"Pros always use Manual exposure, A and S are for amateurs ..

Started 4 months ago | Discussions thread
Michael Fryd
Michael Fryd Veteran Member • Posts: 9,632
Re: "Pros always use Manual exposure, A and S are for amateurs ..

AwesomeIan wrote:


No it is not the same thinking as angels pushing planets around the sun. That is a completely unfair comparison. Just because the general consensus is that ISO is part of the exposure triangle doesn't make it untrue. You statements about ISO not being the sensitivity to light make me believe you may not have a good comprehension of this subject in the first place because that is exactly what increasing the ISO does. Boosting exposure in post is not like traveling in the future. It simply another method to adjust the ISO (or light sensitivity) in post. Nothing more. Nothing less.

Actually, while many think of the ISO setting as controlling the camera's sensitivity, that's not actually what it does.

Thinking of ISO as sensitivity is like thinking that angels push the planet around.  On a simplistic level it explains things, but when you look closely it is fundamentally wrong.

"Sensitivity" is the ability to "sense" something.  When it comes to digital cameras it refers to the ability to detect photons.   Down deep, what a sensor is really doing is counting photons.  The number of photons counted is the same whether the camera is set for ISO 100 or ISO 128,000.   If the photon wasn't seen by the sensor at ISO 100, it won't be seen at ISO 128,000.

What the ISO setting does do is alter how the collected data is processed.  At low ISO a particular photon count might map to a dark grey.  At a higher ISO that same photon count might map to bright white.  The sensitivity of the sensor is not altered.  No matter what the ISO it still counts the same number of photons.


Now you might think of the mapping from photon count to image brightness as being the "sensitivity" of the entire system.  This would include not only the sensor, in-camera, and post-camera processing, but the output device as well.

If the final printer is low on toner the printed image might look lighter.  If we are judging "sensitivity" by the result, then this lack of toner would reduce the "sensitivity" of the system.


Yes, it may sound like I am being ridiculous.  After all, why should anyone care what words are being used to describe the process?  As long as the student gets the right idea, why should the words matter?

The answer is that when you use the wrong words, the student frequently gets the wrong idea.  Like angels pushing the planets, the wrong idea can be useful in limited circumstances, however the correct idea is generally more helpful in the long run.

When you claim the adjusts the "sensitivity" of the camera, you give the impression that at higher ISO settings, the camera is able to capture lower levels of light.

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