The objective focus is not as finicky, but it is pretty quick. Either you are in focus or you are not.
I don't know about the original HD38, but if I am understanding you, then yes, it is improved on the auto calibration.
Detection range is given at 850 yards (meters), IIRC. That is for a human-sized target. Humans are sort of uniquely shaped and taller. I haven't had the chance to do much longer range work at known distances, most of the longer range work being from a vehicle on the road after an evening hunting. But I will tell you what I have seen at known distances.
Keeping in mind that the following terms have these meanings...
Detection - you know something is there
Recognition - you recognize it as a particular group of creature (e.g., human, canid, lagomorph, etc.)
Identification - you recognize it as particular types of animals or group of humans.
Sometimes, there is some blending of categories and sometimes there is little between detection and recognition.
I have detected raccoons and armadillos at over 200 yards as tiny moving dots, but identified them through night vision. By anatomical features, identification is closer to 50 or 60 yards, but by behavior (how they are moving), at over 100 yards. Raccoons and armadillos are very similar in size, hunched back, etc., so just standing still in a field, they can be hard to distinguish from one another.
Rabbits are smaller (cottontails), but are uniquely shaped. They can be identified out to at least 50 or 60 yards, but identified by behavior at well over 100 it they are running/hopping. Probably the furthest I have detected one is close to 175 yards, though I am sure they could be seen further, but are so readily obscured by brush.
Bobcat- detected one last night at roughly 150 yards as it was walking away from me and then it turned sideways. It took a bit of study to determine what it was (the question was bobcat/coyote/fox), but once given the right profile could be positively identified by anatomical features at that distance. We watched it move around and out beyond 190 yards where it was still recognizable (by behavior/locomotion) at that distance.
Deer- no problems recognizing a deer at 250 yards as a deer. I could not have told you if it was a particular type of deer and with antlers small on a lot of the bucks right now, could not have told you if it was a buck or a doe. 250 is the furthest known distance I have seen deer. Inside of 175, I can make out short antlers (looks like too many ears). At 200, I can identify bucks with racks where they are starting to branch. Right now, the growing antlers are vascularized and so are relatively warm and stand out nicely on thermal.
Large Owl - detected in tree at 195 yards, identified with NV as an owl. Could not tell it was an owl, but saw it fly and so recognized it as a larger bird with the HD38s.
Mice/rats - 130 yard behavior recognition of them crawling up and down tree trunks
Dove - detection at 120 yards, identified via NV
Hogs - the longest known distance I have seen a hog is 130 yards and identification occurred by anatomical feature. I know I have seen hogs in pastures beyond 250 yards (but I don't know by how much) where they were half hidden by grass and determined what they were by how they moved despite not being able to see them in their entirety.
Cattle can be detected at over 1000 yards.
That is about all that I have from my notes so far. The distances are based on landmarks measured on Google Earth from my position. This is not to say that these are maximums, only that they are what I have been able to put to paper so far. For most of my hunting, being able to see beyond 250 yards is usually not possible because of trees.
From what I have experienced with other thermal scopes is that depth perception through the scope is usually quite poor and it can be very difficult to assess size of the creature and distance away without having some idea of landmarks and their distance from you. Driving around with Glenn Guess and watching for hot spots and not realizing that the tree line was merging with the road and calling out a STOP because I detected at rabbit at 50 yards that I thought might be a hog at 250 yards is a prime sort of example, embarrassing as it may be. So too comes the problems of identifications of targets at distances that are often nothing more than white or black silhouettes without much detail. So distinguishing between a coyote, fox, and similar domestic dog can be problematic. For many animals, you have to look at their behavior and locomotion. Deer with their heads down can look a lot like hogs, especially when their feet are hidden by the grass and you can't really tell how long their legs are. A possible hog that raises its head and has a long neck can magically turn into deer. The point here is just to reiterate the problems in the terminology of detection, recognition, and identification. There are a lot of things you can detect at long distances, but then never have a clue as to what they are unless you are able to approach them. I have undoubtedly detected all of the above animals at longer distances, but never knew what I was seeing, hence can't tell you that I saw them.
Sorry, Ben, that was probably way too much more answer than you wanted. I had not given this a lot of specific thought before replying, so you are getting my stream of (un)consciousness.
