EXPLAINING THE MAGIC

[FingerPainter]

Regarding the Exposure Triangle, it doesn't have to be so complicated.

Here is an easy overview that I feel explains it very simply: The Exposure Triangle

It explains it simply and incorrectly.

Here is a partial list of errors:

"The Exposure refers to the amount of light that hits the sensor. " Actually, it refers to the amount of light hitting the sensitive medium per unit area.

"Maybe it is easier to understand if You imagine You have a film in Your camera, as the sensor doesn’t work very differently when it comes to the exposure." It works quite differently. For instance film of a different ISO reacts differently to a given exposure. Change the ISO of your camera and the sensor will still report the same voltage for a given exposure (unless the capacitance switch threshold of a dual conversion gain sensor is passed).

"ISO Defines the sensitivity of the film/sensor. Increased ISO means brighter photographs, but introduces more prominent noise." Actually the ISO setting of a digital camera does not define the sensitivity of the sensor. The sensors's sensitivity remains unchanged regardless of ISO setting. (Again there can be a single exception for dual conversion gain sensors, but even with them the change is not proportional to ISO setting.) Also, increased ISO doesn't introduce any more noise. Increasing the ISO can increase the Signal to Noise Ration on some cameras.

"Exposure Triangle Cheat Sheet" Increasing ISO does not produce a greater exposure. It produces a brighter image. But since exposure is an amount of light per unit area falling on sensitive medium, ISO does not affect this at all.

"Three Main Components of Exposure
In photography, there are three factors influencing how bright or dark your photograph will be." Exposure is not the same as "how bright or dark your photograph will be". In fact there is a fourth factor affectifn image lightness: the scene luminance. All of the four factors, except the ISO setting, affect the exposure. Exposure and ISO setting affect image lightness.

"A camera set to ISO 200 is double as sensitive as at ISO 100, thus doubling the amount of light." In fact, a camera set to ISO 200, but with Aperture and shutter unchanged will capture the same amount of light, not twice as much light. In a autoexposure mode, increasing the ISO setting from 100 to 200 will typically cut the amount of light captured in half.

"... digital sensors use algorithms to enhance the sensitivity to light." Digital cameras may use algortihms to enhance the cameras output sensitivity to light. Digital sensors do not.

"You can underexpose a photograph often by more than 3 stops and are still able to increase the exposure in post-processing...". SInce exoposure is how much light fell on the sensor per unit area while the shutter was open, it is impossible to change exposure in post-processing.

 

[FingerPainter]

Why not just change the name of the triangle to "the brightness triangle" thus avoiding the fallacy that ISO is part of the exposure but retaining the simplicity and explanatory power?

Well, that would get rid of one problem. But the usual presentation of the triangle comes with other errors too, such as

• the ISO setting controls the sessitivity of the sensor
• increasing the ISO setting causes more noise

 

[Forgottenbutnotgone]

Regarding the Exposure Triangle, it doesn't have to be so complicated.

Here is an easy overview that I feel explains it very simply: The Exposure Triangle

It explains it simply and incorrectly.

Here is a partial list of errors:

"The Exposure refers to the amount of light that hits the sensor. " Actually, it refers to the amount of light hitting the sensitive medium per unit area.

"Maybe it is easier to understand if You imagine You have a film in Your camera, as the sensor doesn’t work very differently when it comes to the exposure." It works quite differently. For instance film of a different ISO reacts differently to a given exposure. Change the ISO of your camera and the sensor will still report the same voltage for a given exposure (unless the capacitance switch threshold of a dual conversion gain sensor is passed).

"ISO Defines the sensitivity of the film/sensor. Increased ISO means brighter photographs, but introduces more prominent noise." Actually the ISO setting of a digital camera does not define the sensitivity of the sensor. The sensors's sensitivity remains unchanged regardless of ISO setting. (Again there can be a single exception for dual conversion gain sensors, but even with them the change is not proportional to ISO setting.) Also, increased ISO doesn't introduce any more noise. Increasing the ISO can increase the Signal to Noise Ration on some cameras.

"Exposure Triangle Cheat Sheet" Increasing ISO does not produce a greater exposure. It produces a brighter image. But since exposure is an amount of light per unit area falling on sensitive medium, ISO does not affect this at all.

"Three Main Components of Exposure
In photography, there are three factors influencing how bright or dark your photograph will be." Exposure is not the same as "how bright or dark your photograph will be". In fact there is a fourth factor affectifn image lightness: the scene luminance. All of the four factors, except the ISO setting, affect the exposure. Exposure and ISO setting affect image lightness.

"A camera set to ISO 200 is double as sensitive as at ISO 100, thus doubling the amount of light." In fact, a camera set to ISO 200, but with Aperture and shutter unchanged will capture the same amount of light, not twice as much light. In a autoexposure mode, increasing the ISO setting from 100 to 200 will typically cut the amount of light captured in half.

"... digital sensors use algorithms to enhance the sensitivity to light." Digital cameras may use algortihms to enhance the cameras output sensitivity to light. Digital sensors do not.

"You can underexpose a photograph often by more than 3 stops and are still able to increase the exposure in post-processing...". SInce exoposure is how much light fell on the sensor per unit area while the shutter was open, it is impossible to change exposure in post-processing.

Your points and corrections handily explain the failure of the "exposure triangle", as typically taught, to properly lay a foundation that maintains consistency as a new photographer gains experience and knowledge.

It need not be any more confusing for one new to photography to have the terms explained to him correctly from the onset, especially if he is using a smaller sensored camera, since there is often less tolerance for the substitution of amplification for adequate exposure.

It troubles me to see supposedly experienced and knowledgeable people arguing against adopting more accurate terminology, simply because they didn't think of it first. There is just no other reason to advocate teaching someone, new or otherwise, flawed theory to supposedly keep from confusing them. The truth is it is ultimately more confusing to have to unlearn something that isn't correct than to have it explained accurately in the first place.

I think back to the traumatic day when I found out there was really no Santa Claus...

Robert