Of course ISO is an exposure variable - when you are shooting digital

[Josh152]

Great Bustard wrote:

gollywop wrote:

jrtrent wrote:

tomtom50 wrote:

Fir film cameras exposure is aperture and shutter speed, because those are the dials you twist picture optimally bright balancing what you need for other attributes like dof, sharpness, and blur. Adjusting your camera to get the right brightness balancing the other attributes needed a good strong word because that was an important part of taking good pictures.

Now with digital camera we have three settings to get the right brightness balancing the other attributes. We know have new attributes in the mix, DR, detail, and noise

I like your thinking, but I don't really see much difference between digital and film with these three variables. ISO was still something that was chosen, and for those who used cut film or multiple camera bodies, there was some flexibility from shot to shot--though not as easily as can now be done with digital!

This blurb reflects my use of exposure and ISO:

Exposure determines how much light gets to the film. All still cameras have two fundamental controls for this: lens aperture and shutter speed. The combination of the two is the exposure value, or EV used for exposure. Film speed (discussed later) determines the quantity of light that will properly expose the film. The combination of film speed and the brightness of the scene determine an EV that can be translated into specific combinations of aperture and shutter speed to capture the proper quantity of light. http://johnlind.tripod.com/science/scienceexposure.html

Good usage is usage that successfully communicates the relevant information, and becomes widespread. Technology changes and the words meanings change as well. That's why we dial phone numbers on phones that have no dials.

Good point. And a concept of exposure that includes three variables instead of two makes good sense to a lot of picture takers, some of whom have become quite famous and even written books using this idea. The "exposure triangle" has helped several people I know to get the results they want a much higher percentage of the time.

Yes, but they could have been helped just as well with a "brightness triangle" and come away with a better and more accurate idea of what they were doing.

Thing is, "brightness triangle" doesn't sound cool like "exposure triangle". I mean, would you rather say you're the trash man or say you're a sanitary engineer? ;-)

I was thinking the same thing. At some point "exposure" became kind of a status word. People who self identify as Photographers like to talk about a photos "exposure" because it makes them sound and more importantly feel more technical and savvy than their non photographer friends who talk about how a photo is too bright or too dark.

 

[Gerry Winterbourne]

gollywop wrote:

You continue to be in error.

exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

The medium is always assumed; what is in question is which factors are in play (and which are not). That question is answered directly with the part that says exposure is defined as:

Hv = Ev .t

where

• Hv is the luminous exposure (usually in lux seconds)
• Ev is the image-plane illuminance (usually in lux)
• t is the exposure time (in seconds)

By any rational use of English exposure time, as opposed to exposure duration, should mean not how long the exposure was but when it was taken. But, of course, this is pedantry gone mad. Everyone knows that exposure time can have different meanings depending on context. After all, that's true of a lot of expressions.

Indeed, it's true of exposure too. There's nothing wrong with the definition you quote here and it's fine in the context for which it is intended. But, like exposure time, exposure has other meanings depending on context. It isn't an error, as you suggest, to use a term in a different context from the one you happen to prefer.

The logic failure in my title refers to the idea of thinking that exposure can only have one meaning while defining it by reference to a term that can have multiple meanings - if all terms must have just one meaning the definition itself is wrong; or multiple meanings are fine.

 

[Lee Jay]

Sammy Yousef wrote:

ljfinger wrote:

Sammy Yousef wrote:

ljfinger wrote:

Exposure controls the amount light that hits the sensor (the "brightness" [illuminance - controlled by f-stop] times the time [controlled by shutter speed]). ISO is just the "volume control" applied to that exposure after it has been taken.

If that were true there would be no difference between one exposure boosted after the fact, and another taken at a higher ISO. In fact there is.

Only because Canon sensors have high read noise. On sensors with constant read noise, there isn't.

You're talking about an ISO-less camera? Show me market penetration of isoless cameras and I'll agree.

What does market penetration have to do with it? Besides, several of the Nikon and Sony cameras have this.

This is literally true - the ISO settings is used only after the shutter is closed and the exposure is complete. It's used either during the readout process or during the digital processes after that.

It is used in the readout process which is affects what is actually recorded.

And after the exposure has been taken - after the shutter is closed. And, in some cases, it's just multiplying the digital data by a constant, which could be done later.

There is a difference between boosting sensitivity during reading and boosting it afterwards. The recorded information is different and is not equivalent.

Maybe, maybe not. Regardless, some cameras don't boost the analog amplification when you change ISO, at least at some ISOs. Neither of my SLRs do above ISO 1600, for example, and neither do a couple of my compacts at any ISO.

 

[Leon Wittwer]

Yes. In the days of film, getting the exposure right was a more difficult proposition and took considerable skill and judgment. There was no "chimping" and taking several shots was costly so getting it right the first time was important. There was considerable prestige for those who could get the "exposure" right.

 

[bobn2]

hjulenissen wrote:

bobn2 wrote:

gn-aus wrote:

In reading some of the replies to this and similar posts it appears that all those writers who refer to the 'exposure triangle' have all got it wrong?

That is essentially the core of the controversy. Many photographers were 'educated' with the 'help' of the exposure triangle. I don't know who invented it, maybe it was Petersen - but whatever, it has been extensively copied. And yes, it is wrong. Not just wrong, but actually quite damaging to understanding, as are many faulty educational 'aids'.

A strict definition of exposure may well exclude ISO, but for practical purposes, in the digital age, it clearly is part of the decision options.

Not so clearly, and not always. But the major point is that the exposure triangle leads to a faulty assumption, that raising ISO is the same as raising exposure, even Petersen makes that mistake, as do several 'experts' who peddle the exposure triangle.

 

[gollywop]

Gerry -0 wrote:

gollywop wrote:

You continue to be in error.

exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

The medium is always assumed; what is in question is which factors are in play (and which are not). That question is answered directly with the part that says exposure is defined as:

Hv = Ev .t

where

• Hv is the luminous exposure (usually in lux seconds)
• Ev is the image-plane illuminance (usually in lux)
• t is the exposure time (in seconds)

By any rational use of English exposure time, as opposed to exposure duration, should mean not how long the exposure was but when it was taken. But, of course, this is pedantry gone mad. Everyone knows that exposure time can have different meanings depending on context. After all, that's true of a lot of expressions.

Indeed, it's true of exposure too. There's nothing wrong with the definition you quote here and it's fine in the context for which it is intended. But, like exposure time, exposure has other meanings depending on context. It isn't an error, as you suggest, to use a term in a different context from the one you happen to prefer.

The logic failure in my title refers to the idea of thinking that exposure can only have one meaning while defining it by reference to a term that can have multiple meanings - if all terms must have just one meaning the definition itself is wrong; or multiple meanings are fine.

Pedantry of the most errant kind.

The time is stated to be given in seconds. Such a criteria is completely meaningless relative to time of day since no origin is given, and even if one were, the resulting figure would have no immediate meaning to anyone.



--
gollywop

 

[bobn2]

gollywop wrote:

Such a criteria is completely meaningless relative to time of day since no origin is given

If we're being pedantic, that should be 'such a criterion' ;-)

 

[gollywop]

bobn2 wrote:

gollywop wrote:

Such a criteria is completely meaningless relative to time of day since no origin is given

If we're being pedantic, that should be 'such a criterion' ;-)

Ouch! Ya' got me. One demerit for today. ;-)

--
gollywop

 

[yardcoyote]

Exactly. I am a digital newbie and one of the things I am finding exciting, and very challenging, is the new role of ISO in the whole exposure dynamic. It was always there, but now that you can change it in every shot it is a new factor in decision making. That's what exposure always meant to me-- a set of decisions you make so that the correct amount of light falls on the picture plane to create the image you want.

The fact that a set of definitions originally used with film may need to be expanded to cover the needs of a new technology is hardly the end of the world. Nor is it the end of the world for an English word to have two definitions, even two technical definitions within the same field. You can have "exposure: film photography" and "exposure: digital photography" without harming the English language one bit. That's how English works. It's the original big tent.

If you want to blow your mind, consult the definition of the word "set" in an reputable unabridged dictionary. It's a noun, it's a verb, it has perhaps a dozen definitions in everyday use, plus technical terms in fields like mathematics, and nobody seems to get upset about it.

 

[bobn2]

yardcoyote wrote:

Exactly. I am a digital newbie and one of the things I am finding exciting, and very challenging, is the new role of ISO in the whole exposure dynamic. It was always there, but now that you can change it in every shot it is a new factor in decision making. That's what exposure always meant to me-- a set of decisions you make so that the correct amount of light falls on the picture plane to create the image you want.

The fact that a set of definitions originally used with film may need to be expanded to cover the needs of a new technology is hardly the end of the world. Nor is it the end of the world for an English word to have two definitions, even two technical definitions within the same field. You can have "exposure: film photography" and "exposure: digital photography" without harming the English language one bit. That's how English works. It's the original big tent.

Sure, but there is a problem with your brave new world. The definition of 'ISO' (including the digital versions of ISO) depends on the definition of 'exposure'. So, if you include 'ISO' within the definition of 'exposure', you have a logical contradiction that you cannot escape. If you want a way out, you'd need to propose to the 'ISO' how they could define exposure index without using exposure (could be hard)

 

[tkbslc]

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

And here we are with a camera that has an ISOless sensor:

http://www.dpreview.com/forums/post/37235114

If we did the same with a camera that had a non-ISOless sensor, the pushed ISO 100 photo would be more noisy.

As "we" have been saying, the ISO setting is a matter of pre-processing the light that falls on the sensor, and, as such, is not an element in exposure, but an element in processing.

Thus, your challenge, and my answering that challenge, is irrelevant in terms of what exposure is and isn't.

If you had taken that shot with the same ISO and reduced shutter speed by 6 stops and then brightened it with RAW editing software, you'd have the same shot, too.

No, you'd have a rather different photo. You'd have a photo that was made with 64x (6 stops more) light. Big difference.

reducing the shutter speed decreases the light, but either way, I corrected for it with the RAW editor, just as those pushing the ISO do.

Apologies -- I misinterpreted "reduced shutter speed" and was thinking the exact opposite. In any case, the photos in the link above were shot with the same camera and exposure, thus the same amount of light and thus the same noise.

Your idea of reducing the shutter speed, and thus reducing the light, would make for a much more noisy photo.

In theory, anyway.

 

[tkbslc]

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

The camera controls that affect exposure are the aperture, shutter speed, and flash power -- period. Yes, the ISO setting indirectly affects these settings depending on the AE (Auto Exposure) mode you are using, but the ISO setting itself is not an element of exposure. In short, do not confuse correlation with causation (for example, thinking that the calendar is what causes the seasons).

I don't think flash power directly affects exposure anymore than the time of day or shooting location does.

Well, you'd be wrong. Exposure is determined by three, and only three, parameters:

• Scene Luminance
• t-stop (usually closely approximated by the f-ratio)
• Shutter Speed

The flash power affects the scene luminance, and therefore affects the exposure.

Many things affect scene luminance, even down to the color of the subject. If I put up a shade or use a reflector, I change luminance. If I wait an hour for the sun to change position, I've affected scene luminance. Singling out flash makes no sense.

Who's "singling out flash"? As I said, scene luminance is one of the three elements of exposure, and the camera's flash will affect that particular element.

You did. I'll requote you from a couple posts up:

"The camera controls that affect exposure are the aperture, shutter speed, and flash power -- period"

To which I replied:

"I don't think flash power directly affects exposure anymore than the time of day or shooting location does."

Now you are saying you just meant scene luminance, which sounds like you are agreeing with what I originally said.

The flash power is just the amount of light in the scene, the exposure controls how much of it makes it to the image.

If we keep the aperture and shutter speed constant, then more flash power means a greater exposure, less flash power means a lower exposure.

As does shooting at night vs during the day. Is the Sun part of the exposure settings? Is time of day or the weather?

The scene luminance is one of three elements to exposure.

If you'd said that originally, I probably wouldn't be arguing with you now.

I feel like if you are going to call flash power part of the exposure than we should also call "how far I open my drapes in the living room during little Sally's b-day party" part of the exposure.

Well, best of luck to you, then.

If I open my drapes, does that not affect scene luminance?

Yes (well, assuming it's not dark outside). Did I say or imply otherwise?

Just above you said "best of luck to you" which I interpreted as a dismissal of my statement as incorrect.

 

[tomtom50]

Leonard Migliore wrote:

tomtom50 wrote:

Ahh, but isn't this the same as M + autoiso? Nope. Try using exposure compensation in M + autoiso! In Tv mode you can use exposure compensation, and it has all the goodness it has in other auto modes.

Perhaps a bit off topic, but that's a Canon disease. On Nikons, you can indeed use exposure compensation in manual with auto ISO and it works just like Pentax's Tv mode as you describe it.

 

[EinsteinsGhost]

gollywop wrote:

EinsteinsGhost wrote:

gollywop wrote:

EinsteinsGhost wrote:

Allan Olesen wrote:

tomtom50 wrote:

The core thing we are doing (adjusting camera settings to get the right brightness balancing other attributes) hasn't changed, so neither should the word.

You hit the nail on the head here. But probably not as you intended.

I think a lot of people are mislead to think that exposure means "the act of getting the desired brightness". And those people will reach the incorrect conclusion that you did.

But exposure never had that meaning. And consequently your logic fails.

Exposure simply means that a sensor or film is exposed to light. Anything else you relate to the process of getting the desired brightness is not exposure.

By the definition being promoted in these re-created threads, exposure doesn't really need a film or sensor, or any kind of sensitometry.

You continue to be in error. Check out, for example,

http://en.wikipedia.org/wiki/Exposure_(photography)

where it says

exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

The medium is always assumed; what is in question is which factors are in play (and which are not). That question is answered directly with the part that says exposure is defined as:

Hv = Ev .t

where

• Hv is the luminous exposure (usually in lux seconds)
• Ev is the image-plane illuminance (usually in lux)
• t is the exposure time (in seconds)

What is mentioned there are the factors that are in play.

1-Why do you think it mentions a photographic medium?

Because it explicitly mentions a photographic medium.

The question is: Why?

2-What do you think the exposure time relates to? And is it completely independent of the characteristics of photographic medium?

Gee, that's a tough one. When you change SS does your sensor change? When you change cameras to one with a different sensor, does the 1/100s SS change duration? I don't know; I really find it difficult to answer these questions. But perhaps you can, and then you can answer your own question.

The question was: What do you think the exposure time relates to?

--
gollywop

 

[bosjohn]

it was a variable back in the good old black and white film days as well. ISO was quite flexible and changes in your iso and development could alter the characteristics of you final negative. Changes such is increasing or decreasing contrast and grain and changing the curve of the exposure. For instance many photographer choose to expos tri-x on or even two stops under because it gives them better shadows

bosjohn aka John Shick [email protected]

 

[Gerry Winterbourne]

gollywop wrote:

Gerry wrote:

gollywop wrote:

You continue to be in error.

exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

The medium is always assumed; what is in question is which factors are in play (and which are not). That question is answered directly with the part that says exposure is defined as:

Hv = Ev .t

where

• Hv is the luminous exposure (usually in lux seconds)
• Ev is the image-plane illuminance (usually in lux)
• t is the exposure time (in seconds)

By any rf defining the meaning of a term in one context can alter - or wipe out ational use of English exposure time, as opposed to exposure duration, should mean not how long the exposure was but when it was taken. But, of course, this is pedantry gone mad. Everyone knows that exposure time can have different meanings depending on context. After all, that's true of a lot of expressions.

Indeed, it's true of exposure too. There's nothing wrong with the definition you quote here and it's fine in the context for which it is intended. But, like exposure time, exposure has other meanings depending on context. It isn't an error, as you suggest, to use a term in a different context from the one you happen to prefer.

The logic failure in my title refers to the idea of thinking that exposure can only have one meaning while defining it by reference to a term that can have multiple meanings - if all terms must have just one meaning the definition itself is wrong; or multiple meanings are fine.

Pedantry of the most errant kind.

The time is stated to be given in seconds. Such a criteria is completely meaningless relative to time of day since no origin is given, and even if one were, the resulting figure would have no immediate meaning to anyone.

You've completely missed the point, which is that "exposure time" has at least two meanings (1) time of occurrence - the general English meaning - and (2) duration of exposure - the special photographic meaning assigned in the definition you quote.

As you say, the unit of measurement renders one of these meanings irrelevant in the context. Indeed, it's the context that points to which meaning of the two is intended.

What you and the others trying to pin down "exposure" to only the meaning defined above is that, just like "exposure time" "exposure" has more than one meaning. Moreover, as with "exposure time", which meaning is intended is clear from the context.

No amount of definition of a term in one context can invalidate or alter its meaning in other contexts. A non-photography illustration: my profession before I retired was the design and construction of process plants. My role was to ensure the process vessels were strong enough, which entailed evaluating stresses - and "stress" had a very specific meaning, in everyday terms the intensity of applied force.

Controlling the processes was, of course, vital. When construction was complete but before setting it to work the systems engineers ran a series of stress test on the control systems. Their definition of stress was nothing like mine although we were both engineers (my illustration ignores other disciplines such as health and language, which also use stress to mean different things).

 

[bobn2]

tkbslc wrote:

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

tkbslc wrote:

Great Bustard wrote:

And here we are with a camera that has an ISOless sensor:

http://www.dpreview.com/forums/post/37235114

If we did the same with a camera that had a non-ISOless sensor, the pushed ISO 100 photo would be more noisy.

As "we" have been saying, the ISO setting is a matter of pre-processing the light that falls on the sensor, and, as such, is not an element in exposure, but an element in processing.

Thus, your challenge, and my answering that challenge, is irrelevant in terms of what exposure is and isn't.

If you had taken that shot with the same ISO and reduced shutter speed by 6 stops and then brightened it with RAW editing software, you'd have the same shot, too.

No, you'd have a rather different photo. You'd have a photo that was made with 64x (6 stops more) light. Big difference.

reducing the shutter speed decreases the light, but either way, I corrected for it with the RAW editor, just as those pushing the ISO do.

Apologies -- I misinterpreted "reduced shutter speed" and was thinking the exact opposite. In any case, the photos in the link above were shot with the same camera and exposure, thus the same amount of light and thus the same noise.

Your idea of reducing the shutter speed, and thus reducing the light, would make for a much more noisy photo.

In theory, anyway.

Practice supports the theory.

 

[tomtom50]

Josh152 wrote:

Great Bustard wrote:

gollywop wrote:

jrtrent wrote:

tomtom50 wrote:

Fir film cameras exposure is aperture and shutter speed, because those are the dials you twist picture optimally bright balancing what you need for other attributes like dof, sharpness, and blur. Adjusting your camera to get the right brightness balancing the other attributes needed a good strong word because that was an important part of taking good pictures.

Now with digital camera we have three settings to get the right brightness balancing the other attributes. We know have new attributes in the mix, DR, detail, and noise

I like your thinking, but I don't really see much difference between digital and film with these three variables. ISO was still something that was chosen, and for those who used cut film or multiple camera bodies, there was some flexibility from shot to shot--though not as easily as can now be done with digital!

This blurb reflects my use of exposure and ISO:

Exposure determines how much light gets to the film. All still cameras have two fundamental controls for this: lens aperture and shutter speed. The combination of the two is the exposure value, or EV used for exposure. Film speed (discussed later) determines the quantity of light that will properly expose the film. The combination of film speed and the brightness of the scene determine an EV that can be translated into specific combinations of aperture and shutter speed to capture the proper quantity of light. http://johnlind.tripod.com/science/scienceexposure.html

Good usage is usage that successfully communicates the relevant information, and becomes widespread. Technology changes and the words meanings change as well. That's why we dial phone numbers on phones that have no dials.

Good point. And a concept of exposure that includes three variables instead of two makes good sense to a lot of picture takers, some of whom have become quite famous and even written books using this idea. The "exposure triangle" has helped several people I know to get the results they want a much higher percentage of the time.

Yes, but they could have been helped just as well with a "brightness triangle" and come away with a better and more accurate idea of what they were doing.

Thing is, "brightness triangle" doesn't sound cool like "exposure triangle". I mean, would you rather say you're the trash man or say you're a sanitary engineer? ;-)

I was thinking the same thing. At some point "exposure" became kind of a status word. People who self identify as Photographers like to talk about a photos "exposure" because it makes them sound and more importantly feel more technical and savvy than their non photographer friends who talk about how a photo is too bright or too dark.

Refusing to let a nice word like exposure evolve because one doesn't like the meaning of words changing, and instead minting new words with slightly different meanings happens, but not as often as schoolmarms would wish.

Language is democratic. The usage that is widely adopted in the one that wins.

That is why we still dial a phone number, instead of keying or tapping or whatever.

People are used to think of exposure as getting the right brightness, and aperture & shutter speed & ISO as the things you adjust to get their.

People trying to set their cameras could care less about equations developed that were applicable to film, or what Wikipedia says in 2013.

Imagine you are teaching photography. Not photograph's technology, photography.

1. You set exposure by adjusting f-stop, aperture, and ISO to get the right brightness. Each of these affects your picture differently, so we are going to learn how to get the right exposure and the best picture by best balancing these settings.

2. You set exposure by adjusting f-stop and aperture to adjust the amount of light hitting the sensor. Each of these affects your picture differently. Also you set the gain on the sensor so your file has the right brightness range. This affects your picture as well. We will learn how to aperture, shutter speed, and ISO adjustments affect your picture so you can choose the right exposure and amplification setting.

The latter delves into the technology more than is needed to take the best picture, and so is not a good word (as defined for film) to use with digital cameras. So we can expand the meaning of the word a bit or drop it entirely for reasons only techies understand?

 

[tomtom50]

yardcoyote wrote:

Exactly. I am a digital newbie and one of the things I am finding exciting, and very challenging, is the new role of ISO in the whole exposure dynamic. It was always there, but now that you can change it in every shot it is a new factor in decision making. That's what exposure always meant to me-- a set of decisions you make so that the correct amount of light falls on the picture plane to create the image you want.

The fact that a set of definitions originally used with film may need to be expanded to cover the needs of a new technology is hardly the end of the world. Nor is it the end of the world for an English word to have two definitions, even two technical definitions within the same field. You can have "exposure: film photography" and "exposure: digital photography" without harming the English language one bit. That's how English works. It's the original big tent.

If you want to blow your mind, consult the definition of the word "set" in an reputable unabridged dictionary. It's a noun, it's a verb, it has perhaps a dozen definitions in everyday use, plus technical terms in fields like mathematics, and nobody seems to get upset about it.

Yes! Thank you.

 

[hjulenissen]

tomtom50 wrote:

Language is democratic. The usage that is widely adopted in the one that wins.

That is why we still dial a phone number, instead of keying or tapping or whatever.

In that case Mandarin wins?

Loading…

listverse.com

I don't believe that language works as a homogenous majority vote. Rather, there are "islands" of people who use words and language in a certain way. Phycisists and engineers, for instance. And enthusiast photographers.

If 9/10 compact camera users talk about "exposure" in a certain way, this may or may not affect the system camera users who spends a lot of time learning their cameras.

-h