But, from auto into manual, using exposure lightens or darkens from where you left auto. Period. If auto gives the correct exposure ("picture quality"), going + or - makes exposure wrong.
First part I agree with But going + or minus does not make it wrong, it just makes it closer to what YOU consider right! ( recall I like my peak white to be shifted down to 95 IRE ) exposure and iris always work in tandem when one or the other is in auto. In this case exposure in manual then auto will attempt to track the manual setting until it reaches the maximum or minimum opening. If both could be set to manual, ( 2D ) then there would be no tracking of the iris.
I still say you are not seeing the big picture on how these controls work. They work just like they should and the results are predictable. As I said, the only strange thing I see is the location of A.E. being on the knob. In my opinion it could have been left to the buried menus. But that doesn't affect what it does or how it works. AE is just a calibration tool, not a way to adjust manually for shooting.
On my broadcast cameras, you know I have two of these settings. One is located on the camera and the second is located on the lens. But, you would always leave one in default and only calibrate with the other. If you have 2 or more lenses then you set the camera for zero and calibrate each lens. If you use just one lens then you would calibrate the camera and leave the lens alone. It is usually more difficult to calibrate the AE on a lens than on the camera. Back Flange calibration is always done on the lens as it sets the back lens element the proper distance from the first optical element in the camera. Fixed lenses do not require this calibration. If you ever went through this calibration process on a broadcast camera you could see the f-stop actually track the AE on the servo. All this is hidden from view on consumer camcorders.
As for the manual not being very good, I agree but I wouldn't expect the manual on a camera to explain basic photography. Sony is not changing the definitions of what these controls do, but they also don't explain why some are disabled in 3D. I understand why you set AE in 2D only and then it is "locked" in 3D. That is simple physics! But I can only guess why you don't get manual shutter speeds in 3D and you do in 2D. My guess is cost. The circuitry to track the shutter speeds on two cameras had to be sacrificed, considering consumers probably would rarely use that.
The NEX cams allow for the extra shutter speed, 24P. That's it for 3D. I believe there are two versions of the pro cam just as in the consumer that permit the 50i and 25P in 3D but both are available in 2D. ( Going from memory on that one)
Very important for you to understand: Your assumption that AE shift doesn't exist in 3D is wrong. Sorry, but the fact is it is "locked" to what ever you set it at in 2D. If you feel you are not getting the correct exposure the way the camera was factory calibrated. over ride that with AE in 2D and then, leave it on. switch to 3D and the new calibration will hold in locked position. If you connected a WFM to the TD10 composite output and put the camera on a gray scale test chart you would see that the new AE calibration holds.
I believe the minimum distance in maximum telephoto for focus is closer than 25ft. But I can't say I ever measured it. I would have said 10 ft.
This assumes smallest aperture, brightest lighting.
I don't own that many consumer camcorders but I can tell you that all I have said holds true for both my HDR SR12 and the TD10. Just for the TD10 some things are unnecessary or disabled. The AE works exactly the same way the exposure works the same way and iris the same way. Neither camcorder offers ND filters. The last small camcorder I have with internal ND filter (2 of them) is the PD100 but this is considered a professional series, similar to what the NEXcam series is sold under. The AE exposure auto iris etc all work the same in this much older vintage camcorder. I'd say the way all these controls work is consistent over the last decade!
DOF is a viable creative tool, not just for academics. But it is far more difficult to operate in these consumer camcorders than the pro rigs. The last small camera I used that could be easily used for racking a focus was the HVR Z1U. In fact there was a "focus puller" that could be attached just for that purpose. You could set the camera up then measure your distances between points of focus. start shooting and pull a lever arm as you racked the focus ring through the shot. It wasn't a cheap accessory.