.

Yep.

SMALLER SENSORS with the SAME RESOLUTION have FINER PIXEL PITCH.

Yep but smaller pixel pitch is simply a result. It has no negative influence on noise levels as you suggested. A smaller sensor also results in less weight of the sensor. Should that be used in the argument too? No, it's pretty much irrelevant in the context.

OF COURSE higher resolution offsets the drawbacks of finer pixel pitch, but in a smaller sensor you can't increase the resolution.

Why not?

 

[TrojMacReady]

I cba to go through old 100 post threads to look for your 'proof'

Which cameras are you talking about?

That answers that. It was the first link I provided. That very post.

 

[JanKritzinger]

If what you're saying is true, a 12mpixel compact would have the same sensor performance as a 12Mpixel Full frame camera, which is simply absurd.

Obviously you missed the fact I stated that sensor AREA is the key. Ofcourse they wouldn't perform the same because the sensor area isnt nearly the same. But the advantage of the full frame camera is unrelated to pixel pitch.

You have to be the stupidest person i have ever encountered on the internet.

Read the topic of the discussion.
SMALLER sensors.
a SMALLER sensor, is one having LESS AREA than another.

For two sensors, both of 12MPix, but of different size, the larger one will have coarser pixel pitch, and correspondingly better IQ.

If the better IQ gained from the larger sensor, given an equal number of pixels, is not from increased pixel pitch, WHERE DOES IT COME FROM?

 

[Chippy99]

If what you're saying is true, a 12mpixel compact would have the same sensor performance as a 12Mpixel Full frame camera, which is simply absurd.

I don't see how that follows.

The 12mpixel compact sensor is receiving less light so obviously it doesn't perform as well.

The question is, how would it perform if it received the same amount of light.

 

[JanKritzinger]

SMALLER SENSORS with the SAME RESOLUTION have FINER PIXEL PITCH.

Yep but smaller pixel pitch is simply a result. It has no negative influence on noise levels as you suggested.

Okay, so why do smaller sensors exhibit poorer performance, if not due to pixel pitch?

 

[JanKritzinger]

If what you're saying is true, a 12mpixel compact would have the same sensor performance as a 12Mpixel Full frame camera, which is simply absurd.

I don't see how that follows.

The 12mpixel compact sensor is receiving less light so obviously it doesn't perform as well.

The question is, how would it perform if it received the same amount of light.

It would still perform poorer due to individual photocells performing poorer due to physical constraints.

 

[TrojMacReady]

If what you're saying is true, a 12mpixel compact would have the same sensor performance as a 12Mpixel Full frame camera, which is simply absurd.

Obviously you missed the fact I stated that sensor AREA is the key. Ofcourse they wouldn't perform the same because the sensor area isnt nearly the same. But the advantage of the full frame camera is unrelated to pixel pitch.

You have to be the stupidest person i have ever encountered on the internet.

Keep up the attitude, it's helping.

Read the topic of the discussion.
SMALLER sensors.
a SMALLER sensor, is one having LESS AREA than another.

Exactly and that's where the differences follow. Not because of pixel pitch as you suggested.

For two sensors, both of 12MPix, but of different size, the larger one will have coarser pixel pitch, and correspondingly better IQ.

No it won't as the example I posted also shows. You keep repeating a myth ignoring facts and examples as provided.

If the better IQ gained from the larger sensor, given an equal number of pixels, is not from increased pixel pitch, WHERE DOES IT COME FROM?

From the larger area ofcourse, as you suggested yourself. So did you actually have a look at the example provided in my previous post?

 

[TrojMacReady]

SMALLER SENSORS with the SAME RESOLUTION have FINER PIXEL PITCH.

Yep but smaller pixel pitch is simply a result. It has no negative influence on noise levels as you suggested.

Okay, so why do smaller sensors exhibit poorer performance, if not due to pixel pitch?

Because the total amount of photons captured is less due to a smaller total area ofcourse.

 

[Dennis]

The brightness (f-number) of a lens tells about the light level over the whole image circle, no matter if the image circle is is covering a narrow or wide area.

You can't gather the light outside the sensor and put this light into the area that is covered by the sensor. I think this is where your idea breaks down.

The more I think about this, I think I am wrong (and you are right) in that what I am really suggesting is lower f-stop lenses.

That said, there is nothing wrong in asserting that with different glass, the small sensor can gather just as much light as a larger one. And in respect of your sentence:

You can't gather the light outside the sensor and put this light into the area that is covered by the sensor. I think this is where your idea breaks down.

Yes you can. Why not.

Think about it this way: if one lens can project a greater light intensity onto a sensor at f/2.8 than another lens can, the whole exposure system breaks down. It only works because light intensity at f/2.8 is constant. (Basically - you might see measurable differences due to coatings, etc, and you have lenses like the 135STF which transmit less light, by design).

• Dennis

--
Gallery at http://kingofthebeasts.smugmug.com

 

[kilobytemachine]

Forgive me posting this here - it's not Sony specific, but I am a Sony user and it will get read more here than in some off-topic forum.

But, this is something I only thought about when waking up this morning. It's a universally accepted truth that small sensors gather less light than larger sensors and the former are therefore not as good in low light conditions, producing more noise in high ISO shots.

Everyone knows this, right? I mean it's obvious. The photocells are smaller and they can capture less photos in a given time compared to larger ones. Obviously.

But this is WRONG.

It would be true if the sensor was waved around in the air naked, but in a camera, it is not. The flaw in the paragraph above is that it should read "The photocells are smaller and they can capture less photos in a given time compared to larger ones, given the same level of illumination " And therein lies the flaw.

The amount of light gathered and available for the sensor is not governed by the sensor, it's governed by the lens . If you focus the light from the lens onto a smaller area, the intensity of light increases as the area gets smaller and smaller - ultimately like a magnifying glass in the sun with a spot that is so bright and hot that it burns paper. But all the light is still there, in the tiny spot. That tiny spot is "seeing" all the photons just as the larger magnifying glass lens front is "seeing" them.

Now, clearly if you put a Canon 50mm f/1.4 on the front of an APS-C sensor, in the focal plane, the APS-C sensor takes up less area than an full frame sensor, and so it is true in that case that the smaller sensor gets less of the light.

So my thoughts maybe true, but of only academic interest in a DSLR where things like the distance from the lens rear element to the focal plane are fixed and determined by the system. The smaller sensor sees less of the lens' light and there's not much can be done about it.

But in a proprietary system like a p&s, everything is up for grabs by the designers. It is perfectly possible to have an APS-C sensor gather exactly the same amount of light as a FF one, but focusing all the available light from the lens onto the sensor. The sensor size does not determine how much light the lens captures, the lens does! Putting a bigger sensor behind the glass would not capture any more light if the smaller sensor was already capturing all the light!

So, given the above is true (and thinking about it, clearly it is), I wonder why the small-sensors-gather-less-light myth persists?

Sure, small sensors enable the use of smaller and cheaper lenses, which then gather less light. But that does not need to be the case. Someone could quite easily design a p&s camera witha 1/1.7" sensor that performed just as well as a A900 in terms of light gathering. Practically speaking, you'd have a massive camera though, because the lens would have to be as large as a FF system lens. So the benefit of having a very small sensor is largely eliminated and there would be little point in the design.

And there maybe other practicle issues that influence sensor performance. I am not an expert, but I would not be surprised if heat in the sensor also produces noise and a smaller sensor will be less able to dissipate heat than a larger one.

But consider this. Canon (or whoever) come out with a new p&s and everyone immediately looks to see if the sensor is 1/2.3" or 1/1.7" in size, because they think the larger sensor must gather more light. But this is just plain wrong. Maybe the smaller sensor gathers more? Who knows. It depends on how the lens has been designed, not on the sensor size.

Bizarre, but true!

You've just described the effect of putting a f/1.4 lense on a crop sensor camera vs a f/2.8 lense on a FF sensor camera. (approximately speaking, depending on crop factor) The exposure would be the same. However, that same 1.4 lense can also be mounted on the FF sensor camera. To receive the same amount of light, the cropped camera would need a f/0.7 lense. Kinda hard to come by those...

No, I haven't, but I can understand the confusion. The f number is the ratio of the entrance pupil diameter over the focal length.

Envisage two lenses with the same entrance pupil and the same focal length. But one focuses all the light perfectly onto an APS-C sensor; the other focuses all the light perfectly onto an FF sensor.

Both sensors receive the same amount of light and both lenses have the same f-stop.

I am not talking about faster lenses to achieve the same amount of light capture.

So what you're saying is it's possible to have two lenses with the same f number and focal length but producing different illumination per unit area?

My apologies, I am wrong about this. I was not thinking it through properly.

A more concentrated image (focussed onto a smaller rather than a larger sensor) must mean a shorter focal length (all other things being equal). i.e. a lower f-number.

I had mistakenly been thinking you could have the same focal length but different "magnification", but this is incorrect.

Apologies once again.

No apologies needed whatsoever. I didn't write the laws of physics. But if ever they were up for review, may i nominate you for the review board? Love your ideas!

 

[JanKritzinger]

If the better IQ gained from the larger sensor, given an equal number of pixels, is not from increased pixel pitch, WHERE DOES IT COME FROM?

From the larger area ofcourse, as you suggested yourself.

I give up. You win. Have a nice day.

 

[TrojMacReady]

If the better IQ gained from the larger sensor, given an equal number of pixels, is not from increased pixel pitch, WHERE DOES IT COME FROM?

From the larger area ofcourse, as you suggested yourself.

I give up. You win. Have a nice day.

I agree the example I linked to was enlightening.

 

[Chippy99]

The brightness (f-number) of a lens tells about the light level over the whole image circle, no matter if the image circle is is covering a narrow or wide area.

You can't gather the light outside the sensor and put this light into the area that is covered by the sensor. I think this is where your idea breaks down.

The more I think about this, I think I am wrong (and you are right) in that what I am really suggesting is lower f-stop lenses.

That said, there is nothing wrong in asserting that with different glass, the small sensor can gather just as much light as a larger one. And in respect of your sentence:

You can't gather the light outside the sensor and put this light into the area that is covered by the sensor. I think this is where your idea breaks down.

Yes you can. Why not.

Think about it this way: if one lens can project a greater light intensity onto a sensor at f/2.8 than another lens can, the whole exposure system breaks down. It only works because light intensity at f/2.8 is constant.

Hmmmm. I am not entirely sure I agree with that.

Consider a lens, say 50mm f/1.4. Hold it in your hand and point it at the window.

Now take a sheet of paper and hold it near the rear element. Move the paper backwards and forwards to and from the rear element. You see the image of the window moving in and out of focus on the paper. But at certain points the image is smaller and brighter, and at others it is larger and less bright.

The light intensity definitely does vary, even with 1 lens, with a fixed f-stop in constant lighting conditions.

I was postulating about a small sensor capturing all of the light by being closer to the rear element. What I had not factored in was that would mean a shorter focal length (in order to keep the image focused) and therefore a lower f-number.

 

[Zamac]

I think there is a certain amount of talk at cross-purposes going on.

The amount of light falling on a sensor depends on the effective diameter of the lens (not aperture number), the loss when passing through the glass elements and filters and the proportion of the light cone occupied by the sensor.

The efficiency of photon capture by the sensor is another issue. I think the OP was more concerned about a geometric missconception when talking about the size of sensors.

Actually it also depends on the focal length. Concentrating the light onto a smaller chip requires a shorter focal length and therefore a lower f-stop, ie. a faster lens.

Not really. Focal length and F-number determin the size of the iris aperture opening. However, it is the iris aperture itself that is the physical determinant of the amount of light entering the camera.

This is wat I meant by talking at cross-purposes - a am agreeing with you even if I express it a little differently.

I had overlooked this originally.

That said, my original point is still valid. All we are talking about is glass with a slightly higher degree of curvature. It doesn't need to be massive piece of glass.