P: Camera Raw: Canon R5 Raw images are underexposed

Lisa, would you like to send me a raw file - would be happy to examine it!
mail@ashmills.com

I need to look into RawDigger? thanks for the help!

Lisa, it is a known Adobe bug, they will fix it.

The process to create a variable ISO preset (hacking a text file) is hardy a simple process, especially if you have several variables that you tweak as you vary ISO.

Raw digger is lovely n all, but the in camera histogram is what people have to use on location. I have my cameras set up to match as closely as possible RAwdigger and what I get in ACR pleases my clients. Although they are not 1990s blue chip ones obviously.

I knew you’d bite at “scientifically” my point was they are “rawest” -looking without being shockingly ugly.

It isn't accurate. You like the current rendering which has nothing to do with the underlying data. 

Again, download a demo of RawDigger IF and only if you want actual information about raw exposure. I outlined a number of URL's above about exposing for raw. 
A JPEG that looks perfect on your camera could be a good 1-2 stops UNDER exposed. You simply cannot use LR/ACR and nearly any other raw processor to gauge raw exposure unless the Histogram is showing you the raw data, NOT a currently rendered image. 

You can have an image that looks 1-2 stops OVER exposed and it isn't. The articles above show this. But this one nails it visually ( Waterfall image):
http://schewephoto.com/ETTR/

There IS a bug with your camera and that's why it looks worse, but even when fixed; it's not accurate with respect to exposure of the raw data. Until ACR/LR provides a raw Histogram, you will never know exactly the conditions of the raw exposure. 

but why has it always been accurate prior to the R5?

It looks ' great' because that's a JPEG, and has little if any bearing on the raw data itself. The Histogram is the JPEG and tells you nothing about the exposure of the raw data; you need a tool like RawDigger to do that. This JPEG is built from the raw, using the cameras  proprietary processing. It has absolutely nothing to do with the raw itself or what another converter may render from that raw. 

Further, LR/ACR and anything but Canon's DPP will rebuild the camera JPEG preview at some point based on the raw data plus the current rendering settings of a raw converter. Again, now using that converter's proprietary rendering. 

Bottom line; unless you shoot a JPEG, the preview on the camera is mostly science fiction in terms of the actual raw data and what any 3rd party raw converter will show you of that actual data. The Histogram is a lie:

ironically the image in camera looks great!  exposed just as I wanted it, but way dark and nowhere near as vibrant as in camera either....  that is what isn't making sense to me!  I have always had my images appear on my computer as they have been in camera!!

As a quick sanity check please make sure that Highlight Tone Priority (HTP) and any other in-camera settings that affect exposure are set to ' Disable.' If enabled the images will look OK in Canon's DPP because it can read and apply those settings to the image, but the exposure in LR and ACR will appear incorrect. Can't hurt to check!

Adobe’s default NR and detail settings are far less than ideal for most uses, even if they are scientifically more accurate.

What is scientifically accurate NR default settings, how is it measured and defined scientifically and what software product provides such defaults? 

Can any default be less than ideal for most all users? I believe that's possible and why users are provided options to alter defaults or make their own. Subjectively. 

I don't find the process of setting up ISO presets unfriendly or difficult but I suspect those that haven't learned how may.