Mike, good questions. I used Aperture Priority and an f stop of f8 when I took the shot. To focus in Live View I moved the focus square usually to the subject's eyes or other part of the image I wanted in sharp focus. I chose S in all of the shots as best as I can recall. Then I used the AF ON button. White Balance was set to Daylight most of the time.
1) If you shoot from the back (shiny) side, you do not have to flip the scan. That works well for me with both slides and negatives. I focus on the grain, so there's no difference in sharpness. To manage Newton's Rings In a scanner (which reverses the image), it's best to place the emulsion side toward the lens. Film usually cups toward the emulsion side, so emulsion side down only touches the glass at the edges. The back is against anti-Newton (textured) glass. 2) The best way to focus is connecting a monitor to the HDMI port of the camera, with HDMI Data minimized and enabled. That way you can use the magnification focusing option, which makes focusing on the grain easy, with minimal handling of the camera rig. Theoretically AF cannot work at 1:1 reproduction. Even manual focusing is problematic. I back off the lens focus a bit, rough focus with the tube extension of the ES-2, and finish with the lens. That might be enough to allow AF. AF works easily with a DX camera, because the reproduction ration is 1:1.5. 3) I use "Negative Lab Pro" inversion software . It's a plugin for Lightroom, and works directly on RAW files. Like other adjustments in LR, it is non-destructive. I scanned over 1000 images in three two-hour sessions last week with near perfect results. I don't have a D850, but Photoshop has a negative conversion option, which works poorly. 4) I agree. If you set the WB with an empty holder, results are not affected by difference in the orange mask, nor by predominant colors in the image. An LED Daylight replacement bulb works well. For my marathon conversion sessions, I used a small CRI 95 light panel by LumeCube, set to 5500K. 5) "Negative Lab Pro" works with any camera, RAW, TIFF or JPEG image, in Lightroom. I straighten and crop each image (which takes the most time), the process the images in a batch. It takes about one minute to process three rolls (>100 images).
Film has curvature, and there's not much you can do about it. Slides bulge in the center towards the backside. Film strips tend to curl, especially at the ends, even when stored flat in archival polypropylene pages. So how and where do you focus? First of all, use the camera in live view mode. Sony (and all mirrorless) cameras are 100% live view. Sony offers focus magnification of 5x or 12x in a spot you can move around with the joy stick control. Film curvature can exceed the meager depth of field near 1:1 reproduction (I use f/5.6, or never beyond f/8). I usually take the easy way out and focus in the center, roughly at full frame, then successively at 5x and 12x for grain sharpness. At times I have focused roughly midway between the center and one corner. While easy enough to do, I don't find it helps much. The exception is when the image is not dense enough at a particular location to see the grain. Besides, the most important detail is near the center, and the corners generally less so. The ES-2 clamps to the sliding tube with a thumbscrew, which proves to be quite stable against the extra handling when using film or slide holders. I check the focus from time to time, but it doesn't change much in use. Out of 6 frames, I focus on frames 2-5 rather the ends. If I see significant curl, I focus separately at the ends. Using a monitor (which can be a TV set) makes focusing very easy and quick. More important, a monitor makes straightening and centering the image more precise. The ES-1 film holder does not have a clamp screw, and can twist or slip if mishandled. In practice, that's not a problem if you are reasonably careful. Furthermore I find the ES-1 much quicker to use than the ES-2 when copying slides. You cannot copy film strips for the ES-2 without touching the film in an image area when loading the holder and centering the film.. As a precaution, I use cotton "inspection" gloves, which are cool to wear and nearly lint-free. After loading the holder, I use a blower to remove any lint, or better yet a small anti-static brush. I clean each side upside down so that any debris falls away. That seems to work very well, and I rarely have to re-scan an image because of dust (<1 in 100). https://www.amazon.com/dp/B0000AE67U?psc=1&ref=ppx_yo2_dt_b_product_details
It depends on what you want to do. Slide mounts have an opening a little smaller than the image on the film, and even if they don't, many have rounded corners. If you want all image and no mount, you need a little more than 1:1 magnification. Or you can crop after the shot. If you want all that is visible, then 1:1 or a little less. Sometimes I like the rounded corners to be visible, as it reminds me that the original is a slide. And it is different in the case of negatives, again depending on what you want, and a little depending on the actual size of the frame from the camera.
I just started using an ES-1 with my 55mm f/2.8. I must say, I'm disappointed in the amount of play in the lens's front inner barrel that this usage has revealed. When the lens is fully extended (at MFD), the front barrel, with the ES-1 attached, seems to sag on the order of half a millimeter due to the added weight of the attachment. This throws the alignment of the ES-1 off enough that I am forced to push it up with my left hand in order to center the slide on the sensor before taking an exposure. Does anyone else have this problem with their 55mm f/2.8 when using an ES-1 or ES-2? Perhaps my copy has loosened over time.
I use the ES-2 with a 55mm/2.8 AiS and find absolutely no play in the barrel when fully extended - not even when I put pressure from side to side.
My AI 55/2.8 wasn't used for some years, and the focus ring is very hard to turn. I warmed it up in the sun, and it softened up a little bit. I believe it doesn't sag, either, but didn't really test that. I have only used the ES-1 a few times, and didn't try so hard to get the centering right. I have mine on a D700.
I stopped using a modified ES-E28 with my 55mm f/3.5 Micro-Nikkor because of concerns about the strain it placed on the focussing helicoid. My f/2.8 micro-Nikkor came to me 'pre-abused' and already had some slop in the helicoid that needed support with the copier attached. I now use an 'Illumitran' purpose-built copying rig fitted with an enlarging lens. And get sharper copies. However, on further thinking about it, the strain on your lens could be reduced simply by pointing the rig vertically downwards. This might need a re-arrangement of your illumination source, but should automatically centre the lens better.
