I'm going to try to be a little more complete about that, because it's not quite that simple. And all this refers only to F mount cameras, in case that's not obvious - lest anyone stumble in here with a Canon body and be confused. When the aperture is controlled by the lens's aperture ring, I believe DoF (and probably live view, though I didn't check) will work on all bodies. It certainly does on my F5 and D810. In this case, the DoF preview button, like the shutter release, simply drops the aperture coupling lever on the camera to its maximum extent, and lets the aperture stop-down lever run free; its motion is stopped by the aperture ring on the lens. I assume this is true even for cameras with no meter coupling lever around the mount. With the exception of the EE control units (DS-1, DS-2, DS-12), no camera has control over the aperture when the lens is used like this - so you mostly can't use P or S modes in this case. For reasons I'm not entirely clear on but which may relate to the aperture mechanism, no DSLR supports stop-down metering, even in spot metering mode (which, unlike matrix metering, should still work when the lens isn't wide open). Electronic lenses with aperture rings "just work" when the camera has an aperture coupling lever, otherwise the camera insists on control and requires minimum aperture unless you lie to it by wedging the EE button. Lenses with no electronic connection always work like this on a dSLR - although as I've said before, I see no mechanical reason why an AI-S lens should not have its aperture controlled by a modern dSLR body; only a few film bodies, including the FA and F501, support aperture control by moving the aperture lever with non-electronic lenses. G lenses have no meter coupling ridge or aperture ring, and so the aperture has to be controlled by the camera. When the aperture is controlled by the amount of motion of the aperture coupling lever (whether by being in P or S mode, or controlling the aperture manually from the body controls), most cameras seem to have a separate control over the amount the aperture lever moves and actuating its movement - in some cases, this seems to be hooked to the mirror motion, which I believe is why the D700 flips its mirror before a shot even in live view. I can't speak for the FA (which has a weird active feedback system), but I believe this is true of the F5, and I suspect also cameras like the F4, F100 and F6. The effect of this is that when you press DoF preview and then adjust the aperture from the camera, nothing appears to happen; likewise in live view, or when shooting video. To change the aperture you need to reset the system by releasing DoF preview, or exiting live view/video (or taking a shot, in some cases). With the D8x0 series (at least, I hope for the D850), the D3, D4 and D5 ranges, the D750 and D500 (I believe), the camera can dynamically move the aperture coupling lever. This means that aperture changes during DoF preview take effect immediately, and the same applies to live view and video - and this is how "power aperture" mode works for video. The camera will also adjust the position of the aperture lever as you move a variable aperture zoom to maintain the requested aperture (where possible), which doesn't happen with a D700 (I tried it when I had a D700 and D800 concurrently). In shutter priority mode (and I had to try this because I almost never shoot in S), the camera will adjust the aperture in DoF preview while you modify the shutter speed. At least on the D810, this doesn't seem to apply to P mode - the stated aperture in the finder changes, but the aperture lever doesn't move, for some reason. I'm less clear on how well metering works while stopped down - conventional matrix metering compensates for the fall-off of the lens, and doesn't like being used except wide open. When the lens has an E aperture, the aperture is communicated electronically and the movement of the aperture coupling lever is irrelevant. I see no mechanical reason why any Nikon camera that supports E aperture lenses should not be able to move the aperture dynamically in the same way that the high-end bodies can control lenses with their aperture coupling levers. However, I have neither an E lens nor a camera that doesn't support power aperture with which to try it. Can anyone report back? Nikon aren't terribly forthcoming about this in their documentation. I hope that's more complete; I'll be interested to know about the E lens situation. Not that this helps Ian much.