The Exposure Triangle Is Misleading And Unnecessary.

When I first started out in digital photography I was initially lead astray by all the misinformation on the www and elsewhere the Exposure Triangle (ET) supposedly teaches.

The ET taught me that to maintain a constant exposure after changing one of aperture, shutter speed or ISO I needed to adjust one of the other two parameters by the reciprocal amount.

For example, the ET taught that for a given scene and lighting:

A. f/8, 1/400s, ISO 200

and

B. f/8, 1/200s, ISO 100

were the same exposure because both settings output the same image lightness.

After finally realising and accepting, by listening to people who actually knew what they were talking about, that exposure is the amount of light striking the sensor per unit area while the shutter is open I saw that the ET and its teachings is totally inconsistent with the established technical definition of exposure*.

Although both settings A and B will output the same image lightness, setting A will have had only half the exposure* of setting B and so the image from setting A will have more visible noise in the shadows because of the lower Signal to Noise Ratio due to the smaller exposure*.

At best, with the ET you could say that for a constant image lightness, not exposure*, there is an inverse relationship between any two of aperture, shutter speed and ISO. You shouldn't need a triangle or any other shape to understand that simple and basic concept, so the ET is unnecessary.

* exposure - amount of light striking the sensor per unit area while the shutter is open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

i have a great idea. Get Bob to delete the iso setting in the exif data of every image posted on this site. lets see how that goes down with the members. 😎

That would be a stupid thing to do. Why would anyone, except for you of course since you suggested it, want to do that? It makes no sense to do that.

Which sentences in my post do you think are not accurate?

this is a really low light image what do you think.

shutter speed 1/125 sec f2.8

How does what I think of that image have anything to do with my op?

Which sentences in my op do you think are not accurate?

well you recon ISO doesn't have anything to with exposure triangle ,so cant you figure out by looking at just shutter speed and aperture how much ambient light was reflected onto the subject in the image ? you have at least 5 others to back you up 🙄

You are again falsifying what I said just like you did in another thread. This is becoming a trend for you when you let your frustrations get the better of you and so you are now establishing a history of falsifying other members' posts.

In which sentence in my op do you claim I said "ISO doesn't have anything to (do) with exposure triangle"?

Which sentences in my op do you think are not accurate?

didnt you know that light meters only tell you what shutter speed and aperture to set on your camera to, 😉 they have no iso or asa setting on them at all.

None of that shows what I posted in my op is not accurate.

Which sentences in my op do you think are not accurate?

The Exposure Triangle Is Misleading And Unnecessary.

That is the thread title so we'll just have to disagree on that until I see something that proves what I posted is not accurate.

Any sentences in my op you think are not accurate?

Intensive noise reduction and artifacts on the image tell that it is underexposed.

ET is confusing also because they say "ISO speed affects image noise".

Danno,

I concur. I actually screenshot your DPR signature a few weeks ago when I thought the site was going down because it was clear, simple and correct.

I've received "exposure triangle" handouts from photographers whom I know comprehend why it's wrong, but they claim it helps people to understand. Best I can get from them is an agreement to disagree, and I scratch out "exposure triangle" and replace it with "image lightness triangle" on my own copy.

If people don't agree on definitions (and this thread provides a good example), the rest of the discussion can't move forward.

Sherm

Yep, that was another misconception I had from the ET until I saw the light (pun intended 😉 ) from you, bobn2 and a few others and became aware that it is a low Signal to Noise Ratio resulting from a small exposure* that makes noise visible.

* exposure - amount of light striking the sensor per unit area while the shutter is open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights.

You can see it from two angles:

1. A sensor has exactly one ISO value. The same as with film. As such, the exposure triangle makes no sense as you can‘t choose another film with a different sensitivity as you could with analog cameras.

2. Still, as digital cameras offer a virtual ISO setting to make setting of aperture and shutter speed easier in low light situations, you can use it instead of deliberate under-exposure setting. That this reduces S/N shouldn‘t be a big point as the same happened with high ISO films.

ISO is still convenient as it replicates the usage of different films. Older photographers still are used to the term and the implications from analog times and younger ones learned that a higher ISO setting is used in low light situations as if the sensor is more sensitive but more noisy as well. And we all learned that the highest ISO setting which still gives a reasonable S/N ratio is a measure for the low noise performance of the respective sensor.

Before someone else mentions it, yes, I made a simplification of not considering variable conversion gain between the sensor and the ADC. It doesn‘t change the sensitivity of the sensor, it only influences the overall noise. And I didn‘t consider pixel binning. Even though pixel binning is the closest to ISO of analog film. Larger pixels collecting more light/pixel. But this is not typically used when setting high ISOs.

I think that common usage of "well-exposed" by many people often means that the image lightness is acceptable and has nothing to do with lack of motion blur, etc.

This ambiguity in the common use of the terms exposure, well-exposed, under-exposed, etc. is at the heart of the problem. Is exposure being used to mean the lightness of the final image or to mean the combination of shutter speed and aperture, or yet again, to mean the total amount of light gathered per unit area, etc?

My personal preference is to try to point out this ambiguity and explain the different meanings, rather than simply condemn the use of the exposure triangle.