Exposure is not how dark or how light an image looks!

Light meters don't need to be perfect, just reasonably accurate and consistent. They generally work very well and, as the user's understanding of them improves over time, any good meter can produce reliable results.

Why would that be a problem? Each one may have had different intentions but so what?

Indeed. I use my camera's highlight-weighted matrix metering most of the time, which automatically kaboshes any (currently-available) automatic use of a tone curve. I've accommodated this in my post workflow, so it's not a big deal.

I think it is quite common for photographers to omit scene luminance when discussing exposure. ISO is properly omitted, because ISO has no effect on exposure. Lastly, exposure by itself has great meaning, if you understand how it works.

I think it is sad that so many photographers shooting raw and trying to get the best exposures don't ever look at their files with a program like RawDigger. If you don't know what the raw data looks like, you are just winging the exposures. I don't think you have to look at the raw data for every image, but I think you should routinely look at it so you can see how well you're doing.

Edit: not sure why this was posted twice. The first time I got an "unknown error" message.

It depends on your goal. If your concern is the underlying numbers, then RawDigger is a useful tool. If your goal is producing an image with no visible noise, then your eyes may be able to tell you whether or not you have reached your goal.

In some sense it’s like putting water in a bucket. Once you have put enough water into the bucket, pouring more in doesn’t make the bucket more full. Once in image reaches the point where there is no visible noise, further reductions in noise don’t change the appearance.

If you have a five gallon bucket, pouring 6 gallons of water gives you the same result as pouring in 60 gallons. You end up with a bucket that is full. It’s not that 60 gallons gives you a better result. Once your image quality is so good that there are no visible issues, then you can make a reasonable argument that further measurable improvements yield the same result, not a better result.

By (my) definition, it is the exposure that met their intentions.

So if I say that under or over exposure is the one which was too low or too high to meet their intentions, you would be fine with that?

You could be routinely underexposing from ETTR by two stops and getting noise quality that you consider acceptable. If that were true, you could get the same noise with a smaller sensor and save your self a lot of money.

You could see noise in your image and be unsure about how to fix it. Looking at the raw data could tell you why your image is noisy and what to do about it.

I can't count the number of times people have told me that they are masters of ETTR and they know it by looking at the histogram in Lr.

One can also see (or not see) poor definition in shadows or distorted colours and be sure this is how it should be, or spend money on a camera that promises half a stop of "DR" improvement, f/1.4 lenses they nearly never use fully opened, etc. ;)

From a noise point of view, you can turn your full frame MILC or SLR into a micro four-thirds camera by underexposing by two stops, into a point-and-shoot by underexposing four stops, or into an iPhone by underexposing by six stops. Underexposing in this case is relative to ETTR.

Thanks!

Hear, hear. You are preaching to the choir.

It's very possible if there are red flowers in the scene.
Don

Consider a photographer working in the field. I choose an f-stop I believe will deliver an acceptable depth of field (DOF) and a shutter speed that will render movement to my liking. I know that those camera settings, combined with the available light, will determine exposure.

Based on an ISO of 400 producing a pleasingly light image and their camera's base ISO of 100, I also conclude they camera is roughly 2-stops below an exposure that would saturate the sensor without blowing out highlights.

Several questions go through my mind. What's an acceptable margin for error when assessing DOF and motion blur? The LCD display offers finite image scale and resolution. At best, it approximates how those image qualities will present on a larger monitor at home. I may consider it prudent to err on the side of settings that over deliver at least to some extent.

What does my experience photographing similar scenes tell me about settings that will both fulfill my desired goals for DOF and rendering of movement while capturing enough light to minimizing the negative impact of shot noise on the final image? As I gain experience and confidence in my field assessment, the narrower the margin of error I may require.

For example, using my lens at f/5.6 will deliver an acceptable DOF and images having good sharpness of a bird in-flight. I can leave the lens wide open (f/5.6), get the DOF and image sharpness I want and use that setting to maximize exposure.

I make use of tools and resources that are readily available and have proven to be of use in the past. In the field, I rely on knowledge, experience, and the camera's tools. At home, I can add Lightroom Classic's tools to the mix.

Assuming my ultimate goal is to produce a pleasing, high quality image, how would adding RawDigger to my existing workflow contribute to that effort. Where would it fit amongst my other tools?

You said "Based on an ISO of 400 producing a pleasingly light image and their camera's base ISO of 100, I also conclude they camera is roughly 2-stops below an exposure that would saturate the sensor without blowing out highlights."

You are drawing conclusions about how much headroom you have in the raw file based upon how nice the JPEG preview image looks? In your scenario, I don't see how you know much about the raw data. Actually looking at the raw data after the shoot would give you knowledge that you could apply next time you were in a similar situation.

I'm assuming the other questions beside those in the last paragraph are rhetorical.

Have you ever looked at the raw data for your exposures? If so, were you ever surprised at what you saw?

Also, I think your goal for the raw file should be not to produce a pleasing, high-quality image, but to produce a file from which you can construct such an image. The distinction is important.