ISO vs Boosted ISO

bobn2 · Jan 4, 2018

D Cox said:
Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

Click to expand...

The ISO setting in a digital camera is not like the number printed on a film carton, because all sensors have an ISO speed of roughly 100 (they do vary slightly). There are no 25 or 400 ISO sensors, unlike films.

Strictly, a sensor does not have an 'ISO' at all, since an 'ISO' can only apply to a rendered image in a defined colour space (very strictly, in sRGB). The question really is what is the largest exposure that a sensor can accept. Since an ISO sets a range of exposures down from 'saturation' (78/ISO lux seconds) then the largest exposure determines what is the lowest ISO it can be used with, if you don't want to lose highlights. In fact, there are plenty of sensors that could be used with 25ISO, they just aren't used in commercial digital still cameras.

bobn2 · Jan 4, 2018

beatboxa said:
bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'. The ISO standard does not mandate how the standardised results should be achieved.

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out, so if you want a brighter image from less light you need to 'amplify' or 'scale' the input. This is wrong. What is coming out of a camera is not 'light', it is grey scale (or at least a three colour primary version of grey scale). Think of what a camera is doing as painting by numbers. The sensor measures exposure pixel by pixel. The camera then chooses a (virtual) paint tone to go with each of those numbers. To get a brighter image, you don't have to amplify or scale anything, you just choose a different palette.

Click to expand...

Xasan · Jan 4, 2018

bobn2 said:
Xasan said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'.

Click to expand...

Most of the cases boosted ISO are achieved differently from the ISO values in the standard range. That's what sets them apart.

Click to expand...

But even that is a simplification.

"Even"? OK.

bobn2 said:
Essentially, every ISO setting is achieved 'differently' from every other one.

How much differently makes some difference.

bobn2 said:
If 'boosted ISO' means anything at all, then the definition, the ones the company doesn't sanction with an ISO number is about the only one that makes sense.

That's rather moot, for example Canon sanctions boosted ISO with numbers in camera specs, like this:

Expanded L (ISO 50), H1: 51200, H2: 102400

Expanded is more or less the standard term across manufacturers. What they say is expanded, maybe. Sometimes they say nothing, just silently scale.

bobn2 said:
If the difference truly was that 'amplification' is achieved by analog means in one case and digital means in the other

Often the case, but intermediate ISO may also be achieved that way, Canon does that.

bobn2 said:
then digital 'amplification' is noiseless, and therefore 'boosted' ISOs are better than 'non-boosted' ones.

I don't follow you, sorry. I never brought noise to the discussion.

bobn2 said:
bobn2 said:

bobn2 said:

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out,

Click to expand...

I don't believe that cameras are putting the light out.

Click to expand...

LOL

--
Tinkety tonk old fruit, & down with the Nazis!
Bob

beatboxa · Jan 4, 2018

bobn2 said:
beatboxa said:

I agree that the concepts of ISO and how ISO is achieved should be separated.

One simple argument of why these should remain distinct concepts would be in ISO invariance: one could argue that all ISO invariant sensor ISOs other than base are boosted.

Click to expand...

Well strictly, as was pointed out to me a long time ago by Iliah Borg, and was of course completely correct, there is no such thing as a 'sensor ISO'. 'ISO' only applies to the output of a complete 'digital still camera'. All this flows from the fact that ISO isn't an input 'sensitivity'. If it's a 'sensitivity' at all, it's an 'output sensitivity' (which is the term ISO actually uses, but needs to be carefully unpicked if not to cause severe misunderstandings).

Fair comment. Just using these terms because otherwise it's hard to describe.

bobn2 said:
bobn2 said:

I'd much rather see ISO 100, 200, 400, etc. rather than ISO 100, Hi-1, Hi-2, Hi-3, etc.

I'd also much rather see where a manufacturer claims max ISO--because this tells a lot about how much electronic noise manifests itself at the high-ISO end.

Click to expand...

I think, on balance, 'ISO', as a tool in digital camera exposure management, is a dead end. Personally, I would prefer if we did away with the film emulation UI (maybe a digital native UI could be offered as an alternative so that people who really feel that they must hang on to the the film emulation UI).

Xasan · Jan 4, 2018

bobn2 said:
beatboxa said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'. The ISO standard does not mandate how the standardised results should be achieved.

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out, so if you want a brighter image from less light you need to 'amplify' or 'scale' the input. This is wrong. What is coming out of a camera is not 'light', it is grey scale (or at least a three colour primary version of grey scale). Think of what a camera is doing as painting by numbers. The sensor measures exposure pixel by pixel. The camera then chooses a (virtual) paint tone to go with each of those numbers. To get a brighter image, you don't have to amplify or scale anything, you just choose a different palette.

--
Tinkety tonk old fruit, & down with the Nazis!
Bob

Click to expand...

I agree that the concepts of ISO and how ISO is achieved should be separated.

One simple argument of why these should remain distinct concepts would be in ISO invariance: one could argue that all ISO invariant sensor ISOs other than base are boosted.

Click to expand...

Well strictly, as was pointed out to me a long time ago by Iliah Borg, and was of course completely correct, there is no such thing as a 'sensor ISO'. 'ISO' only applies to the output of a complete 'digital still camera'. All this flows from the fact that ISO isn't an input 'sensitivity'. If it's a 'sensitivity' at all, it's an 'output sensitivity' (which is the term ISO actually uses, but needs to be carefully unpicked if not to cause severe misunderstandings).

ISO is the way to relate the RAW numbers to output lightness. Same RAW numbers obtained at the same exposure and same camera ISO setting can be related to different output ISO values, depending on the needs.

Sony ISO 800 output sensitivity in Slog mode is implemented via programmed ISO 100 with extra RAW data processing and special mode of converting RAW data to output.

bobn2 said:
bobn2 said:

I'd much rather see ISO 100, 200, 400, etc. rather than ISO 100, Hi-1, Hi-2, Hi-3, etc.

I'd also much rather see where a manufacturer claims max ISO--because this tells a lot about how much electronic noise manifests itself at the high-ISO end.

Click to expand...

I think, on balance, 'ISO', as a tool in digital camera exposure management, is a dead end. Personally, I would prefer if we did away with the film emulation UI (maybe a digital native UI could be offered as an alternative so that people who really feel that they must hang on to the the film emulation UI).

--
Tinkety tonk old fruit, & down with the Nazis!
Bob

bobn2 · Jan 4, 2018

Xasan said:
bobn2 said:

beatboxa said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'. The ISO standard does not mandate how the standardised results should be achieved.

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out, so if you want a brighter image from less light you need to 'amplify' or 'scale' the input. This is wrong. What is coming out of a camera is not 'light', it is grey scale (or at least a three colour primary version of grey scale). Think of what a camera is doing as painting by numbers. The sensor measures exposure pixel by pixel. The camera then chooses a (virtual) paint tone to go with each of those numbers. To get a brighter image, you don't have to amplify or scale anything, you just choose a different palette.

Click to expand...

Click to expand...

Click to expand...

Porky89 · Jan 4, 2018

Alex Ethridge said:
I want to thank everyone for their answers. A lot of it flies right over my head; but, at least some does get absorbed. I think I have at least absorbed enough to know I want to avoid boosted when possible for better IQ.

For the time being, that works for me.

And thank you for your interesting and eminently practical question - and for instigating a particularly entertaining competitive display by DPRs resident amateur scientists all eager to show off to each other.

bobn2 · Jan 4, 2018

Xasan said:
bobn2 said:

Xasan said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'.

Click to expand...

Most of the cases boosted ISO are achieved differently from the ISO values in the standard range. That's what sets them apart.

Click to expand...

But even that is a simplification.

Click to expand...

"Even"? OK.

Was it not a simplification?

Xasan said:
Xasan said:

Essentially, every ISO setting is achieved 'differently' from every other one.

Click to expand...

How much differently makes some difference.

Sometimes, sometimes not. But it isn't a disclosed difference, one that has to be

Xasan said:
Xasan said:

If 'boosted ISO' means anything at all, then the definition, the ones the company doesn't sanction with an ISO number is about the only one that makes sense.

Click to expand...

That's rather moot, for example Canon sanctions boosted ISO with numbers in camera specs, like this:

Expanded L (ISO 50), H1: 51200, H2: 102400

Xasan said:
Expanded is more or less the standard term across manufacturers. What they say is expanded, maybe. Sometimes they say nothing, just silently scale.

Yup, but whether 'expanded' means anything at all is a different matter. At the low end it often (though not universally) means that the sensor doesn't have sufficient saturation capacity to catch the highlights, so you'd better use it for scenes without highlights. At the high end, there is no clear meaning at all. What I mean by 'sanctioned' is that they don't feel able simply to declare it as 51200 (taking your example above). Taking your way of looking at it, what is the 'difference' between the achievement of 25600 and 51200 (in most Canon cameras there will be none, except maybe the addition of involuntary NR - which could actually be Canon's unacknowledged internal definition)

Xasan said:
Xasan said:

If the difference truly was that 'amplification' is achieved by analog means in one case and digital means in the other

Click to expand...

Often the case, but intermediate ISO may also be achieved that way, Canon does that.

Once again, it depends on what you mean by 'achieving' an ISO. Output image production at every ISO setting involves a computational translation from measured exposure values (aka raw) to lightness values. Changing the numbers in that computation does not at all change the nature of that computation.

Xasan said:
Xasan said:

then digital 'amplification' is noiseless, and therefore 'boosted' ISOs are better than 'non-boosted' ones.

Click to expand...

I don't follow you, sorry. I never brought noise to the discussion.

No, I did. The question is, if one want to find a definition for 'boosted' ISO (apart from marketing departments' sophistry) then it exists as a somewhat pejorative term, which is strange, since it should be better.

MarshallG · Jan 4, 2018

beatboxa said:
MarshallG said:

First, the higher the ISO, the lower your image quality.

BUT....
New cameras do and excellent job through at least ISO 800 and even 3200 or 6400 can look great

AND... the quality of the light and your exposure matters more than the ISO. You can get noise at ISO 100; you can get noise in dark areas and it doesn’t matter what the ISO is. Post processing with your computer can filter out a lot of noise artifacts if you have them.

Last... you have to shoot, shoot, shoot and learn how different ISO values look on your camera. Just understand that it’s much more about the quality of light than the ISO setting.

Click to expand...

How do people still believe this about ISO?

For a given exposure, the higher the ISO, the higher the quality. Lower ISO simply allows you to expose more, which is what really leads to higher quality, not the lower ISO itself.

Case in point: from your equipment list, it looks like you have a Canon 5Div. Below, let's compare the ISO's for a given exposure. On the left, you'll see ISO 100; and on the right, ISO 6400:

ISO 6400 is cleaner than ISO 100.

But what ISO 100 allows you to do is to expose higher. This is the root cause of the better image quality, not the ISO.

This goes back to my digital vs. film workflow: In film, you set ISO first, then expose, then process--so your exposure is already limited by the film's ISO.

In digital, you can expose first, then set ISO--which moves the overexposure limit to that of the base ISO.

Yeah, but they make this stuff called “artificial lighting.” You should look into it. Or you could hold the camera steadily and open the shutter, use a faster lens, etc. I didn’t say anything incorrect; I think you just look at things in only one way and everything else seems to upset you.

In my experience, test images don’t reflect the real world. It helps you compare cameras, but image noise and quality, in my experience, have more to do with the quality and nature of the light.

I’ve shot concert photographs at ISO 36,000 which I was very happy with and landscapes at ISO 100 which had noise I was very unhappy with. I don’t think technology or test charts will ever change that fundamental aspect of photography.

To be clear, I bought a 5D and a fast prime lens to provide the best results with indoor, ambient-lit concert photography, and it definitely helps. But if the character of the lighting is bad, the photo won’t be great.

Porky89 · Jan 4, 2018

bobn2 said:
Porky89 said:

bobn2 said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

You are getting the standard answers, only one is right, it means whatever the manufacturer wants it to mean. Generally, the numbered ISO range are those that give what the manufacturer thinks is acceptable quality. The un-numbered one (Hi-1, etc) are ones where the manufacturer isn't prepared to put their name to the ISO setting, but lets you have it any way.

The answer that 'boosted ISO' is when 'amplification' stops is quite wrong, but you hear it frequently, because many digital photography web sites give out this false information. Intrinsically, ISO has nothing to do with 'amplification'. It simply has to do with determining an output image brightness for a given exposure. However, the engineers who design cameras do generally make an internal property called 'voltage gain' change over some part of the ISO range. Sometimes they also change a property called 'conversion gain' (it's a tell-tale sign of a Sony sensor these days). Both those changes have to do with optimising the camera electronics for the expected exposure, they are not 'ISO'. It is rarely the case that the range of ISOs over which the voltage gain is changed matches the range which the manufacturer puts ISO numbers on.

Click to expand...

Click to expand...

bobn2 · Jan 4, 2018

Porky89 said:
Alex Ethridge said:

I want to thank everyone for their answers. A lot of it flies right over my head; but, at least some does get absorbed. I think I have at least absorbed enough to know I want to avoid boosted when possible for better IQ.

For the time being, that works for me.

Click to expand...

And thank you for your interesting and eminently practical question - and for instigating a particularly entertaining competitive display by DPRs resident amateur scientists all eager to show off to each other.

As opposed to the distinctly non-entertaining and tiresome display of DPR's resident buffoon.

Anyway I for one am a professional scientist, not an amateur one, and I would guess that a fair number of the other participants here are also.

bobn2 · Jan 4, 2018

Porky89 said:
" 'Conversion gain' is certainly not a form of 'amplification'. Yes, voltage gain is 'amplification', " - Bobn2

Indeed, that is the case. Explain why you would think otherwise.

(of course, furnishing an explanation would involve you knowing what conversion gain is, which could be a problem for you).

beatboxa · Jan 4, 2018

MarshallG said:
beatboxa said:

How do people still believe this about ISO?

For a given exposure, the higher the ISO, the higher the quality. Lower ISO simply allows you to expose more, which is what really leads to higher quality, not the lower ISO itself.

Case in point: from your equipment list, it looks like you have a Canon 5Div. Below, let's compare the ISO's for a given exposure. On the left, you'll see ISO 100; and on the right, ISO 6400:

ISO 6400 is cleaner than ISO 100.

But what ISO 100 allows you to do is to expose higher. This is the root cause of the better image quality, not the ISO.

This goes back to my digital vs. film workflow: In film, you set ISO first, then expose, then process--so your exposure is already limited by the film's ISO.

In digital, you can expose first, then set ISO--which moves the overexposure limit to that of the base ISO.

Click to expand...

Yeah, but they make this stuff called “artificial lighting.” You should look into it. Or you could hold the camera steadily and open the shutter, use a faster lens, etc. I didn’t say anything incorrect; I think you just look at things in only one way and everything else seems to upset you.

In my experience, test images don’t reflect the real world. It helps you compare cameras, but image noise and quality, in my experience, have more to do with the quality and nature of the light.

I’ve shot concert photographs at ISO 36,000 which I was very happy with and landscapes at ISO 100 which had noise I was very unhappy with. I don’t think technology or test charts will ever change that fundamental aspect of photography.

To be clear, I bought a 5D and an f/1.8 lens to provide the best results with indoor, ambient-lit concert photography, and it definitely helps. But if the character of the lighting is bad, the photo won’t be great.

Artificial lighting, longer shutter speeds, and larger apertures all count as "more exposure," as I clearly explain in this post . You should look into that. Here it is again for your convenience:

MarshallG said:
MarshallG said:

So for the best image quality, always capture as much light as possible first (aperture, shutter speed, or scene lighting) without overexposing at your camera's base ISO (usually 100).

Click to expand...

Your very first statement that I was responding to was incorrect, and is the wrong way to think about digital photography. It's a relic from the film age.

MarshallG said:
First, the higher the ISO, the lower your image quality.

MarshallG · Jan 4, 2018

Xasan said:
MarshallG said:

First, the higher the ISO, the lower your image quality.

Click to expand...

Wrong.

It's a mystery why people keep saying that.

I say it because it’s true. You can use a higher ISO, or you can open your lens. You can use a higher ISO, or a lower shutter speed. You can use a higher ISO, or use a flash. You can move your subject to where the light is more pleasing. There are all sorts of alternatives to increasing ISO. Otherwise, I’d almost always shoot 1/1000 and f/5.6 and use ISO 256,000 or whatever.

My statement is only false if you hold every other parameter constant.

beatboxa · Jan 4, 2018

MarshallG said:
Xasan said:

MarshallG said:

First, the higher the ISO, the lower your image quality.

Click to expand...

Wrong.

It's a mystery why people keep saying that.

Click to expand...

I say it because it’s true. You can use a higher ISO, or you can open your lens. You can use a higher ISO, or a lower shutter speed. You can use a higher ISO, or use a flash. You can move your subject to where the light is more pleasing. There are all sorts of alternatives to increasing ISO. Otherwise, I’d almost always shoot 1/1000 and f/5.6 and use ISO 256,000 or whatever.

My statement is only false if you hold every other parameter constant.

When you open your lens, use a longer shutter speed, or add scene lighting, you're changing exposure, not ISO.

This may come as a surprise to you, but ISO & exposure can be controlled separately. Surprise!

Increased exposure is the cause of improved image quality in the scenario you're describing, not decreased ISO. In fact, as long as you don't clip, you'll get even better image quality if you raise the ISO as well as increase the exposure.

bobn2 · Jan 4, 2018

MarshallG said:
Xasan said:

MarshallG said:

First, the higher the ISO, the lower your image quality.

Click to expand...

Wrong.

It's a mystery why people keep saying that.

Click to expand...

I say it because it’s true. You can use a higher ISO, or you can open your lens. You can use a higher ISO, or a lower shutter speed. You can use a higher ISO, or use a flash. You can move your subject to where the light is more pleasing. There are all sorts of alternatives to increasing ISO. Otherwise, I’d almost always shoot 1/1000 and f/5.6 and use ISO 256,000 or whatever.

My statement is only false if you hold every other parameter constant.

I thin k the point is, that the choice is between using a large exposure or using a smaller one. 'ISO' doesn't change your exposure choices, it just makes your image appropriately processed for the exposure that you choose, and might also optimise the camera for a smaller exposure (though you still won't get as good results as with the bigger exposure).

Xasan · Jan 4, 2018

bobn2 said:
Xasan said:

bobn2 said:

beatboxa said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'. The ISO standard does not mandate how the standardised results should be achieved.

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out, so if you want a brighter image from less light you need to 'amplify' or 'scale' the input. This is wrong. What is coming out of a camera is not 'light', it is grey scale (or at least a three colour primary version of grey scale). Think of what a camera is doing as painting by numbers. The sensor measures exposure pixel by pixel. The camera then chooses a (virtual) paint tone to go with each of those numbers. To get a brighter image, you don't have to amplify or scale anything, you just choose a different palette.

--
Tinkety tonk old fruit, & down with the Nazis!
Bob

Click to expand...

I agree that the concepts of ISO and how ISO is achieved should be separated.

One simple argument of why these should remain distinct concepts would be in ISO invariance: one could argue that all ISO invariant sensor ISOs other than base are boosted.

Click to expand...

Well strictly, as was pointed out to me a long time ago by Iliah Borg, and was of course completely correct, there is no such thing as a 'sensor ISO'. 'ISO' only applies to the output of a complete 'digital still camera'. All this flows from the fact that ISO isn't an input 'sensitivity'. If it's a 'sensitivity' at all, it's an 'output sensitivity' (which is the term ISO actually uses, but needs to be carefully unpicked if not to cause severe misunderstandings).

Click to expand...

ISO is the way to relate the RAW numbers to output lightness. Same RAW numbers obtained at the same exposure and same camera ISO setting can be related to different output ISO values, depending on the needs.

Click to expand...

Strictly,

If you say so.

bobn2 said:
ISO is a way to relate exposure to output lightness. Raw numbers are effectively a measure of the exposure at the pixel (though non-standardised and camera dependent)

ISO implementation mechanism is roughly a 2-part game, one is light input to RAW numbers, the other is RAW numbers to lightness.

Raw numbers relation to exposure is through the first part of ISO implementation. There are few guidelines as to the latter, and none strict.

It is easy to obtain close enough RAW numbers for different exposures of the same scene.

bobn2 said:
bobn2 said:

Sony ISO 800 output sensitivity in Slog mode is implemented via programmed ISO 100 with extra RAW data processing and special mode of converting RAW data to output.

Click to expand...

More accurately,

If you say so.

bobn2 said:
via the same read chain configurations as the ISO 100 settings.

Changes in digital correlated double sampling and green channel averaging necessary for Slog mode currently happen in the read pipeline, but yes, they can be pushed forward, at least in theory.

bobn2 said:
Whether or not Sony Slog conforms to the ISO standard, I don't know.

--
Tinkety tonk old fruit, & down with the Nazis!
Bob

Xasan · Jan 4, 2018

Porky89 said:
" 'Conversion gain' is certainly not a form of 'amplification'. Yes, voltage gain is 'amplification', "

Correct.

Do you amplify you bitcoins converting them to dollars?

D Cox · Jan 4, 2018

beatboxa said:
MarshallG said:

First, the higher the ISO, the lower your image quality.

BUT....
New cameras do and excellent job through at least ISO 800 and even 3200 or 6400 can look great

AND... the quality of the light and your exposure matters more than the ISO. You can get noise at ISO 100; you can get noise in dark areas and it doesn’t matter what the ISO is. Post processing with your computer can filter out a lot of noise artifacts if you have them.

Last... you have to shoot, shoot, shoot and learn how different ISO values look on your camera. Just understand that it’s much more about the quality of light than the ISO setting.

Click to expand...

How do people still believe this about ISO?

For a given exposure, the higher the ISO, the higher the quality. Lower ISO simply allows you to expose more, which is what really leads to higher quality, not the lower ISO itself.

The point here is "for a given exposure". Practically always, you increase the ISO number in order to reduce the exposure.

beatboxa said:
Case in point: from your equipment list, it looks like you have a Canon 5Div. Below, let's compare the ISO's for a given exposure. On the left, you'll see ISO 100; and on the right, ISO 6400:

ISO 6400 is cleaner than ISO 100.

More noise reduction.

beatboxa said:
But what ISO 100 allows you to do is to expose higher. This is the root cause of the better image quality, not the ISO.

This goes back to my digital vs. film workflow: In film, you set ISO first, then expose, then process--so your exposure is already limited by the film's ISO.

In digital, you can expose first, then set ISO--which moves the overexposure limit to that of the base ISO.

I have never changed the ISO number for a shot after taking it. You would have to edit the EXIF data, I think.

bobn2 · Jan 4, 2018

Xasan said:
bobn2 said:

Xasan said:

bobn2 said:

beatboxa said:

bobn2 said:

Xasan said:

Alex Ethridge said:

Most all of my understanding of ISO comes from the days of film.

I see in camera specifications on DPR ISO, Boosted ISO (minimum) and Boosted ISO (maximum).

What does "boosted" mean?

Click to expand...

Those are implemented with some extra steps or non-standard manipulations down the image processing pipeline, often it is digital scaling.

Click to expand...

There are no 'non-standard manipulations'. The ISO standard does not mandate how the standardised results should be achieved.

The root fallacy that these very common but incorrect ideas of what ISO is are based on an idea that what a camera is doing taking light in and putting light out, so if you want a brighter image from less light you need to 'amplify' or 'scale' the input. This is wrong. What is coming out of a camera is not 'light', it is grey scale (or at least a three colour primary version of grey scale). Think of what a camera is doing as painting by numbers. The sensor measures exposure pixel by pixel. The camera then chooses a (virtual) paint tone to go with each of those numbers. To get a brighter image, you don't have to amplify or scale anything, you just choose a different palette.

Click to expand...

Click to expand...

Click to expand...

Click to expand...

Click to expand...

ISO vs Boosted ISO

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