ISO & Dynamic range - what is going on?

it appears to have less noise because you have not changed the exposure. so an image taken at iso 100 is going to be underexposed so when lifted the image has more noise than the properly exposed image at iso 2000 ,the 2000 iso image has activated the dual gain amplifier , its basically turned up the voltage, same happens with microphones that are battery powered or auto gain radios that increase the RF signal before it hits the audio preamp.

forgot to add that more information can be captured/stored in the highlights than the shadows 🤔dont ask me why its just because 😁

Incorrect.

Correct: www.photonstophotos.net/Aptina/DR-Pix_WhitePaper.pdf as Arvo says.

This may help with question 2)

chatgpt.com/share/6862d7f6-7e60-8013-9ac3-aa25091a3bd0

Incorrect?

(Underlined for emphasis, no less). Posting is a death sport on the Internet. Calm exchange of ideas is impossible.

Hmm . . Well at least you edited out the exclamation points that were there earlier.

This excerpt from your link is equivalent to my explanation. (Italics added for emphasis)

"Many approaches to increasing DR focus on achieving
high intra-scene dynamic range. However, these HDR
techniques do not improve low-light sensitivity or reduce
noise to improve low-light image captures. As a result,
a different approach has emerged to improve inter-
scene DR and sensor performance through the addition
of a high-sensitivity mode to the sensor’s operation.
Two modes are combined in one pixel design – low
conversion gain (LCG) for large charge handling capacity
in bright scenes and a high conversion gain (HCG) mode
with increased sensitivity and low read noise for low-
light scenes"

You may have the thread to yourself. I have enough practical experience in designing and implementing both analogue and digital electronic circuits and A/D conversion systems to be confident in my explanation. I enjoy discussions and especially enjoy learning something new. But I intensely dislike MMA style responses to a disagreement of opinion.

Maybe you can get that anger under control.

Rich

Maybe you're right. If someone posts incorrect stuff, maybe it should just be ignored, thereby joining the wealth of false information on the 'net and leaving Alan none the wiser as to what "dual gain" is.

I don't know what "MMA style" is.

As regards "dual gain" my original response to Alan was this and no more:

There is a technology licensed by Aptina which applies extra capacitance to each photocell requiring more exposure for a given scene, if so applied.

Since ISO(SOS) = 10/(mean exposure) for a mid-gray output, the effective exposure index (ISO number) is reduced when extra capacitance is applied.

A direct personal insult worthy of the Dumpster, I reckon.

Alan, The Aptina method adds a fixed value of capacitance to the photosensor at low ISO settings, hence the term "dual". That lowers the "gain", meaning that more exposure is needed for the sensor to give the standard output (mid gray). See kronometric.org/phot/std/DC-004_EN.pdf for what the standard output is.

Terminology: the extra capacitance cuts out, not "in", above a certain ISO setting.

Generally speaking in photography the more the exposure, the higher the Signal-to-Noise Ratio, meaning less noise relative to the signal.. This affects the meaning of "less noise" in your question above. In photography there are a good few parameters which are relative to something but, when expressed as values, often get the qualifier "relative" left out by authors.

For example, *I shot with an aperture of F4 * (using the common fighter-jet format) when most people say "f-number" or, even better, "f/number".

Which brings us back to slower readout sensors provide better quality images. one of the main reasons sonys new fx2 has gone with the 33meg sensor from the a7iv. to many photographers think that faster is better but im afraid thats not the case if IQ is your main objective.

I was talking to Alan, not you. Obfuscating my post with talk of read-out speed and MP is of no help to Alan at all.

Of the original question, I offer a slightly different take. I would hazard that when designing the response of the sensor they were aiming to have a visual consistency to the results. It would be awkward to have a camera that has an auto ISO setting that shoots one exposure at ISO100 and half a second later the same shot at ISO160 and have them visually different.

Now this may be that using "dual gain" (a guess based on answers already in this thread) gives them an optimal performance but does produce a slightly wavy line on a graph.

Back to the first point of visual consistency, and the assumption it was achieved, then is there any relevance other than curiosity? The danger of looking in the n'th degree at technical details is that we will naturally attach an importance and relevance to our understanding, and to some extent try to apply that understanding in our photography to justify our knowledge.

The point being that if we look at graphs and attach an importance to the different theoretical noise levels at say 100 and 160 ISO and start using that to influence our exposure settings, then we are effectively missing the point that the camera is designed to give visual consistency. Or in other words we look at the numbers and see differences while we fail to look at the actual pictures and notice that there is no difference. If we just look at absolute data then we tend to think of photos as absolute things that reflect the absolute data recorded by scientific instruments and miss the understanding that the human eye is not a scientific instrument by a long chalk. Just because a graph can highlight an absolute difference does not mean there is a visible difference to the human eye.

Just so's we know, Alan's posted graphs in question are not showing "theoretical noise levels" vs. ISO.

Here's a noise graph for a Canon FWIW