I know all that. I was wondering – only for mirrorless – whether the RAW file still is pure data, regardless of what appears on the camera viewfinder/screen as changes are made. If it is still just pure data, then there would be no advantage in being able to see an adjusted picture (which would be jpg only) prior to taking the shot – unless you were going only for jpg!!! And if it were not pure data, then there would be no advantage in shooting RAW in a mirrorless camera – where in essence you would be doing your postprocessing on a tiny camera screen, and lacking so many “bells and whistles”???

Loren – in Beautiful Baguio City

I think this was covered before in the many "DSLR vs. Mirrorless" debate threads. Yes, a DSLR or SLR will give you essentially a real time speed of light preview of the image, whereas the EVF image of course is a tiny monitor inside the camera of what the sensor sees**. A mirrorless camera is basically a video cam. You are basically a videographer if you are taking stills with a mirrorless - you're just picking out the frames. There are certain pros vs the few cons of mirrorless....one is exposure preview - that is something impossible to do with a DSLR. The tiny bit of lag/blackout is inconsequential in the vast number of use cases, and some recent models (like the Z9 or high end Sony's) have brought that down to practically nil. With a DSLR low light can be challenging, but with mirrorless that is a piece of cake, plus you are getting an accurate exposure preview. The art of photography is not lost, the photographer just has to make a small mental adjustment to the new tool. As time goes on the petty differences between DSLR and mirrorless will become less and less of an issue for discussion as technology improves. We are witnessing the end of the DSLR era and approaching the golden age of mirrorless.

** What I would really like to see is instead of a tiny peephole on mirrorless cameras is a somewhat larger EVF or viewscreen on the back of the camera with a small light hood. There is no need in this day and age for photographers to look through tiny peepholes! Eye relief should be a major priority. Think the waist level viewscreen on the old Hassy's only on the b ack of the camera. Of course the LCD screen could be used with a hood attachment, but higher resolution would be needed.

There is one consideration that is rarely mentioned in these mirrorless vs. DSLR debates: investment.

Investment, really has nothing to do with the comparison. Technology moves on independently of all of us and our abilities as photographers. Technology never makes you a better photographer , but can make some things easier, faster or better in some way.
If you are happy with the equipment you own and it produces the results you want, you should feel zero pressure to change. The D850 is one of the best cameras ever made, if you went looking for something you cannot do with that camera you would be hard pressed to find something.
If you decide that some of the features of Mirrorless better suit your style then add a body, if you are happy with your D850 use it and don't worry.
There will ALWAYS be something new.