Can we ETTR by increasing ISO?

Started Apr 8, 2012 | Discussions thread
Great Bustard
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In reply to apaflo, Apr 15, 2012

apaflo wrote:

Iliah Borg wrote:

It's ETTR.

ISO is not a part of exposure, so it is not ETTR. It is important to differentiate because for different cameras the results of applying ISO to get the histogram to the right are very different; and even for the same camera for different ISO settings results are still different, past certain ISO there is no benefit because read noise remains the same.

That is very poor use of language.

Consider that if we make a shot that is clipping white, we say it suffers from over exposure, while if we make a shot that is too dark we say it suffers from under exposure... and in either case that can be corrected by adjusting ISO!

ISO is not a part of exposure level , but it absolutely is a part of exposure control . The term "exposure" is commonly used to reference either term. For example:

"The ISO setting is one of three elements used to control exposure; "

And:

"So don't forget that along with f/stop and shutter speed, ISO is an important element of exposure control."

Those are from a Nikon web page on camera technology:

http://www.nikonusa.com/Learn-And-Explore/Nikon-Camera-Technology/ga5bvixe/1/ISO_Control.html

And we find such often cited sources as http://www.cambridgeincolour.com/tutorials/camera-exposure.htm

Where these statements are made:

"A photograph's exposure determines how light or dark an image
will appear when it's been captured by your camera. Believe it
or not, this is determined by just three camera settings:
aperture, ISO and shutter speed (the "exposure
triangle")."

"In photography, the exposure settings of aperture, shutter speed and ISO speed are [...]"

And you in particular must be well aware of how many RAW converters and image editors label software adjustments as "exposure" or "exposure compensation" when not a single on of them can possibly change the exposure level of the camera!

This is common usage, common terminology, and it is not wrong! And what necessarily has to be understood is that the "Exposure" in the term ETTR references "exposure control", not the level of photons hitting sensor.

Playing games with word usage is cute. It's not productive. Nor is it effective writing or effective instruction. Terms of Art are one thing, actual usage is another. And people who go to a dictionary to find a single definition that supports some particular meaning, while ignoring several other equally appropriate meanings as a method of arguing technical points are lacking in integrity.

The fact that the common usage of the term "exposure" is incorrect (just as people use the term "bokeh" to refer to the quantity of the blur as opposed to the quality of the blur) does not justify the continued bastardization of a term.

ISO absolutely is NOT an element of exposure.

And maintaining that ISO is an aspect of exposure leads to all sorts of misunderstandings. So, in fact, it is you, and all others who use the term "ISO" as an element of exposure who are making "very poor use of language".

If you consider the correct use of terminology to be "playing games", then it is you who is "lacking in integrity".

For a given scene luminance, f/2.8 1/100 ISO 100 and f/2.8 1/100 ISO 200 have the exact same exposure.

The reason, of course, is because the exposure is the density of the light falling on the sensor (photons / mm²), and the ISO setting on the camera has nothing whatsoever to do with that except when in an AE (auto exposure) mode, the ISO control indirectly affects exposure through the camera choosing a different f-ratio, shutter speed, and/or flash power.

Aside from that, the only role the ISO control on the camera plays is that higher ISOs increase the output brightness in an analog amplification to the signal (resulting in less read noise for non-ISOless sensors) and/or digital push.

Of course, if you want to think, for example, that f/2.8 1/100 ISO 100 has the same exposure as f/2.8 1/400 ISO 400 for a given scene luminance, that is your preogative, but, as others have informed you, you would be wrong.

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