Focus Assist uses the Phase Detect AF system (PDAF) to establish communication between the lens and camera, so it can produce focusing errors if a particular camera and lens is out of focus. Setting in-camera picture controls for jpegs assumes that neutral on one camera is the same as neutral on another. They may be close, but not necessarily the same. Each camera sample has a unique color response - even for raw capture. Using a target like an Xrite ColorChecker Passport, will let you create a neutral camera profile that would result in color and exposure (I think) to be virtually indistinguishable from one camera to the next. When shooting events with second and third shooters and multiple cameras, I would create color profiles for each lighting scenario for each camera. It's bit of a pain, but it worked like a charm, saving hours of post processing. Also, any change in the lighting would result in differences in color balance and exposure - radical ones - especially if overcast.

The D700 is 4256x2832 px. The D850 is 8256x5504px. You would use software to resample the D850 so that the pixel count on the longest side = 4256px. There is no magic here, other than noise and image quality often improves when downsampling a high MP camera image - but comparing images of equal size is important to your illustration.

You are using a D lens- screw drive focus. Every body and lens have different focus engine and different results. The 7000 I couldn’t use not every lens, certain lenses would hunt the focus with inaccurate focus. Following I had to learn: I have the 70-300mm 5.6- VR the focus engine broke (read reviews on eBay) and after the repair this lens works way better than new!- Nikon used a leftover engine from a other lens even wasn’t strong enough. Later my 7000 focus engine slowly broke down too-comment problem, too. The 17-55 2.8 DX lens what will still focus properly on my broken 7000! Just took longer.
On my 810 every lens I have focus probably but not every lens will focus probably on different camera body’s. It’s not 100% accurate either because the 50 1.8, 70-200 2.8 and 17-55 2.8 will get focus probably done no matter what body.
I don’t know if your test and my experience are on the same page. I’m wondering how the 80-200 2.8 D works on different bodies.
I hope your 810 doesn’t have a damage.....

Here are three items that must be considered when testing “sharpness”:

1. By shooting outside you are shooting in an uncontrolled environment where a slight breeze or a thin cloud passing over or sun movement over the time the shoot took place can change the resulting sharpness.

2. Focus - in comparison tests do not trust autofocus - tweak focus each time - if you trust autofocus your test probably tells you how well the lens/camera autofocus combo works and not how sharp the lens/camera sensor is.

3. When testing different size sensors for sharpness the distance to the target should be adjusted so the target occupies the same area in the view finder for both sensors. Less distance for FF sensors than APS-C sensors for example.

If you keep the distance the same you are testing the resolving power of the lens not the sensor.

Hi Gene51. Please educate me. If the 850 images are downsampled they would be sharpest in the bunch since when you downsampled a large image does it not improve sharpness of the image? I'm ignorant of a lot of those practices. I shoot and look at my images at 100 percent and if sharp I'm happy. I tune my camera to my lenses and print a small amount. I understand the color management system so my prints match as close as possible. I need education in effects of downsampling. I'm sure now I have no choice but to read. Lol. I figure you can tell me the basics since I just got up. Lol lol. Thanks Bob