Discontinued Canon EOS Film Bodies

The EOS-1n is the second generation of EOS professional bodies (following the EOS-1), now replaced by the third generation EOS-1v. It has 5 focus zones (the EOS-1 had only one), speeds to 1/8000, 1/250 flash sync and true mirror lockup (the EOS-1 had no mirror lockup). Nice features are a seperate button for DOF preview, a built in eyepiece blind and built in adjustable diopter correction for the viewfinder. It has a PC connector for studio flash use (missing from Elan and Rebel models). The EOS-1n ia a fine camera body, very rugged, fairly weather resistant (OK in rain but don't dunk it!) and generally reliable.

One thing that might not be obvious to many people is that only the center focus zone has a cross sensor, and it's only a cross with lenses of f2.8 and faster. With slower lenses it only focuses on detail in one plane. The Elan II, for example, has a center cross sensor which is active as a cross with all lenses f5.6 and faster. The upside of the EOS-1n is that focus is more accurate with fast lenses. The downside is that AF may not be quite so positive with slower lenses.

The Elan II has most of the features of the Elan (except for the zoom function of the built in flash), plus many more. It has 3 focus zones, support for FEL (flash exposure lock) and high speed sync (to 1/4000s) with EX series speedlites. Flash sync with "normal" speedlites is 1/125. An analog metering scale is available in manual mode. A battery pack (BP-50) which takes 4xAA cells is available (very useful, especially when used with rechargeable NiMH cells).

The Elan was the first "consumer" body with the rear control dial. This is a big plus. You can adjust exposure compensation in auto modes, and set aperture/shutter speeds in manual mode without having to push buttons and take the camera from your eye. Shutter speeds from 30 to 1/4000s are provided and flash sync is 1/125s. There is no analog metering scale in manual mode, just over/under indications. The Elan has only one focus zone. The built in flash has a zoom head. Perhaps the Elan's main "claim to fame" is that it may be the quietest EOS body. It's not silent, but it is pretty quiet. A nice camera, but significantly improved in the Elan II.

The EOS 10s was the first EOS body with multiple (3) AF zones. It also had a number of unique features such as a built in intervalometer for doing time sequence shots. A very nice camera, lacking the rear control dial introduced on the EOS-1 and later on the Elan (the first "consumer" body with this feature). Unless you really need a built in intervalometer though, I think the Elan (or Elan II) is probably a better buy if you're considering a used EOS body.

The Rebel and Rebel S were the early versions of the Rebel II and Rebel II S. They are pretty much identical, but the earlier versions only have a 1/1000 second top speed and lack the "musical" self timer and "soft focus" features of the IIs. The "S" versions have built in flash. The original Rebel does, however have an analog metering display in the viewfinder, a very useful feature shared only with the EOS ElanII and newer models in the US! For this reason alone some people might prefer the Rebel to the Rebel II. All the Rebels have a plastic lens mount. Some people don't like this idea much, but in practice it does not seem to be a real problem, provided you don't do a lot of lens swapping. Note that all the other EOS cameras have metal lens mounts, so if it really worries you then consider the other models. The Rebel is very light, so if that's really important to you, it might be a good buy. It uses a 2CR5 lithium battery unlike some later Rebel models. This might be a concern if you're using it as a backup (carrying only one type of battery is a plus!).

The EOS RT was introduced in December 1989. It was the first modern AF SLR camera with a fixed mirror (pellicle) system and as such was unique. A fixed mirror version of the EOS-1n (rs) was introduced later. The fixed mirror system means that you get no viewfinder blackout, and in the RT mode the shutter delay is only a few milliseconds. The delay of a typical SLR is about 1/8 second (125 milliseconds), so for "action" work you have to anticipate. Other than the fixed mirror it is very similar to the 630, with a few more custom functions and no PIC exposure modes. If you want a pellicle mirror camera, this is the only one you'll find under $500!

The EOS 630 was introduced in March 1989 and has now been "replaced" by the Elan and is no longer in production. It is still a very good camera with features absent from most of the current EOS line. In some ways it is closer to the EOS 1 than to either the 10s or the Elan. It has interchangeable viewing screens, an illuminated LCD display. It can take data backs, including the technical back E (TBE). The TBE has full data recording and control over the camera functions. The 630 is the most advanced body compatible with the TBE, so if you want a TBE the 630 is the best body to use with it.  The 630 has a wired remote control which does not self cancel (like the 10s and Elan do). It has an all-metal "sub frame" with metal film rails. It has all the exposure modes of the current EOS cameras (program, depth, Av, Tv, Manual, PIC). The 630 is not as well designed ergonomically as the later EOS cameras. To do much manual metering takes a lot of inconvenient "button pushing". To change modes needs two hands etc. Overall it is a good buy if you can live with the buttons! It does not have any kind of mirror lock up, or mirror prefire capability nor does it have a built in flash. 
 

I haven't personally used any of the following older EOS bodies, but I'm including some historical information for reference purposes.

The EOS 700 was introduced in March 1990 and discontinued in September 1990. That may tell you something. It is sort of a slightly upgraded 750. It has built in flash. Exposure modes are program, depth, shutter priority and PIC. Film speed is DX coded with no manual override. The 700 also "prewinds" the film like the 750/850/Rebel. 

The EOS 750/850 are very simple "entry level" cameras, introduced in September 1988 and discontinued in 1990. They have no manual settings. Exposure is "program" or "depth" and film speed is DX set with no manual override. The cameras are identical except that the 750 has a built in flash. Neither is a particularly desirable camera. Think of them as P∓S cameras with interchangeable lenses. Both cameras "prewind" the film like the Rebel. 

The EOS 620/650 were earlier "versions" of the 630, with less features, a slower CPU (slower AF) and slower film transport (3fps vs 5 fps). As such they are not particularly desirable. They were introduced in February 1987 and discontinued in 1990. The 650 is the more basic model, lacking the multiple exposure capability, auto exposure bracketing and an illuminated LCD display of the 620. The 620 also has the desirable feature of flash sync at 1/250. The only other camera in the EOS line with 1/250 flash sync is the EOS-1, so if you need it a 620 could be a good buy. The EOS 650 syncs at 1/125, like the 630. If you don't need the 1/250 sync speed, the 630 is a much better buy than the 620, more features, faster AF. The 620 also has a 1/4000 top speed, whereas the 650 (and 630) both top out at 1/2000. Both the 620 and 650 have intelligent program, Tv, Av and manual exposure modes, but no PIC modes (like the 630 has). The 650 also has the "depth of field" mode which is lacking in the 620, the only case where the 650 has a feature not present in the 620. There could be good reasons to buy a 620 (if shutter and sync speed are important to you), but I can't think of a reason to buy a 650 unless it was really cheap.