This answer will seem a bit indirect, but I think it's best if we start back with some basics.
The point of a microscope objective is to cover a small area at high resolution. You can think of the Nikon CFI 10X NA 0.25 as being a reversed 20 mm f/2 lens whose design is optimized to run best wide open, resolving roughly 700 line pairs per mm but with that high quality only within a circle of roughly 5 mm diameter.
You can change the overall magnification by changing the length of the tube lens (rear lens), but that doesn't change the size of the high quality image circle
on subject.
How do you calculate the coverage of the objectives compared to the sensor?
The coverage of an objective
on subject is fixed by its design. Even for the best objectives this will be no more than about 50 mm divided by the objective's
nominal magnification. For most objectives it is significantly smaller, more like 30 mm divided by the nominal magnification.
This coverage on subject maps to coverage
on sensor simply by multiplying by the
actual magnification. If you run that Nikon CFI 10X at actual 5X by sticking it on a 100 mm tube lens, then the coverage on sensor becomes 5 mm on subject * 5X = 25 mm on sensor. This is why it covers an APS-C sensor at 5X, but not full frame.
is there a better objective that will cover the full frame sensor of the D800? I do not foresee myself needing an objective that is capable of more than 5x on my 105mm, but I do need it to cover the full frame sensor.
Yes, there are better objectives for 5X on full frame, but they won't be nominal 10X pushed down with a short tube lens. To cover full frame at actual 5X, you need coverage on subject of about 8 mm diameter. That calls for a lower magnification objective, a 4X or 5X, and then you'll be needing to use it on a 200 mm tube lens in order to run at actual 4X or 5X.
Arguably the best microscope objective in that regime is the
Mitutoyo M Plan Apo 5X NA 0.14, working distance 34mm.
However, the Mitutoyo 5X is essentially just a 40 mm f/3.5 apochromat fitted into the Mitutoyo standard objective mount.
So, it's a good question whether you'd be better off with the Mitutoyo 5X on a 200 mm tube lens, or better off with some other roughly 40 mm f3.5 apochromat used by itself on bellows. For discussion relative to that topic, see for example
http://www.photomacrography.net/forum/v ... hp?t=21874 and the links therein.
merge into panoramas
For some discussion of pano merging in macro settings, see our FAQ
What is "stack-and-stitch", and how can I do it?. There are some issues regarding parallax that you may not have run into yet.
--Rik
