comparing lens + sensor size combos for low light

[FingerPainter]

The equivalent aperture tells you what aperture on a full frame lens would give the same depth-of-field and the same total light as the one you're assessing.

The whole "total light" business is WRONG WRONG WRONG.

Remember that image size changes, so that your "4 times" is spread across a larger area to create the same image on the sensor.

There are other reasons that a larger sensor gives better IQ, but the total amount of light hitting it is NOT the reason.

...

Sorry David, but I believe you are wrong about AHM being "WRONG WRONG WRONG" about total light. An aperture of f/2 on uFT is equivalent to f/4 on FF. The f/4 will produce 1/4 the light intensity of f/2, but on a FF sensor it will be spread over 4 times the surface area, so 4 x 1/4 will give it the same total light as F/2 on uFT

...

Total light is MEANINGLESS. It has no importance to anything and is a derived value. I have no clue why people talk about it as if it is important.

The only thing it does is to show who is clueless.

...

... Total light does matter because it affects image quality. Total light difference is the REASON why a larger sensor is better than a smaller sensor

If you don't understand simple physics, then just be quiet. Please.

...

If it is simple physics, you should be able to explain it, rather than just make unsupported assertions.

So tell us what light is, how it is generated, what noise is, what the sources of noise in a photograph are, describe the importance of shot noise to overall noise levels, explain the circumstances under which the SNR relative to shot noise is high...

C'mon, it is just simple physics - explain it.... if you can.

Maybe you should explain to me how "total light" means anything. Since you guys brought it up first. ...

OK.

Total light means the total number of photons whose impact on the sensor has resulted in a change to the values recorded by the sensor.

An image is a captured signal.

Noise in an image is variation from the ideal signal. The perceptibility of noise is measured by a Signal to Noise Ratio (SNR).

Noise can be measured over a variety of spatial frequencies. One can measure it per pixel, per unit area or per image. The only times these measurements all yield the same value is when the image is composed of one pixel of one unit area, or when the signal is nonexistent. Otherwise, the larger the area over which the noise is measured, the larger the SNR.

For most exposures on modern digital cameras, the most significant source of noise in an image is noise that is already present in the light even before it hits the sensor. This is called shot noise.

Shot noise comes about from the quantum nature of the creation of light. Light is electromagnetic radiation emitted from an atom in response to a rise in the atom's energy state. This radiation can be modelled as either a particle (a photon) or a wave. The wavelength emitted, and the timing of the release of photons is random but dependent upon both the atomic number of the atom and of the level of energy increase. Typically an atom will emit photons at a particular rate and at a particular wavelength, but due to quantum mechanical effects, there will be variations in both the timing of photon release and the wavelengths released. These variations are the shot noise.

While the variations are random, the pattern of variation follows a Poisson distribution. As a result, the SNR of light is equal to the square root of the signal. Therefore the amount of signal in the area over which noise is measured (the total light) directly determines the amount of shot noise.

 

[sybersitizen]

I already said DOF would be different. I qualified "noise" being different because it's much more complicated than just a mathmatical equation.

1. Noise doesn't matter, what matters is apparent noise. Noise you can see. So the subject matters. A lot.

2. light recpetors are imperfect mechanical devices. Therefore they can be better, or worse. Generally, over time, they get better. So a brand new smaller senosr may produce less noise than a much larger sensor from 10 years ago.

It might surprise you that the concept of equivalence can be discussed and understood without any reference to sensor behavior or sensor generations or pixel pitch or read noise or any of the variables that are associated with image capture. This is true because equivalence relationships assume uniform and hopefully perfect performance of the recording medium across all the formats being compared - and uniform and hopefully perfect lenses, too - all of which, of course, are rarely found in the real world. Maybe you missed this post from the previous page, so I'll repost it. It might help:

When the discussion is about equivalence, I find it much better not to think of pixels at all - in fact, not to think of sensors at all. Those things are unnecessary complications that muck up the analysis. I think instead of the actual optical images that are produced by the different formats - or the actual image circles produced by lenses designed for different formats - without the peripheral factors that involve the capture of those images.

Imagine that you are inside a sort of perfect camera obscura and looking at live optical images projected by the camera formats you want to compare. Think about the fact that you will need to somehow adjust the different image sizes to match one another in order to properly discuss equivalence. The only way you could get the smaller image to match the larger one is through some sort of optical enlarging process. Even if you have a perfect enlarging mechanism that preserves every detail, any such process will reduce the overall intensity of the image. That can't be helped... and that will reduce not only the apparent S/N ratio, but also the apparent dynamic range (the brightest areas will be not be as bright as the brightest areas of the larger image, but the darkest - black - areas will be equally dark for both.) Coincidentally, those are two of the improvements that people actually report when they move from smaller to larger formats.

You can instead choose to optically reduce the larger image to make it smaller, which will of course also make it brighter... so you get the same end result anyway in terms of the comparison.

Knowing that an optical enlargement or reduction process must involve those compromises, is it logical to think that a digital capture and digital enlargement or reduction process would be immune to the compromises? If so, how exactly is such immunity achieved?

 

[FingerPainter]

Why is proper exposure relevant ? Gee, I don't know..

You could be right about that.

Exposure affects three aspects of an image:

1. Image brightness,
2. Data discrimination at the DR extremes (clipped highlights and blocked shadows)
3. Shot noise.

Of these, image brightness is the least important, becaus it can be adjuisted in post

The other two are more important because post production cannot reover data \from blown highlights or blocked shadows nor losslessly elliminate noise. Therefore selecting the optimal exposure is a balancing act between reducing shot noise and retainggn shadow and/or highlight detail.

In addition, the two cameras settings that affect exposure each have an additional effect on an image. Shutter speed affects motion blur and aperture affects DFO. So if either of those is a consideration, there may be additional balancing that is required when selecting exposure parameters.

I already said DOF would be different. I qualified "noise" being different because it's much more complicated than just a mathmatical equation.

1. Noise doesn't matter, what matters is apparent noise. Noise you can see. So the subject matters. A lot.

You can't see nose that isn't there. Yes, eh relatie importance of noise to highlights to shadows, to mosion blur top DOF vareis with teh subject.

2. light recpetors are imperfect mechanical devices. Therefore they can be better, or worse. Generally, over time, they get better. So a brand new smaller senosr may produce less noise than a much larger sensor from 10 years ago.

True enough, but a brand new sensor from 10 years in the future is unlikely to produce less noise in a single image than a current large sensor because we are now approaching the physical limits of sensor efficiency. There isn't a full stop of improvement left, but there will always be about a stop of difference between formats because of the effect of sensor size on total light gathered.

 

[FingerPainter]

Yes. However, what is exposure? It's just how much light per unit area is used to draw the image. Different formats have different amount of area, thus the same exposure settings on different formats create a different image.

Thus naturally also to create the same image on different formata you have to use different exposure settings.

In short: exposure is a tool, a mean to an end not the other way around.

ISO is not relevant in this context - it's not an exposure parameter .

Abe R. Ration - amateur photographer, amateur armchair scientist, amaterur camera buff
http://aberration43mm.wordpress.com/

What ? ISO is not an exposure parameter ?

That is the case .

There's two things that determine exposure

Three things.

, amount of light, controlled by aperture and how long the shutter is opened, and the sensitivity of the "film", expressed in a digital camera as ISO setting.

No. Exposure is defined by scene luminance, aperture number and exposure time.

Wikipedia has a nice article on the subjct .

In photography, exposure is the amount of light per unit area reaching image sensor.

The ISO setting does not change the amount of light reaching the image sensor in any way, form or shape.

Also ISO does not change the sensors sensitivity.

It's definitely an "exposure parameter."

Not according to International Organization for Standardization.

And, different formats don't use different exposure settings for the same image.

They do. I think I should clarify things:

First, when I say image I mean the image the lens draws into the image plane unless it is clear from the context I mean something else.

However this is often a bit of a shortcut as the size of the image is naturally different for each format. Often what is meant in this context is the information content of the image (i.e. we ignore the different sizes of the images - that is not relevant in this context).

So to be absolutely clear here:

The information content of the images are different on different formats if the same exposure settings are used, and vice versa, the information content can only be the same on different formats if different exposure parameters are used.

And the information content includes the depth of field and amount of light (and signal to noise ratio).

 

[Abe R Ration]

Information content ? I'm talking about exposure, you know, if a picture is too dark, too light, or just right.

That is not exposure, but brightness. They are very different concepts. Brightness is a function of processing, not a function of exposure. The output image can be of any brightness one wants it to be.

The same aperture, shutter speed, and film sensitivity, will give the same exposure, no matter what size the film is.

Film sensitivity is not part of exposure as I've already shown. Please read the wikipedia page.

I don't care what any organization says,

Indeed. The organization is the one which defines for example ISO sensitivity.

if you shoot with Kodachrome 25, and Tri-x pan 400, you are not going to get correct exposure if you don't adjust your camera for the proper film speed.

And that is still irrelevant to the context.

And I doubt anyone here is arguing that the same exposure itself would somehow magically be different for different formats - certainly I haven't: exposure is simple a function of exposure time, aperture number and scene luminance - the size of the lens or format is not relevant for it.

So there is no need for you to repeat it.

However, the same exposure creates a fidderent effect on different format.

As far as I know, that's what the word "parameter" means.

If you don't like to discuss with standard terminology but instead redefine the metrics to suit your agenda, whatever that is, it is going to be very difficult for you to have a civilized and meaningful discussion on the relevant topics.

 

[Abe R Ration]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

I believe this is the section you are referring to. Quote (http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2):

The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity.

And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image. It's likely that the large sensor camera will be bigger, heavier and more expensive, but it should provide cleaner images.

The flip-side of this is that, if you can fit a faster lens to a smaller format sensor or use a slower shutter speed then you can match the total light available to the larger system and gain similar image quality. However, this only really works in low light, where you're limited by the availability of light. In bright lighting conditions, where you're more worried about highlights clipping than you are about noise swamping the shadows, you can't simply open the aperture up to match a larger sensor's total light - you'll just end up over-exposing.

Yes, exactly. And this statement:

The equivalent aperture tells you what aperture on a full frame lens would give the same depth-of-field and the same total light as the one you're assessing.

That doesn't change anything about exposure. F/2.8 is f/2.8 as far as exposure, no matter what the sensor size is.

If I may step in here - yes the above is right of course, but what is exposure?

To quote wikipedia:

In photography, exposure is the amount of light per unit area reaching image sensor.

Exposure is a useful tool, that's it. It by itself does not tell anything about noise levels or depth of field or other such metrics. The same exposure always creates a different effect for the output image on different formats. Always.

The dof is different. The amount of noise is possibly different. The exposure is the same.

DoF and amount of noise are always differen if the exposure is the same and format is different. Noise (or standard deviation) of light is the square root of signal (or number of photons). The more light you collect, the higher the signal to noise ratio (SNR), or what we perceive as "noise".

As exposure is a "per area" metric, having more area means that more light is collected by the same exposure and if more light is collected the "noise" is lower.

Having more "total light" doesn't change the exposure.

True (assuming it's the format size which changes the total light), but why is that relevant?

For more infomation on comparing formats you can go here .

 

[lumigraphics]

Thus naturally also to create the same image on different formata you have to use different exposure settings.

 

[lumigraphics]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

Yes I used more paint on the bigger wall, but it is spread out across a bigger area, too.

Light and sensors/film work the same way. A bigger sensor absorbs more light for the same exposure, because the light has to be spread out across a larger area.

Correct exposure means that the sensor reproduces the real-life image faithfully (let's define it that way) without losing shadow or highlight details. A smaller sensor collects less total light, but that light is spread across a smaller area, so that exposure is the same and our subject is reproduced correctly.

Anyone who has used a standalone light meter can tell you that there isn't a format adjustment. It measures the light and tells you what ISO setting, aperture, and shutter speed combination will provide correct exposure.

Now, there are certainly a host of other effects from changing format. And digital noise is influenced by sneers size, just like grain was influenced by film size. But trying to say that "total light" means a thing is just simply bullhonky.

 

[sybersitizen]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

One more time: If you're going to discuss equivalence, you have to compare your examples at the same final viewing size.

And what happens when you enlarge the smaller wall to match the size of the larger wall? The paint gets thinner and doesn't cover as well, so the quality of the paint job indeed declines.

You have actually come up with a scenario that supports the ideas you are opposing.

... But trying to say that "total light" means a thing is just simply bullhonky.

'Total light' is a perfectly valid concept in a discussion of equivalence for the reason described above: maintaining the same final viewing size.

If you don't care about final viewing size and are okay with maintaining different final viewing sizes, you are no longer discussing real equivalence... and then 'total light' is unimportant.

 

[FingerPainter]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

Yes I used more paint on the bigger wall, but it is spread out across a bigger area, too.

Light and sensors/film work the same way.

Well, not they don't. With paint, once you get a certain minimum coverage density adding more paint doesn't improve the look of the wall. Addig gmore light does improve the image, by increasing SNR.

A bigger sensor absorbs more light for the same exposure, because the light has to be spread out across a larger area.

That's right. In collecting more ligt it receives a higher signal;. And thus a higher SNR, and thus less perceivable noise.

Correct exposure means that the sensor reproduces the real-life image faithfully (let's define it that way) without losing shadow or highlight details.

Why would we define it that way? Why wouldn't we define it as the exposure that gives us the least noise without losing highlight detail? We can always adjust image brightness in post, but we cannot losslessly adjust out nise.

A smaller sensor collects less total light, but that light is spread across a smaller area, so that exposure is the same

Yes

and our subject is reproduced correctly.

Not necessaruily. And our subject is reproduced with more noise. And if we used the same exposure parameters, it is produced with a different DOF.

Anyone who has used a standalone light meter can tell you that there isn't a format adjustment. It measures the light and tells you what ISO setting, aperture, and shutter speed combination will provide correct exposure.

I'd perhaps put it a little differently. ISO and scene luminance are input parameters to the meter and all possible pairs of shutter speed and aperture that will give realistic brightness for the given ISO are the output parameters.

But why is realistic SOOC brightness the correct result if we can use a different exposure and post processing to get the same brigthness in the final image but with less noise?

Now, there are certainly a host of other effects from changing format. And digital noise is influenced by sneers size, just like grain was influenced by film size. But trying to say that "total light" means a thing is just simply bullhonky.

Total light means amount of shot noise. That is a thing.

 

[FingerPainter]

Thus naturally also to create the same image on different formata you have to use different exposure settings.

 

[Pixel Pooper]

Thus naturally also to create the same image on different formats you have to use different exposure settings.

BZZZZZT.

No, that's not how it works.

Where do you people come up with this stuff?

PING!

Yes, it is.

If you want the same image on different formats, you need to use different apertures to get the same DOF, so you can either change the shutter speed to compensate for the aperture change, or keep the same shutter speed and change your ISO setting. Either way, the exposure settings are different.

 

[semifast]

You can call exposure "image brightness" if you want. As far as I'm concerned there is no distinction.

And it's true you can adjust apparent exposure in post processing, but that doesn't change anything either.

f/2.8 is f/2.8 whether you use a 1 inch square of film, or a 10 foot square. As far as exposure is concerned.

 

[lumigraphics]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

One more time: If you're going to discuss equivalence, you have to compare your examples at the same final viewing size.

And what happens when you enlarge the smaller wall to match the size of the larger wall? The paint gets thinner and doesn't cover as well, so the quality of the paint job indeed declines.

You have actually come up with a scenario that supports the ideas you are opposing.

... But trying to say that "total light" means a thing is just simply bullhonky.

'Total light' is a perfectly valid concept in a discussion of equivalence for the reason described above: maintaining the same final viewing size.

If you don't care about final viewing size and are okay with maintaining different final viewing sizes, you are no longer discussing real equivalence... and then 'total light' is unimportant.

I'm gonna take a wild guess and say that I was shooting large format film before most of you ever took up photography. I'm well-versed in how all this stuff works.

The only thing I can say at this point is that you people are seriously lost in the wilderness. I'll pray to the photo gods for your souls.

Oh and I'll laugh to myself whenever I see another idiotic total light post. And go back to working on improving my photography.

 

[lumigraphics]

Thus naturally also to create the same image on different formats you have to use different exposure settings.

BZZZZZT.

No, that's not how it works.

Where do you people come up with this stuff?

PING!

Yes, it is.

If you want the same image on different formats, you need to use different apertures to get the same DOF, so you can either change the shutter speed to compensate for the aperture change, or keep the same shutter speed and change your ISO setting. Either way, the exposure settings are different.

Who was talking about DOF? You people are going on about exposure. :roll eyes:

 

[sybersitizen]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

One more time: If you're going to discuss equivalence, you have to compare your examples at the same final viewing size.

And what happens when you enlarge the smaller wall to match the size of the larger wall? The paint gets thinner and doesn't cover as well, so the quality of the paint job indeed declines.

You have actually come up with a scenario that supports the ideas you are opposing.

... But trying to say that "total light" means a thing is just simply bullhonky.

'Total light' is a perfectly valid concept in a discussion of equivalence for the reason described above: maintaining the same final viewing size.

If you don't care about final viewing size and are okay with maintaining different final viewing sizes, you are no longer discussing real equivalence... and then 'total light' is unimportant.

I'm gonna take a wild guess and say that I was shooting large format film before most of you ever took up photography. I'm well-versed in how all this stuff works.

The only thing I can say at this point is that you people are seriously lost in the wilderness. I'll pray to the photo gods for your souls.

Oh and I'll laugh to myself whenever I see another idiotic total light post. And go back to working on improving my photography.

Okay - buh-bye!

 

[Pixel Pooper]

lumigraphics wrote:exposure settings are different.
Who was talking about DOF? You people are going on about exposure. :roll eyes:

We people have been going on about equivalence, you are the one who keeps trying to make it about exposure.

 

[jackalopemaui]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

I believe this is the section you are referring to. Quote (http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2):

The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity.

And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image. It's likely that the large sensor camera will be bigger, heavier and more expensive, but it should provide cleaner images.

The flip-side of this is that, if you can fit a faster lens to a smaller format sensor or use a slower shutter speed then you can match the total light available to the larger system and gain similar image quality. However, this only really works in low light, where you're limited by the availability of light. In bright lighting conditions, where you're more worried about highlights clipping than you are about noise swamping the shadows, you can't simply open the aperture up to match a larger sensor's total light - you'll just end up over-exposing.

Yes, exactly. And this statement:

The equivalent aperture tells you what aperture on a full frame lens would give the same depth-of-field and the same total light as the one you're assessing.

That doesn't change anything about exposure. F/2.8 is f/2.8 as far as exposure, no matter what the sensor size is.

The dof is different. The amount of noise is possibly different. The exposure is the same.

Having more "total light" doesn't change the exposure.

Jesus H Christ, why is this so difficult to understand.

RIGHT, the light intensity at the sensor does not change.

HOWEVER, the total light collected by the sensor does change, which affects image quality. ISO 100 on a MFT sensor is equivalent in quality to ISO 400 on a full frame, because one is 4x the size of the other.

Take two solar panels. One is 6ft x 6ft. Another is 3ft x 3ft. The sunlight intensity hitting both is the same. Both are equally sensitive to light. But one is collecting 4x as much sunlight and producing 4x as much power as the other. Doesn't that make sense to you?

In the real world, solar panel size matters. In the real world, sensor size matters. Do you accept these facts or not?

 

[andrewD2]

If I paint two walls, one larger than the other, I have to use more paint on the larger wall. Because its bigger. But the total amount of paint doesn't determine the quality of the paint job.

One more time: If you're going to discuss equivalence, you have to compare your examples at the same final viewing size.

And what happens when you enlarge the smaller wall to match the size of the larger wall? The paint gets thinner and doesn't cover as well, so the quality of the paint job indeed declines.

You have actually come up with a scenario that supports the ideas you are opposing.

That's true, but you've not really got the analysis of his analogy quite correct.

To suggest taking a small section and enlarging it would make the paint spread more thinly is incorrect. To do so would suggest that printing a crop of an image would result in different brightness than printing the whole image at the same size.

If you could scale up the wall, you'd scale up the paint with it.

The difference would be that if you could you scale up the small section (or more likely compare both viewed from distances proportional to the sizes of the wall sections) the brush strokes and imperfections on the smaller section will be coarser and more apparent. That's your 'noise' or 'grain' if the objective is a perfectly smooth coat.

So what we can say is that per unit area the small section and large section are painted just as evenly but when comparing the whole of one to the whole of the other the larger surface looks better.

Andrew

 

[Abe R Ration]

Thus naturally also to create the same image on different formata you have to use different exposure settings.