This really isn't about the camera so much, but rather about the lens. None the less, I thought the F the best camera on which to play with the lens As most folks know, autofocus really started hitting heavily in the 1980s, with active systems(either IR or ultrasonic) showing up P&S and Polaroids early in the decades and passive focusing making its way into SLRs by the late 1980s. Like most things, both systems have their advantages and disadvantages, but ultimately passive AF won out and-to my knowledge-all current production AF cameras either use a phase detect or contrast detect passive system. In any case, AF came last to SLRs. For Nikon users, it arrived in the F3 AF in 1983, N2020(or F-501 to anyone outside the US) in 1986, and in the professional F4 in 1988. All of course used a passive phase detect system. The N2020 and F4 both primarily used the in-body motors coupled to the lens, while the F3AF used in-lens motors. The F4 could also operate F3AF lenses(both of them) and the extremely expensive AF-I lenses(super-teles with integrated focusing motors). The latter became significant about 10 years later when Nikon started moving virtually all their lenses to in-lens motors, and the F4 continued to be able to operate them. There were, however, solutions for folks already invested in manual focus bodies, and this is one of them. Vivitar released at least one lens(maybe a couple) with an integral phase detect AF system and focus motor. The example I have is a 28-70mm zoom lens. It is powered by 3 AAA cells located in the side of the lens barrel. Here is the beast mount on an F. Just to keep things interesting, this is the oldest F I own-a 6.4 million SN body from about 1961. I bought it both for the serial number and the presumably original 5.8cm f/1.4 it came with, although unfortunately the body was "hacked" later in life to accept the FTN finder(this is something any buyer of an early F needs to look for, and of course adjust the price accordingly). In any case, the lens is fully compatible with this body-although it's difficult to see, this is an AI-s type lens with with a metering fork installed. As such, it is fully compatible with any camera that can work with non-CPU lenses. I can't find a lot about the lens and I'm not sure who made it for Vivitar. The optics seem decent for a 1980s zoom, and given that this was likely an expensive lens when new I suspect that they used Kiron or one of the other better makers. The AF is not TTL, but rather works via the large sensor off to the side. This is one of the failings of the lens in my view-it's impossible to tell just WHAT exactly you're focusing on. When I was playing with it while taking the photos, I put the split-image on a chest of drawers across the room and hit the button. When the lens beeped, the drawer wasn't in focus-instead it had decided to focus on a closer light stand. In any case, operation is a straight-forward if a bit slow. The aperture ring works like any Nikon lens, and zooming is via a tab on the underside. There are two switches on the top of the barrel. One is marked ON and OFF/MACRO. The "on" position is, of course, self explanatory. The "off" position allows the zoom ring to be moved into the "macro" position for closer(manual) focusing. I can't see any way to disengage the motor and gears, so manual focus presumably should ALWAYS sound like you're fighting the gear train. The lens also has a switch marked "S" and "C" for single and continuous AF. Once the lens is on, AF is started by pressing the large button on the side. It does not exactly focus fast, and as a primitive phase detect system it needs a decent amount of light as well as some contrast. The lens will hunt a bit, but once it has achieved focus at least in "S" mode you will be rewarded with a typical 1980s electronic beep and the red light on the front of the lens flashing. There is also a PC socket on the side of the lens. From what little I've been able to dig up, it seems as though this can be used to start AF, although I'm not sure how exactly. To me, this was an interesting little $15 curiosity I tacked onto a KEH order. I have seen a few of these for sale. All that I've seen have been in F mount, although I suspect that other mounts are out there. The fact that they DO seem to turn up in F mount is interesting to me, though, as for other "hot" Vivitar lenses(like the 35-85 2.8 Varifocal that I love) the F mount version seems to be the most difficult to find. In any case, that's what I know about the lens, and I'd be interested in seeing any other information other folks may have.