Z7 auto ISO seems seriously flawed

Started 4 months ago | Discussions thread
Iliah Borg Forum Pro • Posts: 26,080
Re: Professional target group

Alex Permit wrote:

Iliah Borg wrote:

Alex Permit wrote:

6michaeladawson wrote:

Iliah Borg wrote:

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.

I agree with Iliah here. ISO is not part of exposure. As Iliah says, it controls what the camera does to the image after the light has been captures (the exposure). Look at ISO invariant sensors. You can shoot at base ISO and increase exposure in post.

The exposure is done by setting aperture and shutter speed to capture the amount of light you need. Adjust shutter speed and aperture to also capture the "artistic" effect you want (motion blur/freeze, DOF, etc). Raising ISO is just an after the fact adjustment when your chosen exposure doesn't result in the necessary image brightness.

Almost like taking a CD or vinyl record that has an "exposure" recorded on the disc and then using the volume knob to adjust the "brightness" to your listening taste.

If I were to include image noise (or lack thereof) as part of the artistic effect then indeed raising ISO does effect the image.

Raising ISO, given the exposure is the same, makes noise quieter, or doesn't affect it at all.

Raising ISO and using an "auto exposure" mode

This makes so little sense.

(the topic on this thread)

Happens a lot

would reduce the "exposure"

It reduces the exposure, no quotes needed.

and raise the noise.

That's the whole point. Reducing exposure increases noise, raising ISO can only mitigate that noise increase, to some extent.

Exposure triangle and that "colloquial" meaning of exposure, where 1/30 f/8 ISO 100 is the same exposure as 1/120, f/8, ISO 400 puts everything on its head. It incorrectly connects noisiness with ISO instead of making a direct connection of noisiness with photographic exposure.

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