Why is aperture backwards??

[bleirer]

Well, to quibble a little bit: the ISO standard is related to final camera image output, regardless of specific image format. It does not specifically require JPG for measuring ISO. You just can’t use the camera’s raw output to measure ISO because raw is not an image format. Raw requires further processing to turn into an image.

But the point I was making was the standard actually does explicitly define the sensitivity of the camera and how it changes with ISO. Some folks definitely get that confused with the more specific concept of “sensitivity of the sensor” as you rightly pointed out. That may or may not change depending on one’s definition of sensor and sensitivity.

As long as you agree that one can not make their camera more sensitive to light by turning up the iso, I am happy.

 

[kimball]

As long as you agree that one can not make their camera more sensitive to light by turning up the iso, I am happy.

Well, you switched "sensor" with "camera" and now we're in gentle disagreement. ;-)

So the point of the digital camera ISO standard is to assign historically- and photographically-meaningful labels to the various sensitivity settings of a digital camera. So instead of "sensitivity setting 1" "sensitivity setting 2" "sensitivity setting 3", etc, which no film photographer picking up a digital camera for the first time would intuitively understand, we have "ISO 100" "ISO 200" ISO 400" which is instantly meaningful to the photographic community and maintains a very relevant connection with photographic history. This ISO standard even refers to the ISO setting on digital cameras as the "sensitivity setting" (3.13) and says things like "For historical reasons, the sensitivity setting of a DSC is often labelled the 'ISO'" and "In some cases the sensitivity setting is set by the user. In other cases it is set automatically by the DSC." (DSC = Digital Still Camera)

It is quite clear that digital cameras have user-adjustable sensitivity settings, and we call those the ISO setting.

Now, I agree that in the strictest sense of the term sensitivity, a sensor will always count only 1 electron for each 1 photon captured by a photosite. That's just physics. But there's a whole host of analog and digital processes in a digital camera that scale that 1 electron into a larger and larger digital number, changing proportionally with the camera's ISO setting. That is the practical "sensitivity" which the ISO standard defines.

 

[bleirer]

Well, you switched "sensor" with "camera" and now we're in gentle disagreement. ;-)

So the point of the digital camera ISO standard is to assign historically- and photographically-meaningful labels to the various sensitivity settings of a digital camera. So instead of "sensitivity setting 1" "sensitivity setting 2" "sensitivity setting 3", etc, which no film photographer picking up a digital camera for the first time would intuitively understand, we have "ISO 100" "ISO 200" ISO 400" which is instantly meaningful to the photographic community and maintains a very relevant connection with photographic history. This ISO standard even refers to the ISO setting on digital cameras as the "sensitivity setting" (3.13) and says things like "For historical reasons, the sensitivity setting of a DSC is often labelled the 'ISO'" and "In some cases the sensitivity setting is set by the user. In other cases it is set automatically by the DSC." (DSC = Digital Still Camera)

It is quite clear that digital cameras have user-adjustable sensitivity settings, and we call those the ISO setting.

Now, I agree that in the strictest sense of the term sensitivity, a sensor will always count only 1 electron for each 1 photon captured by a photosite. That's just physics. But there's a whole host of analog and digital processes in a digital camera that scale that 1 electron into a larger and larger digital number, changing proportionally with the camera's ISO setting. That is the practical "sensitivity" which the ISO standard defines.

Base ISO is the sensitivity the standard defines. Some cameras this would be 200, some 100, sone 64. Raising a camera setting above base is nothing more than gain, not increased sensitivity to light. Nice chatting with you, I'll unwatch this thread now since we are starting to rehash the same points.

 

[Paul in GA]

Back to the original question. If you think of f stops as fractions it makes sense. f/8 or 1/8 is larger than f/22/or 1/22.

 

[kimball]

Base ISO is the sensitivity the standard defines.

I'm looking at the standard right now. This is not correct. Sorry we couldn't pursue this further. Feel free to start another thread if you happen to catch this and wish to continue the discussion.

Sorry to derail the aperture thread y'all.