Correct Exposure???

[flyguy]

It started long ago but came to a head the Friday before Halloween when I was tasked by my bride of many years to take pics of the decorations in the front yard with a REAL camera. Late afternoon was BRIGHT to say the least; many of the decorations were COLORFUL and contrasty! I have been shooting in Aperture Priority for a long time. Checking the shots later it was obvious many were a tad too bright (except of course the shots after dark which were a different challenge). It was like the lens should have had sunglasses on??? My assignment to myself was to attack the daunting task of full manual mode so that is what I set about on my days off this week. I would take my usual shot in Aperture Priority, noting its settings for shutter speed, then shift to manual mode. Almost immediately I noticed that the shutter speed that the D7100 chose when in A mode was not always the same when in M mode. HUH!!!??? If not the same, I reset it to be the same then took a series of 3 - 4 shots for comparison sake, those shots typically set to shorten exposure time, thus underexposing some? Shots that were 1/3 or 2/3 of a stop had colors not so washed out. That brings me back to the topic of this thread, is there really a "correct" exposure or is it my personal choice to make? Yes, I get it, a shot can get over or under exposed; then there is that "grey" area somewhere in between. I shoot a lot of 'scapes, scenes where there is a LOT of contrast; a lot a bright juxtaposed to a lot of deep shadows. I want to get the exposure as close to "correct" as shot and minimize post processing. I feel it is better to slightly underexpose and correct some in post than to lose something by overexposing? By the way I am not a fan of matrix metering at all; I have both my D7100 and D850 set for center weighted and the center opened up wider than the default setting. I use a single focus point for 'scape work which is mainly what I shoot. Have used a 3 stop ND filter as sunglasses for my lens at times. The brightness challenge really hit me a few years back when I spent two days along the South Rim of the Grand Canyon, two days of cloudless skies and tons of scene contrast; I had to seriously post process many of those shots because they looked overexposed. Grrrrrrrrrrrrrrrrrrrrrr.........................

 

[JANuser]

In a situation like that I would use highlight weighted metering, rather than centre weighted. A circular polarizer would also have been useful.

 

[nokk]

i tend to overexpose a little so i get more shadow detail without increasing noise by brightening up shadows while post processing. but it's a balancing act not to clip the whites tones.

check your metering mode, is it spot or matrix? if it's spot it's only taking a small portion of the photo into account when the light meter tells you everything is fine. so if you're pointed at a darker area and reads it as midtone grey then everything else will be brighter as well.

do you have a histogram option on your camera? a lot of mirrorless cameras have a live histogram, which i prefer to using the light meter. with the histogram you get the whole picture in terms of exposure, you can see when you're clipping your highlights or shadows. dslrs usually have a histogram option for photos when you review them. you can double check your exposures before you leave. there may also be a setting on your camera that tells you when highlights are clipped.

 

[MartyD]

This is the way I understand it and only my opinion. In the days of slide film there was very much a proper exposure. Modern digital cameras have significant latitude but it is important to not overexposed highlights or underexpose shadows, hence the importance of the histogram.

Camera light meters use reflective light to establish proper exposure expecting the average scene to be 18% light reflective. If the metered portion of the scene is brighter or darker than that, the image will be underexposed or over exposed. Get an 18% gray card if you want to check your metering. Modern cameras try to recognize scenes and compensate when metering. The 7100 I believe has a scenes option as well to help in those difficult situations.

I still have my incident light meter I used years ago. It measures the light falling on the subject or scene to give proper exposure. It does not rely on the reflective nature of the scene.

You don’t say if you use auto ISO, but the different exposure readings in aperture setting may be due to the camera recognizing the focal length of the lens and adjusting the shutter speed to be certain it is fast enough to avoid camera shake. I don’t remember if my D7100 had that feature or not.

Steve has an excellent video on spot metering here.

 

[Rassie]

It started long ago but came to a head the Friday before Halloween when I was tasked by my bride of many years to take pics of the decorations in the front yard with a REAL camera. Late afternoon was BRIGHT to say the least; many of the decorations were COLORFUL and contrasty! I have been shooting in Aperture Priority for a long time. Checking the shots later it was obvious many were a tad too bright (except of course the shots after dark which were a different challenge). It was like the lens should have had sunglasses on??? My assignment to myself was to attack the daunting task of full manual mode so that is what I set about on my days off this week. I would take my usual shot in Aperture Priority, noting its settings for shutter speed, then shift to manual mode. Almost immediately I noticed that the shutter speed that the D7100 chose when in A mode was not always the same when in M mode. HUH!!!??? If not the same, I reset it to be the same then took a series of 3 - 4 shots for comparison sake, those shots typically set to shorten exposure time, thus underexposing some? Shots that were 1/3 or 2/3 of a stop had colors not so washed out. That brings me back to the topic of this thread, is there really a "correct" exposure or is it my personal choice to make? Yes, I get it, a shot can get over or under exposed; then there is that "grey" area somewhere in between. I shoot a lot of 'scapes, scenes where there is a LOT of contrast; a lot a bright juxtaposed to a lot of deep shadows. I want to get the exposure as close to "correct" as shot and minimize post processing. I feel it is better to slightly underexpose and correct some in post than to lose something by overexposing? By the way I am not a fan of matrix metering at all; I have both my D7100 and D850 set for center weighted and the center opened up wider than the default setting. I use a single focus point for 'scape work which is mainly what I shoot. Have used a 3 stop ND filter as sunglasses for my lens at times. The brightness challenge really hit me a few years back when I spent two days along the South Rim of the Grand Canyon, two days of cloudless skies and tons of scene contrast; I had to seriously post process many of those shots because they looked overexposed. Grrrrrrrrrrrrrrrrrrrrrr.........................

So why not take a shot in any mode of your choice and then review in the rear lcd screen? Display the picture on the screen and then superimpose either the "blinkies" to look for blown highlights, or superimpose the histogram and look at that to see where exposure landed. If overexposed, dial in some negative exposure compensation and try again, or dial in positive compensation for underexposed images. I bet this is the way the majority of us do it in the field.

 

[bjanes]

So why not take a shot in any mode of your choice and then review in the rear lcd screen? Display the picture on the screen and then superimpose either the "blinkies" to look for blown highlights, or superimpose the histogram and look at that to see where exposure landed. If overexposed, dial in some negative exposure compensation and try again, or dial in positive compensation for underexposed images. I bet this is the way the majority of us do it in the field.

+1

That's the way I evaluate exposure too.

The OP didn't state what type of decorations he was photographing. If they included lights, there could be a problem. At mid-day the lights would likely not even show up. At night the lights would dominate. It might be best to photograph at dusk when the brightness of the two elements would be more or less equal.

Bill

 

[gordon_g]

My suggestion would be to shot in full manual mode until you start to get comfortable getting exposure correct... you might not get some photos but I can guarantee you will learn a lot... as Rassie said use the blinkies and the histogram .. it won’t take long to start get a real solid understanding. When I started in went right to full manual and learned a lot... quickly... especially in the winter.

 

[gbodave]

In AP mode the camera selects the shutter speed for you. In manual mode you select the shutter speed so it's expected that the two shutter speeds will often be different (and better when in manual mode).

On exposure I strive for a balanced exposure which I define as an exposure that captures the brightest brights and the darkest darks whilst retaining detail in both. Doesn't always work out that way of course. There certainly isn't a "perfect" exposure but there could be an exposure that works "perfectly" in the conditions you faced and the look you wanted to achieve.

This whole topic is another subjective one (as is the case in a lot of photography related issues) so there will be a variation in practice. As examples, I've never found the need to look at a histogram. The exposure meter in the camera and my eyes have always been good enough. I've always used spot metering. It works fine for me. I've rarely used exposure compensation preferring to use F number, SS and ISO to achieve that balance I mentioned. I do use the blinkies which help to keep exposure slightly on the dark side.

 

[Squawk]

You suggest going into full manual but that’s not necessary. You can select manual and auto ISO. There are only 2 things that control exposure (aperture and speed) and on most cameras you have access to those on a thumb and finger so it’s really handy to have those under your control. ISO is like your exposure slider in your software – the more you bump it up the more degraded the image becomes so you fiddle with your exposure to bring it to an acceptable level giving weight to what’s important for the shot (DoF or speed). All this is visible in the view finder so you can be making the decisions on the fly in seconds. On exposure I use matrix, but in any scenario that’s high contrast it’s a problem as metering is based on mid tones, so there’s two solutions (both involve dialling in a bit of compensation). First guess if the average weight is towards the dark or bright side and dial in a bit to correction. Second is to look at the blinkies. I also use the histogram, but split it into RGB as I have a problem with just the reds getting blown (lots of red flowers out there). Lastly check what the dynamic range of your sensor is. If it’s say 10 EV and your composition involves say 12 EV you’re on a lost cause so in that case you’ll have to bracket and stack. Or you can do it the easy way….. https://bcgwebstore.com/product/secrets-to-exposure-and-metering-for-nikon/ don't delay, do it today!

 

[bjanes]

I also use the histogram, but split it into RGB as I have a problem with just the reds getting blown (lots of red flowers out there). Lastly check what the dynamic range of your sensor is. If it’s say 10 EV and your composition involves say 12 EV you’re on a lost cause so in that case you’ll have to bracket and stack. Or you can do it the easy way….. https://bcgwebstore.com/product/secrets-to-exposure-and-metering-for-nikon/ don't delay, do it today!

As Steve points out in his metering book you reference, the camera histogram does not represent the raw values but merely those of an embedded JPG preview and when the histogram shows clipping, there is usually some headroom in the raw file. To make the camera histogram more representative of the raw values you can set the Nikon picture control to neutral or flat, but he usually uses the Standard picture control to get a more snappy preview image. The camera histogram is also affected by the chosen profile, which with Nikon is either sRGB or AdobeRGB. Choose AdobeRGB to help prevent saturation clipping. ProPhotoRGB is not available.

For an example, I took a picture of a saturated red flower with the D800e, exposing with the red channel to the right. The picture control was standard and the color space was AdobeRGB. The camera histogram is shown.

You can only see EXIF info for this image if you are logged in.

Now let's look at the raw histogram as shown in the excellent raw evaluation software, Rawdigger. Note that the red channel is nearly 3 stops to left of clipping which occurs at about a 16 bit raw value of 16,000.

You can only see EXIF info for this image if you are logged in.

For better dynamic range and noise control, we could expose to that the red channel is exposed to to the right as shown below. The exposure is now 4 s at f/8, about 2.73 stops more. The camera histogram shows extensive clipping of the red channel (not shown).

You can only see EXIF info for this image if you are logged in.

The red channel on the camera histogram is very susceptible to clipping since the red white balance multiplier for the D800e is 1.97, resulting in the red channel values being multiplied by this amount for white balance. Since the red channel is actually less sensitive to red light, it is actually more resistant to clipping (a seeming paradox).

With modern sensors, exposure to the right is less critical than before, as Steve points out and may not be worthwhile. However, with a red flower it doesn't hurt to take a couple of bracketed exposures with more exposure.

Bill

 

[Squawk]

As Steve points out in his metering book you reference, the camera histogram does not represent the raw values but merely those of an embedded JPG preview and when the histogram shows clipping, there is usually some headroom in the raw file. To make the camera histogram more representative of the raw values you can set the Nikon picture control to neutral or flat, but he usually uses the Standard picture control to get a more snappy preview image. The camera histogram is also affected by the chosen profile, which with Nikon is either sRGB or AdobeRGB. Choose AdobeRGB to help prevent saturation clipping. ProPhotoRGB is not available.

For an example, I took a picture of a saturated red flower with the D800e, exposing with the red channel to the right. The picture control was standard and the color space was AdobeRGB. The camera histogram is shown.

View attachment 9473

Now let's look at the raw histogram as shown in the excellent raw evaluation software, Rawdigger. Note that the red channel is nearly 3 stops to left of clipping which occurs at about a 16 bit raw value of 16,000.

View attachment 9474

For better dynamic range and noise control, we could expose to that the red channel is exposed to to the right as shown below. The exposure is now 4 s at f/8, about 2.73 stops more. The camera histogram shows extensive clipping of the red channel (not shown).

View attachment 9475

The red channel on the camera histogram is very susceptible to clipping since the red white balance multiplier for the D800e is 1.97, resulting in the red channel values being multiplied by this amount for white balance. Since the red channel is actually less sensitive to red light, it is actually more resistant to clipping (a seeming paradox).

With modern sensors, exposure to the right is less critical than before, as Steve points out and may not be worthwhile. However, with a red flower it doesn't hurt to take a couple of bracketed exposures with more exposure.

Bill

Wow Bill, that's a proper response and your rawdigger is a great intro. Thanks. The reason I split my channels was I getting some awful red flower shots yet my general histogram was saying I was fine. This was on the D800. Armed with your post I'll dig a bit deeper Thanks again and all this from a little aside that I'd never expected to be noticed.

 

[Rassie]

As Steve points out in his metering book you reference, the camera histogram does not represent the raw values but merely those of an embedded JPG preview and when the histogram shows clipping, there is usually some headroom in the raw file. To make the camera histogram more representative of the raw values you can set the Nikon picture control to neutral or flat, but he usually uses the Standard picture control to get a more snappy preview image. The camera histogram is also affected by the chosen profile, which with Nikon is either sRGB or AdobeRGB. Choose AdobeRGB to help prevent saturation clipping. ProPhotoRGB is not available.

For an example, I took a picture of a saturated red flower with the D800e, exposing with the red channel to the right. The picture control was standard and the color space was AdobeRGB. The camera histogram is shown.

View attachment 9473

Now let's look at the raw histogram as shown in the excellent raw evaluation software, Rawdigger. Note that the red channel is nearly 3 stops to left of clipping which occurs at about a 16 bit raw value of 16,000.

View attachment 9474

For better dynamic range and noise control, we could expose to that the red channel is exposed to to the right as shown below. The exposure is now 4 s at f/8, about 2.73 stops more. The camera histogram shows extensive clipping of the red channel (not shown).

View attachment 9475

The red channel on the camera histogram is very susceptible to clipping since the red white balance multiplier for the D800e is 1.97, resulting in the red channel values being multiplied by this amount for white balance. Since the red channel is actually less sensitive to red light, it is actually more resistant to clipping (a seeming paradox).

With modern sensors, exposure to the right is less critical than before, as Steve points out and may not be worthwhile. However, with a red flower it doesn't hurt to take a couple of bracketed exposures with more exposure.

Bill

A very good reply. I found the cameras can easily clip the yellow colors as well. I tend to watch the yellows and reds since they will be the first to clip.

 

[gordon_g]

You suggest going into full manual but that’s not necessary. You can select manual and auto ISO. There are only 2 things that control exposure (aperture and speed) and on most cameras you have access to those on a thumb and finger so it’s really handy to have those under your control. ISO is like your exposure slider in your software – the more you bump it up the more degraded the image becomes so you fiddle with your exposure to bring it to an acceptable level giving weight to what’s important for the shot (DoF or speed). All this is visible in the view finder so you can be making the decisions on the fly in seconds. On exposure I use matrix, but in any scenario that’s high contrast it’s a problem as metering is based on mid tones, so there’s two solutions (both involve dialling in a bit of compensation). First guess if the average weight is towards the dark or bright side and dial in a bit to correction. Second is to look at the blinkies. I also use the histogram, but split it into RGB as I have a problem with just the reds getting blown (lots of red flowers out there). Lastly check what the dynamic range of your sensor is. If it’s say 10 EV and your composition involves say 12 EV you’re on a lost cause so in that case you’ll have to bracket and stack. Or you can do it the easy way….. https://bcgwebstore.com/product/secrets-to-exposure-and-metering-for-nikon/ don't delay, do it today!

This is technically inaccurate... Shutter speed, F stop, and ISO control Exposure... and I do agree it's not necessary but if someone is struggling with getting exposure correct than it's not bad to force yourself to manually set all three setting to learn how to get the exposures you want... as we all know there are no absolutes, there are many setting that will give a proper exposure. as long as you get the the finial result you are looking for neither one, nor the other is correct.. I was Merely making a suggestion how how to better understand exposure.

 

[Callie]

Having shot for years @ aperture priority and ISO 640 for most of it, I turned completely manual with AUTO ISO as per Steve's excellent book a few years ago. Must say, that has changed around the way I shoot . However, you must check the back because, sometimes, no matter what setting you choose, the ambient light will still not let you get what you think you should get. An do not forget the trusty EV dial, I use up to -3 EV in some instances. The thing to remember is shoot, look, adjust, repeat. Unfortunately, you cannot do that in the heat of the moment of a cheetah chase , so find some gulls and swallows and practice.

 

[Squawk]

This is technically inaccurate... Shutter speed, F stop, and ISO control Exposure... and I do agree it's not necessary but if someone is struggling with getting exposure correct than it's not bad to force yourself to manually set all three setting to learn how to get the exposures you want... as we all know there are no absolutes, there are many setting that will give a proper exposure. as long as you get the the finial result you are looking for neither one, nor the other is correct.. I was Merely making a suggestion how how to better understand exposure.


View attachment 9495

Oops, sorry Gordon. I was replying to the poster looking to go full manual rather than your excellent suggestion, just giving another idea in case they'd not figured it out. I also started with full manual as we selected iso in the shop (normally 100) and were stuck with that until the next roll of film. Your Bermuda triangle (where all the good shots nailed seem to dissappear) is spot on, but I think it's also useful to understand that it's only exposure and speed that are directly connected to exposure and iso is just to add gain when they run out (on the dark side, bright side calls for ND filters). No offence meant and totally agree that manual is the best way to fly.

 

[bjanes]

A very good reply. I found the cameras can easily clip the yellow colors as well. I tend to watch the yellows and reds since they will be the first to clip.

+1. An excellent point.

Yellow consists of the red and green channels. Some years ago I was photographing a yellow flower at our local botanical garden and noted that with metered exposure the camera histogram was blown out on the red channel and at clipping on the green channel. The metered exposure was 1/160 s at f/9. Decreasing exposure to 1/250 s at f/9 brought clipping under control. I didn't shoot images of the camera histogram, but FastRawViewer (another excellent program from the Rawdigger group) has the ability to show the raw histogram as well as the histogram of the embedded JPEG preview.

The first linked image shows the FastRawViewer screen with the raw histogram on the upper right. To display the raw histogram one clicks on the R icon circled in red on the lower left part of the screen. The red and green channels are just short of clipping. To show the embedded histogram, one clicks on the I icon and the second link shows image it. The green is at clipping and the red is severely clipped. Please ignore the buy photo icon--I am not trying to sell these images.

FastRawViewer is also an excellent utility to preview and cull your images, similar to PhotoMechanic but much more reasonably priced.

Bill

 

[Flyboy]

We do tend to make this magical pastime harder than it needs to be. I started using Manual, because that's all we had in the '50s.
Then I got my first light meter. I much preferred incident over reflected meters. , but there was always that niggling little concern...did I expose this right? THEN I got my first camera with Matrix metering! Talk about making a Dinosaur Dance and Sing! The fact is, Film can cover a sensitivity range of ~20-25 stops, while digital cameras cameras can only "see" about 11 stops, which is something we really don't have to think about, because the camera algorithms take care of most of that for us. Yay!
I, too have a D7100, which to me is a marvelous machine and handles most situations exceptionally well! Good results generally, and a little knowledge about exposure and metering, mine mostly from experience, but assisted by reading Bryan Peterson's "UNDERSTANDING EXPOSURE" made (for me at least) a noticeable difference and led to more and better keepers. Keep at it! The more we shoot the better we get!

 

[bjanes]

The fact is, Film can cover a sensitivity range of ~20-25 stops, while digital cameras cameras can only "see" about 11 stops, which is something we really don't have to think about, because the camera algorithms take care of most of that for us. Yay!

While negative films have a great dynamic range, shooting slide film such as Kodachrome or Fuji Velvia forces you go learn exposure and white balance rather quickly as they have limited DR. I haven't shot film for years, but back then I used slide film for most of my color work and the experience gained there was very helpful.

Bill

 

[gbodave]

I've found that blowouts on flowers can be from several different colours and the thing that is usually responsible is when the petals are waxy which have a degree of shine even if the light isn't too bright and that makes it much harder to keep luminance and vibrance under control.

 

[gordon_g]

Oops, sorry Gordon. I was replying to the poster looking to go full manual rather than your excellent suggestion, just giving another idea in case they'd not figured it out. I also started with full manual as we selected iso in the shop (normally 100) and were stuck with that until the next roll of film. Your Bermuda triangle (where all the good shots nailed seem to dissappear) is spot on, but I think it's also useful to understand that it's only exposure and speed that are directly connected to exposure and iso is just to add gain when they run out (on the dark side, bright side calls for ND filters). No offence meant and totally agree that manual is the best way to fly.

No Worries Peter... Just clarifying on the Exposure didn't want someone reading that going wait what... LOL. I totally get what your are saying as well though... and there is ALWAYS another way to do things I think that is what makes this such an interesting hobby to be honest. Anyway sorry if I came across as confrentational it was not meant to be Sir!

 

[bjanes]

This is technically inaccurate... Shutter speed, F stop, and ISO control Exposure... and I do agree it's not necessary but if someone is struggling with getting exposure correct than it's not bad to force yourself to manually set all three setting to learn how to get the exposures you want... as we all know there are no absolutes, there are many setting that will give a proper exposure. as long as you get the the finial result you are looking for neither one, nor the other is correct.. I was Merely making a suggestion how how to better understand exposure.


View attachment 9495

Technically speaking, ISO is not a part of exposure. With a given shutter speed, aperture, and scene illumination exposure is measured in lux seconds and is not affected by ISO. ISO does affect brightness of the rendered image if the other parameters are constant, but in some cases with an ISO invariant sensor it is advantageous to use a lower ISO while maintaining the same shutter speed and aperture, and then brighten the image in post.

See Jim Kasson's suggestions on exposing with the Nikon D850.

Bill

 

[Ralph]

This is technically inaccurate... Shutter speed, F stop, and ISO control Exposure... and I do agree it's not necessary but if someone is struggling with getting exposure correct than it's not bad to force yourself to manually set all three setting to learn how to get the exposures you want... as we all know there are no absolutes, there are many setting that will give a proper exposure. as long as you get the the finial result you are looking for neither one, nor the other is correct.. I was Merely making a suggestion how how to better understand exposure.


View attachment 9495

Totally agree with Gordon. While autoexposure is a great feature especially for those that dealt with film for most of their life, setting all three parameters manually will give the inexperience some insight into how all three interact. If you have the auto iso engaged you will basically get the same result result no matter what the shutter-speed or aperture settings are . But going manual on iso will give the inexperienced a better feel for the interplay between shutter speed, aperture settings and iso. I realize their is a fourth factor to consider, exposure compensation, but you must first grasp the concept of the other three.

 

[Not A Speck Of Cereal]

I would have shot Aperture mode and reviewed the histogram. I have my Picture Control settings set to FLAT (I do not shoot JPG in that mode) so trust the histogram, more or less. Then add a bit of experience from years of shoots (you just earned some with this shoot). With those considerations, you could continue to shoot in A mode, but dial in a bit of exposure compensation and keep shooting, with an occasional glance at the histogram to be sure you're on the right track.

I like the idea of highlight weighted metering (mentioned by JANuser above) and will try (once again) to get some experience with that. (So many options, so many cool things found in the owners manual that I've not put to good practice.)

Chris

 

[Rassie]

I tried highlight weighted metering a few times. It works great for medium to low contrast scenes. In high contrast scenes, in order to preserve the highlights it suppresses exposure to the point where the dark areas, and indeed the entire picture, are underexposed. So highlight weighted metering is not suitable for all conditions.

 

[kimball]

Technically speaking, ISO is not a part of exposure. With a given shutter speed, aperture, and scene illumination exposure is measured in lux seconds and is not affected by ISO. ISO does affect brightness of the rendered image if the other parameters are constant, but in some cases with an ISO invariant sensor it is advantageous to use a lower ISO while maintaining the same shutter speed and aperture, and then brighten the image in post.

See Jim Kasson's suggestions on exposing with the Nikon D850.

100% agreed.

Ansel Adams published his Photography Series of educational books--The Camera, The Negative, The Print--in the late 1940s. In the Negative, he begins Chapter 3, Exposure, with its definition (which was already established well before him):

The term exposure requires a definition. As our discussion of apertures and shutter speeds indicated, we can give equivalent total exposure to the film using relatively high intensity of light for a short time, or less intense light for a longer duration. States as a formula, this relationship can be expressed:

Exposure = Intensity X Time

Thus the same total exposure will occur if we increase the intensity of light reaching the film while reducing the exposure time proportionally.

[...]

We use the term "exposure" to refer to the camera aperture and shutter speed used to record a given subject.

And yet, unfortunately languages change over time. Definitions are descriptive of current common usage, not prescriptive of correct usage. Sadly the term "exposure" now has multiple meanings in photography and one has to understand the context of the conversation to determine which meaning is being used. Personally I can't stand this, but I finally admit that no matter how hard I slam the barn door, the horse has clearly already bolted.

In the modern context of discussing image lightness (whether an image looks "overexposed" or "underexposed" based on its subject's tones), ISO is now considered a variable in exposure by most photographers. Hence the inclusion of ISO in the exposure triangle. Personally I really wish it was called the "image lightness triangle," but I admit that doesn't easily roll of the tongue.

In the modern context of discussing image quality and noise, "exposure" is used in its original meaning--as the amount of light the sensor is exposed to. That is, as in the film days, only determined but shutter speed and aperture (for a given scene brightness). In this context ISO is a process that happens in camera electronics and/or camera software after the sensor exposure and after the shutter has already closed. In this context it makes no sense to think of ISO as a part of exposure, even though ISO does play a (limited) role in image quality.

Going forward, the key for folks coming across and using the term "exposure" is to recognize which meaning is being used, however much it might grate on us. :(

Edit: I'll also leave this here:

The Unbearable Lightness of Mystic "Exposure" Triangle

We should begin by saying that the point of all of this is not just to criticize one of the most repeated photographic myths out there – that's just a tool, because an incorrect understanding of the way that exposure and ISO work, as well as their roles during the shooting process, leads to a...

www.fastrawviewer.com