Comment by zipy124

I actually used to design image sensor chips. The dynamic range is due to the electron well size. Each pixel has a diode that stores typically between 10,000-100,000 electrons in them. When the shutter is open, each photon that arrives pushes out an electron across the diode. When the shutter closes, sensors count how many electrons remain. This is how they calculate how much light each pixel received.

The well size itself is usually a function of the pixel size. A larger pixel means a larger diode that can store more electrons, and hence a larger range of light that can be measured - dynamic range.

What we're doing here to get higher SNR, generally, is growing the CMOS sensors larger and larger. The limitation is ultimately either depth of field or IC manufacturing issues. A hypothetical meter-wide sensor could be manufactured to combine with a catadioptric lense of extreme cost, but you'd expect most of a scene to be bokeh, like in macro or microscope lenses.

In reality there are limits imposed by manufacturing. At the extreme, we have wafer-scale sensors used in, eg, night-time wildlife videography - https://www.imdb.com/title/tt11497922/ . Anything larger than that is typically a not-perfectly-contiguous array of smaller chips.

You can also cryocool the camera, at the expense of weight, versatility, and complexity. Most astrophotography is collected with cryocooled CCD or cryocooled CMOS sensors. This helps much more with long exposures than it does with video, but it does help.

> Digital is mostly limited by bits, since a 14 bit image with a linear tone curve will have at most 14 stops of info right?

Bit depth ≠ dynamic range.

The dynaic range is about the highest and lowest value that can be measure ("stops" are a ratio per log_2, db are a ratio per log_10):

* https://en.wikipedia.org/wiki/Dynamic_range#Human_perception

* https://en.wikipedia.org/wiki/Dynamic_range#Photography

The bits are about the gradation with-in that range. You can have 12-stop image recorded using a 10-bit, 12-bit, 14-bit, or 16-bit format.

And at least when it comes to film, it is not a linear curve, at least when you get to the darkest and lightest parts. That's why there's an old saying "expose for the shadows, develop for the highlights"

* https://www.youtube.com/watch?v=rlnt5yFArWo

* https://www.kimhildebrand.com/how-to-use-the-zone-system/

* https://en.wikipedia.org/wiki/Zone_System

> The limitation is not usually the film itself but the development process' used

I respectfully doubt that, development process is a combinaison of techniques that lets you do many thinks with your row data and the line between that and special effects is quite blurry (joke intended).

One way to make HDR-like with films and cheap-not-advanced material is to do a several development of the same film to the same paper, with different exposures parameters. That way you combine different ranges of the image (eg stop 1-4 + stop 4-10 + stop 10-18) to produce you final image. This is a great craft workship.

The only limit is the chemistry of the films used (giving grains at almost nano scale), multiplied by the size of the film.

Side note: development is basically a picture of a picture (usually) done with different chemicals and photographic setup.

20 stops dynamic range is about the human eye's range. Achieving that for digital capture and display would be mind blowing.