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Photography DiscussionUnvariant sensor

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Unvariant sensor

Post by English_Wolf » Wed May 25, 2016 4:06 pm


I started a conversation on another board over this 'new' feature (2011, really).

The understanding of it seems mostly a bit fuzzy unless you are an electrical engineer.

I am not an engineer so my understanding is all relative to what I have been reading.

Basically a 'variant' sensor uses the ISO setting to augment the sensor sensitivity by raising the voltage to it and capture the result.
An 'invariant sensor' use the camera processor to modify the capture from a set ISO that really never changes. The value instruct the camera processor to process the capture brightness.

In case one (variant), we have been relying onto the sensor DR and various methods like ETTR, EBTR and ETTL and PP to achieve an acceptable result. Some of us even use uniWB in order to get a true histogram out of the camera.

In case two (invariant) we just need uniWB and PP. We still use the camera DR at its nominal/optimal value meaning that it does not change or degrade as it does in case one. I am not sure what this will do the color accuracy.

In short, shooting at the optimal DR ISO value is all that is needed and PP the image ourselves seems to be best.

Now, can anyone correct my understanding, and set me right because I am almost certain that I missed something.

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Post by St3v3M » Mon Jun 06, 2016 5:18 am

It's a curious question and one I'll be curious to see if anyone has anything to add. S-
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Post by Duck » Thu Nov 09, 2017 1:19 am

I'm not really understanding what your question is here. As I understand it, variant vs. invariant is about getting a desired exposure out of the camera based on native sensor technology (some handle signal amplification better than others). How the camera uses that technology will then determine which exposure technique will work best during and after the time of exposure, like ETTR, UniWB or just simple old fashioned PP with exposure correction and noise reduction, during capture.

I have noticed that the old mantra of shoot at the lowest possible ISO doesn't always give you the best results. Different lighting circumstances will dictate which shooting technique will work best. Factors such as subject activity play an important role, specially if you are looking to implement a base ISO/boost exposure later workflow. A lower ISO may require a slower shutter effectively creating too much blur on a moving subject. Raising the ISO negates the base ISO/boost exposure later workflow but gets the desired effect in camera.

As for a good explanation of ISO invariance, I found this article; ISO Invariance Explained
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