Does that mean, for instance, that with a DNG where you edited the shadows down to nearly black for an abstract feel and the embedded preview is now showing that dark effect, that you can still dig into those ultra dark areas later on for a more natural look, becuz the sensor data is unchanged and still available ?

IOW is the sensor data in a DNG read-only just like in a true raw file, and is accessible for new editing just as with a true raw file ? Further, if you can re-edit from dark abstract to a well adjusted natural look, would that replace the dark abstract preview with a new well adjusted preview ? Seems there could only ever be one embedded preview at any one time.

Does that mean, for instance, that with a DNG where you edited the shadows down to nearly black for an abstract feel and the embedded preview is now showing that dark effect, that you can still dig into those ultra dark areas later on for a more natural look, becuz all the original sensor data is unchanged and still available ?

If the above is affirmative then is there in some way any less potential in a DNG than in a proprietary camera raw file, or are both types essentially equal ?

IOW is the sensor data in a DNG read-only just like in a true raw file, and is accessible for new editing just as with a true raw file ? Further, if you can re-edit from dark abstract to a well adjusted natural look, would that replace the dark abstract preview with a new well adjusted preview ? Seems there could only ever be one embedded preview at any one time.

In answer not only to this, but previous posts: Tiff is not equal to RAW in terms of processing potentialities. Tiff is an image file, not a pure data file. It is a universally recognized image format that defines each pixel in terms of its chroma and luma values, so that any image-displaying application will know how to color and light each pixel in the image. RAW is raw sensor data, and pixel values exist as potentialities in relation to each other. Once those values are defined and fixed by an image editor, then all the other potentialities are discarded.

Consider a print from a negative: no matter how good a print is, making another print by taking a picture of that will never have the potentiality of printing again from the original negative. But you can't display the negative, or even see the image really. You need a print. Think of the Tiff (or a jpg) as a print. The Tiff has much more data stored, and is not lossy, meaning that pixels are never defined as clumps, but as individual pixels. You can save a lot of space by defining groups of pixels together and giving them the same values. This is what jpg does. Tiff treats pixels as individual.

But there is another level here, and that is bit depth. Tiffs can be saved as 8 bit of 16 bit (also 32 bit, but that is a different story). 16 bit Tiffs still define pixels individually, but with more accuracy. Instead of having one of 256 values, it defines each pixel in terms of 65.536 discrete values for luminosity and for each color channel. It is like having much more resolution. Therefore 16 bit images are much more amenable to post processing, because there are many more in-between values for each pixel.

The reason to make a Tiff is so that you don't have to make it all again from scratch from the RAW every time you need it. And the reason to make it Tiff is so that it is the highest possible quality, that will not further lose quality with subsequent adjustments. Personally I always keep the RAWs, but then I have separate folders of 16 bit Tiffs, so if someone requests an image for some use I can pull it from there immediately. 16 bit Tiffs can be processed pretty radically for different uses, for example if they are needed lighter or darker of with slightly different colors. And all those images are immediately viewable without having to open in a raw editor, which displays them according to its own interpretation of what the pixel values should be. But even so, and even though 16 bit Tiffs are much larger than RAW files, they do not have anywhere near the potential for editing that RAWs do.

First, NO, I don't have Elements.

My editing experience is limited in some ways. I have mostly worked with JPG files. But I have encountered times where I have seen lost detail in shadows, or the darker portions of the image. So I experimented with DPP4 on a RAW file but got no better results. I suspected that DPP4 may not be powerful enough, or I'm not familiar enough with it. So I thought I might try converting the RAW file with DPP4 to something lossless then editing it in another editor. My copy of Photoshop is quite old, it is version 7 and I haven't even tried to work a RAW file from my 80D thinking it wouldn't have the CODEC.

Yes, that's will be an effective way to work and can give you equivalent access to the shadow detail compared with using a raw processor that works with the raw file directly (DPP works with the raw file directly.) Given that DPP knows what Canon knows you may in fact come out ahead.

You need to set it up in DPP to start when creating the 16 bit TIFF.
Get the WB right.
Set the Picture Style to Neutral.
Click auto in Gamma adjustment and then go to the histogram and pull the left limit (triangle) as far left as it will go.
In Advanced make the Shadow value 5.
Back to the Gamma adjustment histogram and consider pulling the midpoint slider to the left -- the photo will get lighter and the shadows will continue to open up. Exercise discretion but you want to end up with a too light and flat looking image.
Save as a 16 bit TIFF and head for Photoshop.

I'll do an example and post it.