Raw histogram and why does it matter

@DonaldB

Are you still claiming one of those histograms in your op are a histogram of the actual raw data in the raw datafile?

A simple yes or no will suffice :-)

That Adobe article as well clearly shows the histogram in ACR is not a histogram of the data in the actual raw file. It says the ACR histogram is a histogram of the processed raw data.

You are actually unknowingly, because you most likely haven't read either article, posting evidence proving you were at best naive at worst foolish in trying to pass off the ACR histogram as a raw histogram.

To summarise this thread:

To me the "Fiddlers" bottle reflextions look like clipping, while the RAW data shows none. What am I missing?
And the brush also.

Exactly.

Thanks for your intervention.
I acted discretely way before, without being listened :-(

Fair enough. Point taken and I have deleted the last line. It was my Bad.

This file is about one stop underexposed from ETTR, assuming a 14 bit ADC.

Well, I see we're enjoying the more open environment here in this DPR spinoff forum. That's good. I wouldn't want to see your post deleted or the thread locked because of it, which would have happened with your post in the Canon R forum at DPR. In the spirit of free exchange, I would say that questioning of Donalds's photographic professionalism is irrelevant and unnecessary. There are plenty of people who deliver professional quality photographs consistently to clients, who don't know much about what data and math goes on, under the hood, in a camera. There are probably also people who are so intimate with the workings and properties of raw digitization who could write code to remove known artifacts from raw files, who would be a risk as an event photographer.

You make valid points and to help alleviate people's concerns this thread has had a hidden benefit as well.

DonaldB and I just finished going through a mediation process with Admin and from my point of view it went well as it resulted in a positive outcome for both of us. I feel the mediation was a good test case.

The mediation process was much better handled than the heavy handed moderation that would most likely have occurred if we were still on dpreview.

Hopefully the mediation process will be adopted and successful here on dprevived.

We can go back on topic now :-)

Jim,
Why is the number of bits in the ADC relevant here?
Where does the "one stop" come from?
Thanks
Sherm

Yes, there are a few small things to know when interpreting a raw histogram. You want to know what raw level data actually starts clipping at (which is often not the max value of a bit depth), and also, what raw level data becomes non-linear at, if a camera offers part of the non-linear range. My first DSLR (and my first camera with raw files), the Canon 10D, went non-linear in the highest raw values at ISO 100. ISO 200 clipped at about 22K electrons, but ISO 100 clipped at about 55K, 25% more than expected based on ISO 200. Some people had stated the FWC of the 10D at about 44K, but apparently they looked at SNR well below clipping and just extrapolated the FWC from that without checking for non-linearity.

I thought your post that I replied to was very recent when I replied, and didn't realize that it was already addressed. I wouldn't have replied if I realized that.

No problem. As I mentioned, you made valid points.

It isn't just a difference in level, either. Some raw "colors" explode when converted to display RGB, like red tulips, which can easily flood the top of a display RGB histogram and detail-less magenta areas in the image, but show little "energy" in the raw histogram from the red tulips.

It is useful, but not as useful as a raw histogram when you want raw ETTR without unwanted clipping.
If you are only interested in an actual ISO 100 exposure index when the camera is set to ISO 100, then by all means, look only at the histogram of the in-camera display image; it won't steer you wrong.

I'd think that my final image would look like display RGB. If that's the case, your last statement suggests to me that I should take the in-camera histogram more seriously, not less.

No, it didn't. Accuracy of RawDigger is why not only photographers, but also labs, universities, and camera-manufacturing companies are using it.