The Exposure Triangle Is Misleading And Unnecessary.

David,
Forget about the sensor. What matters are the camera and the photograph.

The effect of the ISO setting with JPEG images is much stronger than with RAW. Some cameras are “ISO Invariant.” As I understand, this means that you can shoot the same exposure at multiple ISO settings from 100 to 56,000, and the RAW image will be the same, and you can adjust brightness any of those photos with your RAW editor and get the same result.

My Canons are not like that. I tested them. The ISO setting definitely affects the RAW files. Is that because of the way the sensor works, or because of firmware inside the camera? Guess what? It doesn’t actually matter, does it? If I’m going to reduce my shutter speed and keep aperture constant, I need to increase the ISO setting. So that three-sided shape dynamic is there, no matter how much people dislike the expression :-)

It causes push ;)

Exposing 5 stops lower means capturing 5 stops less light.

By mistake ;)

I was doing a lot of photography in the 1970s, and I don't remember any mention of triangles.

Don

I have consulted my edition of Michael Langford's classic college text book "Basic Photography". He makes no mention of the term "exposure triangle". But in the section about light meters, he makes it quite clear that film speed, shutter speed and aperture are the 3 key parameters. That's the exposure triangle concept, if not "Exposure Triangle" TM. The exposure triangle name is just a catchy term for those 3 things to my mind, so it is as old as photography. What's newer, is the damn mysterious ISO knob on my cameras that seems to have replaced film speed as a parameter even though it isn't film speed. What it is, is exercising me now. Especially after spending the morning in bright sunshine pouring over maps for a shooting location only to have a monsoon pour down all afternoon leaving me twiddling my ISO dial....

Trying to rephrase the whole question in my head.

If (in a parallel universe) it were possible to varying the photoelectric effect, such that a photon hitting a photosite could kick out more than one electron, and we added a control to our cameras labelled "Sensitivity" that controlled this, would the exposure triangle then apply to digital cameras? For example, if we could set the control to produce 2 electrons, 3 electrons, 4 electrons etc for each photon.

To my simple mind, this sounds very much like having a variable sensitive sensor akin to swapping out Velvia 25 for Tri X (assuming it didn't collapse the false vacuum) :-)

EDIT: while waiting for a communications genius smart enough to come up with an explanation suitable for someone as stupid as me, I googled the phrase "exposure triangle". It's everywhere! Quote by just about any photographic resource you can find from B&H to Adobe. I honestly thought it was just a throw-away phrase. I can see how something so ubiquitous can do a lot of harm if it is wrong, and why responsible adults may be upset by its existence.

Mind you, one of the more hilarious objections I came across was a site where the author treated the exposure triangle as if it were geometry and tried to show it was incorrect by drawing actual triangles to reflect adjustments to the settings and complaining when said triangles failed and made no geometric sense. Correct or incorrect, it's a metaphor, you can't perform geometric transformations on a metaphor then complain it's mathematically incorrect!

I don’t honestly understand what are the correct and incorrect ways to think about my exposure settings while I shoot. Sincerely, how should I think?

Sometimes I nail it and sometimes I don’t. Most of the times when I get it wrong, it’s not the settings I’ve chosen but rather the nature of the light falling on my subject. Or I missed focus.

Years ago, I would drive to an island before dawn every Saturday, to photograph the SF Bay Bridge. Once I worked out the ideal spot and the ideal exposure settings… it all came down to light. Some days it rained. Some days there was fog. It went on like that for two months until I got the shot I wanted. It’s not just about thinking right and setting your camera right.

The viewer doesn’t care if the lighting was bad, or if it was hard, or if your foot hurt. They definitely don’t care about how you were thinking.

4, as it is light meters section, light is one of those.
And, key parameters to what?

Key things you can adjust on your camera to get different exposures.

This seems like another thread where the argument is over what is the definition of the word "exposure" in photography.

The definition of "exposure" is illuminance--time product.

Illuminance is controlled by two things - scene illumination and f-stop.
Time is time - shutter speed.

Therefore, by definition, digital ISO settings is not a factor in "exposure", at least directly.

Indirectly, setting your ISO adjusts the way the camera's meter chooses to set the exposure, if you are using an auto mode or the in-camera meter for a manual setting of exposure. The same is true of a hand-held light meter. So, indirectly, the setting of ISO can affect the exposure chosen, but that doesn't mean ISO is part of exposure. As shown above, it's not, by definition.

Too much to respond to all at once :-)

Langford doesn't use the phrase "exposure triangle" in his book, as I already mentioned. In the section Iliah referred to, in my edition I think Langford lists 8 different things to consider (including the illuminant). Elsewhere (I forgot to mark the page), somewhere about using a light meter he simplifies all this by stressing the importance of shutter speed, aperture and film speed (maybe because that is all you can set on most meters).

But to my mind, the concept of using those 3 parameters is basic introductory stuff, just to get you started. A fancy version of "Sunny 16". It doesn't stand up to intense scrutiny but it isn't meant to. It's just a starter metaphor. Perhaps the problem is that other people in internet world have run with it and blown it up beyond all reasonable application?

I don't think the idea was to provide a literal statement of photographic physics. If you are using film, you set a film speed, point your meter and the meter suggests combinations of shutter speed and aperture that will yield a well exposed image. You can use any of the combinations (until you hit reciprocity failure) and expect the same level of exposure. If you vary one of them and wish to retain the original level of exposure, you have to vary one of the other parameters. All three operate in lockstep. To me, it makes perfect sense as a quick and dirty rule of thumb metaphor for beginners.

The problems start with digital because the ISO knob isn't exactly the same as film speed. What the ISO knob does in practical terms as it isn't film speed is the adjustment I need to make to my out of date mental model.

Could you please provide a quote? I don't see "key parameter" occurring in my 7 and 9 editions.

Mine is the 1977 edition. I've lost the page but I agree he never said "key parameter" - that was my paraphrase.

EDIT: Ok, I found this: "On the face of it, measuring correct exposure might be thought to be (a) measuring total light reflected by the subject towards the camera (b) setting this reading against the manufacturer's film speed on the calculator dial, to find the required shutter setting at each aperture."

This is part of a longer section that considers more complicated things, but this is the essence of the exposure triangle idea, I think.

Because film processing is (supposed to be) fixed. Further, "well-exposed" means within latitude, and thus for the same negative film and processing one can vary exposure rather significantly and still get a "well-exposed" shot.

Processing isn't fixed with digital, especially when one shoots raw.

Interestingly, in some regards negative film is more forgiving than digital, partly because there is no forced clipping with the film.