Z7 auto ISO seems seriously flawed

Started 4 months ago | Discussions thread
Alex Permit
Alex Permit Senior Member • Posts: 2,338
Re: Professional target group

Iliah Borg wrote:

Alex Permit wrote:

FingerPainter wrote:

Alex Permit wrote:

j2scriba wrote:

...This may be an acceptable design paradigm for a point-and-shoot, but for a presumably professional target group this seems bizarre....

There are three parameters that determine exposure:

Yes, but ISO isn't one of them. The third is scene luminance.

I'm not following you. Properly exposing for a given scene luminance is what you are solving for. The three parameters you change to accomplish this goal are shutter speed, aperture, and ISO. It's called the exposure triangle.

Are you saying 1/30 f/8 ISO 100 is the same exposure as 1/120 f/8 ISO 400? If you do, it contradicts the definition of photographic exposure. ISO speed is applied to scale the signal obtained as the result of the exposure, and it is applied after exposure is over. All those thousands and thousands of articles explaining exposure triangle got it wrong.

The triad is indeed formed by the light, coming from the scene and hitting the front element of the lens, reduced by the aperture opening, and acting during the exposure time.

Since each point of a natural scene emits/reflects light differently, proper exposure for a given scene can't be defined by one abstract figure, one needs to take dynamic range of the scene and of the camera into account and place highlights and shadows in correspondence with technical limitations and one's artistic priorities.

I understand you disagree with the thousands of articles explaining the exposure triangle, and are defining exposure as exposure the amount of light per unit area reaching the electronic sensor. I do understand and acknowledge this meaning of the term.

I assume you understand the colloquial meaning of exposure as outlined in those thousands of articles which indeed would say 1/30 f/8 ISO 100 is the same "exposure" as 1/120 f/8 ISO 400.

Would you acknowledge we are using the colloquial meaning when discussing "auto exposure" such as "auto iso", which is the topic of this thread?  If so, we are arguing semantics.  If not, could you elaborate.


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