It is exposure and it is a triangle

[steve_z]

Bill - You’re obviously an experienced photographer and I do respect your opinions, but your quiz is more about your post production LR skills than the camera’s settings. Sure, even 100 ASA film shot as if 800 can be corrected by altering the developing process. The fact that you can’t use the photo of your nice plant SOOC contradicts the point you’re trying to make, no?

Why does every handheld light meter have an ISO setting if ISO is not part of the exposure equation?

I don't see ISO as part of the "exposure equation", using your words, but as part of the "lightness equation".

The "lightness equation" being that there is a reciprocal relationship between any 2 of aperture, shutter speed and ISO in order to maintain a constant photo lightness for a given scene.

Hmmmm, I don't see it as part of the "Lightness Equation" but a part of the "Darkness Equation"!!!

ok, no problem but I stated what the "lightness equation" is.

What is the Darkness Equation you refer to?

 

[Ephemeris]

Cameras are engineered in accordance with an understanding of what exposure is and how it's determined; an understanding that has foundations in science going back to the 19th century. The following is taken from the "Manual of Photography," a technical examination of cameras and the photographic process first published in 1890 with multiple later editions having followed. This excerpt is from the 6th edition (1971):

"The exposure received by a film is governed by the strength of the light falling on it and by the time for which that light is allowed to fall. We have already seen that light falling on a surface is defined as illumination. The relation between exposure (E), illumination (I) and exposure time (t) is expressed by the equation E = I×t."

You'll note there's no mention of ISO, ASA or any other measure of the sensitivity of the medium to light in the description of exposure or among the factors directly determining exposure.

To link this understanding with contemporary digital photography, we can reference ISO 12232:2019, which defines ISO's role communicating an exposure index to the camera:

"An exposure index (EI) is a numerical value that is inversely proportional to the exposure provided to an image sensor to obtain an image. Images obtained from a DSC [digital still camera] using a range of EI values will normally provide a range of image quality levels. The photographic sensitivity of a DSC is a particular EI value calculated from the exposure provided at the focal plane of the DSC that produces a specified camera image signal level. The EI value for a specific image captured by a DSC shall be equal to the EI reference exposure of 10 lx⋅s divided by the focal plane exposure used to capture the image,..."

Again, we see an understanding of what exposure is and how it's determined that is consistent with the definition in use since the 19th century. Modern cameras are designed, engineered and built to function in accordance with this long and well-established understanding.

The answer to your question, "An exposure of what?" can, I think, be summarized as electromagnetic energy. In most cases, it's energy from the visible light portion of the spectrum. However, I suspect an imaging device engineered to be sensitive to areas of the spectrum in the IR, UV, or radio portions of the spectrum would define exposure similarly while using the relevant energy unit.

If you seek a more technical explanation or understanding, I would encourage you to search posts by bobn2 and Iliah Borg. To narrow the list of results, you might try associating the name with ISO12232:2019 or some other topical terms.

I came across this from SharkMelley who I think is a member here. He also links Bills noise graphs

We can see the noise figure of the analogue system increase as ISO /EI is changed. I'm not sure how the DSP is suppressed, perhaps you may know or Bill of course.

But what this says is as we move from detector we have some systems which we can or camera can control which alters the noise figure. The digital part likely to add some extras that we don't want.

Loading…

www.photonstophotos.net

We can see from Bill and his Nikon files here that the noise energy increases. I don't know how to convert the ADC bit readout (y axis) into something like dBm, but it will relate to a voltage and thus possible to calculate.

 

[FingerPainter]

Under Exposed <——- Correctly Exposed ——> Over Exposed

Yes, folks, there is a thing called “correct exposure” despite mangled attempts to explain that it doesn’t exist. Hint: you can find it sandwiched between under exposed and over exposed.

How does one achieve this mythical correct exposure? You have to turn any or all of these three dials:

Aperture dial

Shutter speed dial

These two adjust exposure

ISO dial (or use the ASA number printed on the roll of film).

This one is used to manage the lightness of the processed JPEG.

Alternatively, you can leave those dials alone and tinker with the relationship between your subject and the light source.

Lend a hand, if you would, please: which of the following three photos would you say is under exposed, correctly exposed, or over exposed?

First I will just use a dictionary or an article which defines these terms.

Just like speed means something, but shutter speed is different.

So under exposed simply means too dark for instance.

We've been though this before. Most dictionaries actually and correctly say that underexposed means did not receive enough light. not too dark. I quoted a numbee of dictionary definitions at ouy from top repurable dictionaries.

(Actually, I think it was 'Overexposed' we were talking about that the time but the same applies.)

 

[jrtrent]

Lend a hand, if you would, please: which of the following three photos would you say is under exposed, correctly exposed, or over exposed?

I like Adobe's take on what is overexposed and underexposed. They said, "In photography, we refer to images that are darker than the actual scene as underexposed, while those that are brighter are considered overexposed."

Not having seen the original scene myself, all I can do is guess, but with the first three pictures, I'd say the first is slightly overexposed, the second perhaps a bit underexposed, and the third more overexposed than the first. I like the second one best.

How about these two?

These appear to be pictures two and three from above but post-processed to have the same image brightness as number one.

With your Fuji X-T20, have you tried this shot with DR200% or DR400%? I'm not sure how their DR modes work, but I've liked how Olympus's auto gradation feature helps preserve shadow and highlight detail. Nikon's Active D-Lighting and Panasonic's i.Dynamic seem to work similarly. I used to have a Fuji EXR model, but while its dynamic range compression worked great on highlights, it left shadows too dark for my tastes.

 

[Bob]

Getting back to the original Christmas tree chart, you say the ISO is not mentioned, but it is implied in “E”.

Using 35mm film to illustrate my point, an ASA 50 requires more “signal” than, say, an ASA 800 roll. Thus, the combination of shutter speed and aperture which equals “E” would be different for these two ASA/ISO choices.

So, yes, shutter and aperture are the only two camera settings which set the expsosure, but the ISO is the underlying starting point, a third variable so to speak.

 

[Bob A L]

Under Exposed <——- Correctly Exposed ——> Over Exposed

Yes, folks, there is a thing called “correct exposure” despite mangled attempts to explain that it doesn’t exist. Hint: you can find it sandwiched between under exposed and over exposed.

How does one achieve this mythical correct exposure? You have to turn any or all of these three dials:

Aperture dial

Shutter speed dial

ISO dial (or use the ASA number printed on the roll of film).

Alternatively, you can leave those dials alone and tinker with the relationship between your subject and the light source.

ABSOLUTELY RIGHT ON. Actually it's really a very simple thing that has been easy to understand for years and years.

But in today's world, it seems we need a 200 page instruction book in order to properly boil water.

 

[J A C S]

Sorry Bob&Bob, this is not right.

Under Exposed <——- Correctly Exposed ——> Over Exposed

Yes, folks, there is a thing called “correct exposure” despite mangled attempts to explain that it doesn’t exist. Hint: you can find it sandwiched between under exposed and over exposed.

Of course, you have to tell us now what under and over exposed are.

How does one achieve this mythical correct exposure? You have to turn any or all of these three dials:

Aperture dial

Shutter speed dial

ISO dial (or use the ASA number printed on the roll of film).

And how do I know that I got it right (assuming that I am in some auto mode anyway)? BTW, in Av mode, for example, turning the aperture dial does not change the exposure.

 

[steve_z]

Under Exposed <——- Correctly Exposed ——> Over Exposed

Yes, folks, there is a thing called “correct exposure” despite mangled attempts to explain that it doesn’t exist. Hint: you can find it sandwiched between under exposed and over exposed.

Actually that is exactly where my correct exposure is located.

Firstly, for me "correct exposure" is when the aperture, shutter speed and ISO settings allow the maximum amount of light to strike the sensor during a shutter activation that meet my dof and blur requirements without clipping highlights I want to keep.

So if more light hit the sensor than the maximum as described above then the image is over exposed.

if less light hit the sensor than the maximum as described above then the image is under exposed.

So my correct exposure will always be located between what I see as under or over exposed.

How does one achieve this mythical correct exposure? You have to turn any or all of these three dials:

Aperture dial

Shutter speed dial

ISO dial (or use the ASA number printed on the roll of film).

That goes without saying and no-one is disputing that.

Alternatively, you can leave those dials alone and tinker with the relationship between your subject and the light source.

yes, and that is because the 3 things that affect exposure (as described above) are:

• scene luminance
• aperture
• shutter speed

 

[Bill Ferris]

Getting back to the original Christmas tree chart, you say the ISO is not mentioned, but it is implied in “E”.

No, it isn't. Per the top post, the red E represents the amount of light hitting the whole sensor or some specific part of the sensor. Regardless of the ASA film used or the selected digital ISO, the amount of light projected upon the light-sensitive medium is strictly determined by scene brightness, lens aperture and exposure time.

Using 35mm film to illustrate my point, an ASA 50 requires more “signal” than, say, an ASA 800 roll. Thus, the combination of shutter speed and aperture which equals “E” would be different for these two ASA/ISO choices.

So, yes, shutter and aperture are the only two camera settings which set the expsosure, but the ISO is the underlying starting point, a third variable so to speak.

ISO isn't the underlying starting point. In fact, that notion is among the fundamental problems with the so-called exposure triangle. It teaches photographers to make a secondary camera setting (ASA or ISO) the #1 priority.

Whether you shoot film or digital, the primary camera settings are f-stop and shutter speed. Respectively, they control depth of field and how movement will be rendered. Both are important creative elements. Taken together, they're the two settings that, along with scene brightness, determine exposure.

The ASA or ISO should be chosen to pair well with the selected exposure. A compatible ASA film will result in a negative having the desired tonality. A compatible ISO will result in a JPEG having a pleasing lightness. If that ISO falls within the camera's invariant range, image lightness can be adjusted by multiple stops without any loss of image quality.

Even if the photographer is limited to having only one ASA film stock or just one digital ISO available, exposure is still determined by scene brightness, lens aperture, and exposure time.

Neither ISO nor ASA is represented in the OP's chart.

 

[steve_z]

So, yes, shutter and aperture are the only two camera settings which set the expsosure,

yes totally agree

but the ISO is the underlying starting point,

Here I disagree because it doesn't have to be a starting point. For me it is much better to set ISO last after aperture and shutter speed,

When I set the exposure, aperture and shutter, the ISO setting the camera will set afterwards (Auto ISO) is totally irrelevant to me as long as highlights I want to keep are not clipped. I set the final photo lightness in post, not in the camera.

a third variable so to speak.

 

[J A C S]

ISO isn't the underlying starting point. In fact, that notion is among the fundamental problems with the so-called exposure triangle. It teaches photographers to make a secondary camera setting (ASA or ISO) the #1 priority.

Does it, really?

Whether you shoot film or digital, the primary camera settings are f-stop and shutter speed. Respectively, they control depth of field and how movement will be rendered. Both are important creative elements. Taken together, they're the two settings that, along with scene brightness, determine exposure.

The ASA or ISO should be chosen to pair well with the selected exposure. A compatible ASA film will result in a negative having the desired tonality. A compatible ISO will result in a JPEG having a pleasing lightness. If that ISO falls within the camera's invariant range, image lightness can be adjusted by multiple stops without any loss of image quality.

Of course, a poorly chosen ISO can blow the whole image, or burry it in lower region of the RAW, where the noise would be higher.

 

[steve_z]

ISO isn't the underlying starting point. In fact, that notion is among the fundamental problems with the so-called exposure triangle. It teaches photographers to make a secondary camera setting (ASA or ISO) the #1 priority.

Does it, really?

Yep, that's the message the overwhelming majority of presenters in youtube videos taught me before I realised the fallacies the expoure triangle is based on and consequently abandoned it.

Even Bob a couple of posts back posted his opinion that ISO is the underlying starting point. I disagreed and posted why.

Whether you shoot film or digital, the primary camera settings are f-stop and shutter speed. Respectively, they control depth of field and how movement will be rendered. Both are important creative elements. Taken together, they're the two settings that, along with scene brightness, determine exposure.

The ASA or ISO should be chosen to pair well with the selected exposure. A compatible ASA film will result in a negative having the desired tonality. A compatible ISO will result in a JPEG having a pleasing lightness. If that ISO falls within the camera's invariant range, image lightness can be adjusted by multiple stops without any loss of image quality.

Of course, a poorly chosen ISO can blow the whole image, or burry it in lower region of the RAW, where the noise would be higher.

And that is exactly why ISO is totally irrelevant to me as described in earlier posts.

 

[Ephemeris]

Under Exposed <——- Correctly Exposed ——> Over Exposed

Yes, folks, there is a thing called “correct exposure” despite mangled attempts to explain that it doesn’t exist. Hint: you can find it sandwiched between under exposed and over exposed.

How does one achieve this mythical correct exposure? You have to turn any or all of these three dials:

Aperture dial

Shutter speed dial

ISO dial (or use the ASA number printed on the roll of film).

Alternatively, you can leave those dials alone and tinker with the relationship between your subject and the light source.

ABSOLUTELY RIGHT ON. Actually it's really a very simple thing that has been easy to understand for years and years.

But in today's world, it seems we need a 200 page instruction book in order to properly boil water.

I think maybe a health and safety course if booking water in a kettle as well.

I don't think the nice ISO folks define correct exposure. A method for measuring iso based on noise and based separately on signal saturation.

My exposure is better than your exposure, or at least that what's the camera salesperson told me 2024. Better exposure year.

 

[chrisfisheye]

ISO isn't the underlying starting point. In fact, that notion is among the fundamental problems with the so-called exposure triangle. It teaches photographers to make a secondary camera setting (ASA or ISO) the #1 priority.

Does it, really?

Yep, that's the message the overwhelming majority of presenters in youtube videos taught me before I realised the fallacies the expoure triangle

Before you misinterpreted the exposure triangle

 

[steve_z]

ISO isn't the underlying starting point. In fact, that notion is among the fundamental problems with the so-called exposure triangle. It teaches photographers to make a secondary camera setting (ASA or ISO) the #1 priority.

Does it, really?

Yep, that's the message the overwhelming majority of presenters in youtube videos taught me before I realised the fallacies the expoure triangle

Before you misinterpreted the exposure triangle

And yet you do not have the ability to post how I personally have misinterpreted it.

I haven't misinterpreted what presenters in videos "taught" in them. There are plenty of presenters in youtube videos attempting to "teach" the exposure triangle falsely claiming that to maintain a constant exposure when you change one of aperture, shutter speed and ISO you need to change one of the other 2 by the inverse amount.

I have posted numerous times how that is just plainly not true in all cases.

Which sentences in what I said below are you claiming are not true?

"Firstly, for the sake of clarity, when I say "exposure" I mean the amount of light striking the sensor per unit area during a shutter activation.

So, in aperture priority and for a given scene, if you raise ISO by 1 stop you are instructing the camera to actually halve the exposure (not keep it constant) by setting a 1 stop faster shutter speed in order to maintain the same photo lightness."

 

[A74Me]

Bill - You’re obviously an experienced photographer and I do respect your opinions, but your quiz is more about your post production LR skills than the camera’s settings. Sure, even 100 ASA film shot as if 800 can be corrected by altering the developing process. The fact that you can’t use the photo of your nice plant SOOC contradicts the point you’re trying to make, no?

Why does every handheld light meter have an ISO setting if ISO is not part of the exposure equation?

I don't see ISO as part of the "exposure equation", using your words, but as part of the "lightness equation".

The "lightness equation" being that there is a reciprocal relationship between any 2 of aperture, shutter speed and ISO in order to maintain a constant photo lightness for a given scene.

Hmmmm, I don't see it as part of the "Lightness Equation" but a part of the "Darkness Equation"!!! It can't be both simultaneously or we'd have ourselves a good old fashioned paradox!!! ;-)

See, your triangle would have way too many interpretations. Maybe that's why the founding father whom of course are not near as smart as we here are, called it the Exposure Triangle!

John

love it john. iso controls darkness

lets see that discussion play out on the forums.

 

[steve_z]

Bill - You’re obviously an experienced photographer and I do respect your opinions, but your quiz is more about your post production LR skills than the camera’s settings. Sure, even 100 ASA film shot as if 800 can be corrected by altering the developing process. The fact that you can’t use the photo of your nice plant SOOC contradicts the point you’re trying to make, no?

Why does every handheld light meter have an ISO setting if ISO is not part of the exposure equation?

I don't see ISO as part of the "exposure equation", using your words, but as part of the "lightness equation".

The "lightness equation" being that there is a reciprocal relationship between any 2 of aperture, shutter speed and ISO in order to maintain a constant photo lightness for a given scene.

Hmmmm, I don't see it as part of the "Lightness Equation" but a part of the "Darkness Equation"!!! It can't be both simultaneously

Yes it can if your Darkness equation is the same as the "Lightness Equation".

The issue with the exposure triangle is that for a given name there are incorrect teachings from many youtube presenters about the relationship between ISO, aperture and shutter speed.

or we'd have ourselves a good old fashioned paradox!!! ;-)

See, your triangle would have way too many interpretations. Maybe that's why the founding father whom of course are not near as smart as we here are, called it the Exposure Triangle!

John

love it john. iso controls darkness

lets see that discussion play out on the forums.

His comment was addressed in my reply earlier this thread to his post.

 

[JohnSil]

Bill - You’re obviously an experienced photographer and I do respect your opinions, but your quiz is more about your post production LR skills than the camera’s settings. Sure, even 100 ASA film shot as if 800 can be corrected by altering the developing process. The fact that you can’t use the photo of your nice plant SOOC contradicts the point you’re trying to make, no?

Why does every handheld light meter have an ISO setting if ISO is not part of the exposure equation?

I don't see ISO as part of the "exposure equation", using your words, but as part of the "lightness equation".

The "lightness equation" being that there is a reciprocal relationship between any 2 of aperture, shutter speed and ISO in order to maintain a constant photo lightness for a given scene.

Hmmmm, I don't see it as part of the "Lightness Equation" but a part of the "Darkness Equation"!!! It can't be both simultaneously or we'd have ourselves a good old fashioned paradox!!! ;-)

See, your triangle would have way too many interpretations. Maybe that's why the founding father whom of course are not near as smart as we here are, called it the Exposure Triangle!

John

love it john. iso controls darkness

lets see that discussion play out on the forums.

These discussions will never end.

If perfect exposure was anumber line, it would be zero and runs both ways. I'm not sure if it would be lighter/darker or overexposed/underexposed!

What we call it is pretty irrelivant as long as we all agree and use that name universally!!!

John

 

[steve_z]

And you have hit the issue smack on top of the head - I doubt there will ever be universal agreement and so these types of discussion will go on forever.

 

[Bob A L]

"Firstly, for the sake of clarity, when I say "exposure" I mean the amount of light striking the sensor per unit area during a shutter activation.

There lies the difference for you and I. When I say "exposure" I mean the amount of lightness as observed in my photo when observed through my eyes.

I don't know of any way to look at my sensor to see how well it was exposed, but don't worry about it anyway, as it is what I deem the proper exposure of my photo that I am concerned with.

The difference is that I look at my photo and determine if it is what I consider properly exposed, and I suppose you look at your sensor and determine if it is properly exposed.