The misconception the exposure triangle teaches is that for a given scene lighting
f/8, 1/200, ISO 400
and
f/8, 1/100s, ISO 200
are the same exposure* when they are clearly not.
They will both output the same image lightness but the ISO 200 shot has only half the exposure* of the ISO 100 shot and so the ISO 200 shot will have more visible noise because of the lower SNR due to the smaller exposure*
* exposure - amount of light that struck the sensor per unit area while the shutter was open
A visual concept might be useful to primary school kids but I don't need a triangle or any other visual concept to understand that for a constant image lightness, not constant exposure*, there is an inverse relationship between any 2 of aperture, shutter speed and ISO.
The misconception the exposure triangle teaches is that for a given scene lighting
f/8, 1/200, ISO 400
and
f/8, 1/100s, ISO 200
are the same exposure* when they are clearly not.
They will both output the same image lightness but the ISO 200 shot has only half the exposure* of the ISO 100 shot and so the ISO 200 shot will have more visible noise because of the lower SNR due to the smaller exposure*
* exposure - amount of light that struck the sensor per unit area while the shutter was open
Where does it say that? All it teaches is that there are three components: shutter speed and aperture which regulate the amount of light hitting a sensor and ISO which regulates sensitivity to the light. By changing one you have to change the other(s) to achieve an image without blown highlights or shadows. Isn't auto-ISO based on this?
Q.E.D.
For starters, in its very name by naming it an exposure triangle.
There are also many people on the internet preaching that all 3 of aperture, shutter speed and ISO control exposure and incorrectly try to use the triangle to show how.
In manual mode that is total nonsense because I set exposure* first by setting the widest aperture (smallest f-number) that gives my DOF and the slowest shutter speed that meets my blur requirements without considering ISO at all.
The camera can set ISO wherever it likes as long as important highlights are not clipped. I set the final image lightness in post.
If at base ISO there is highlight clipping then obviously I have to compromise on either dof or blur depending on the circumstances and which is least important.
A visual concept might be useful to primary school kids but I don't need a triangle or any other visual concept to understand that for a constant image lightness, not constant exposure*, there is an inverse relationship between any 2 of aperture, shutter speed and ISO.
* exposure - amount of light that struck the sensor per unit area while the shutter was open
Setting image lightness in post essentially is the same as changing ISO in camera.
Whether you need it or not does not make it wrong.
If somebody on internet interprets it wrong does not make it wrong.
You said it yourself that there is relationship between aperture, shutter speed and ISO. That is what exposure triangle says.
BTW what word exposure means on the film boxes? I do not think it means amount of light. 😀
This is where we disagree.
Yes, for a constant image lightness, not constant exposure*, there is an inverse relationship between any 2 of aperture, shutter speed and ISO.
There are many people on the internet who have the misconception that for a constant exposure there is an inverse relationship between any 2 of aperture, shutter speed and ISO.
I have shown why that is a misconception in my earlier example with the two sets of camera settings for a given scene lighting.
Many people incorrectly use exposure* and image lightness interchangeably as if they mean the same thing when they actually do not mean the same thing as shown, again, in my earlier example with the two sets of camera settings for a given scene lighting.
These exposure triangle believers often go into a head spin when I tell them I can change the image lightness in camera without altering the exposure* at all.
* exposure - amount of light that struck the sensor per unit area while the shutter was open
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I'd add to that - the purpose of a pedagogic aid, such as the 'triangle' is to facilitate mental models which provide understanding of how the components of a system work together. The 'triangle' doesn't do that - it facilitates a mental model which provides misunderstandings.
thats correct Danno . adjusting ISO In A,S,P can change exposure.
No-one is disputing that, so what point are you trying to make?
In the PAS modes ISO sets the target exposure* to output the image lightness the camera is programmed to for that ISO setting.
I explained why especially in manual mode the ET is nonsense.
NB. I quoted my whole sentence in your quote of what I said and not just the part that suits your agenda 😃😎
* exposure - amount of light that struck the sensor per unit area while the shutter was open
Yes
Indeed, nor does either of those make it right.
Is that all that it says?
You mean where it says '36 exposures'? If so, that is indulgence of an equivocation fallacy. In that context 'exposure' is referring to an instance of the exposure of a frame of the film to light, not to a quantitative measure of the exposure of that frame to light. It's perhaps unfortunate that photographic parlance includes such an equivocation, but using it to argue that the quantitative meaning is other than it is, is simply deliberate obfuscation. Do you honestly believe that if someone says their photo is 'over-exposed' what they meant is that they used too many frames to capture it?
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Didn't you see a smile after this question?
Here is an article on B&H website. Could you please tell me what is wrong in it?
Yes, I saw the smile, it wasn't clear what you meant by it.
Which article on the B&H website are you referring to?
The three things that directly affect how much light energy reaches the sensor do not include ISO. ISO affects exposure only in how it influences the selected metering mode to set aperture and/or shutter speed.
The so-called "exposure triangle" over-simplifies the mechanism, and leads folk to conclude such things as increasing ISO increases noise, when what's really going on is that the increased ISO makes the metering mode set aperture/shutter speed such that less light is collected, the real reason there's increased noise in the image.
Don't know about you, but I'd rather understand the specific mechanisms and their implications, not some over-simplified analogy...
Or if we included the EC control we could have a quadrangle (i suppose it would be a square, since the 'triangle' is always presented as equilateral). The 'threeness' of a relationship between three variables is not in question, what's in question is whether the 'exposure triangle' itself offers any additional insight into that relationship, apart from there being three variables.
I've taught a lot of computer science, and in that body of teaching there are a lot of posited analogies. Some work better than others, a lot of them just serve to confuse even further. And, the success in using any particular one really depends on the specific audience...
My suggestion is to discard all this "geometry" and just concentrate on understanding the mechanism itself...
