Fotomacher Loc: Toronto

For quite some time I have been using and enjoying old Nikon F mount glass with a succession of Nikon digital bodies. For example, one of my gems is a Nikkor 35mm f/1.4 AIs which my D810 meters flawlessly. My 16mm fisheye is the AF f/2.8D version. Yesterday's pro lenses are great value for today's soon to be pros. Nikon has built in backwards compatibility. Has Canon done the same?

MT Shooter Loc: Montana

Nikon is well known for continuing to use the same bayonet mount for almost 60 years. Canon has intentionally obsoleted their mounts preventing such use. Even with today's EF and EFS mounts. These lens mounts are actually identical but Canon adds a plastic extension ring to their EFS lenses that comes into contact with a buttress added to their bodies intentionally preventing mating the lens to their full frame bodies.

cmcaroffino Loc: Sebring, FL

I have several of the Nikon AIS lens that I love using on my D7200 the AIS 20mm, 28mm 55micro what quality lens that are much smaller than today's current crop of lenses. That is the main reason I wouldn't get the D7500 because these lenses will no longer meter with the D7500l. I also have several current zooms for my D7200 but they don't give me the emotional feeling or enjoyment I get with my old ais lenses. The are just tools that get the job done. Canon chose not to go the route Nikon did when going to the new auto focus lenses and from a marketing viewpoint it was probably the right decision as Nikon lost a lot of professional photographer's business at that time and have never recovered from it.

BebuLamar

Canon is backward and forward compatible for the past 30 years. Before that none. But Nikon lenses in a way is compatible for the past 57 years but there are a lot non compatible and confusion along the way. My Nikon Df can use lenses dated back 1959 but it's not compatible with the new AF-P lenses.

rehess Loc: South Bend, Indiana, USA

These days everything is Canon vs Nikon. The lens kitted with the Pentax I purchased in 1984 works as well with a modern Pentax as it did with the 1984 Pentax. With the exception of a minor extra step needed in metering, lenses going back even further would also work. However, Pentax has now announced a new mount, KAF4 {one lens actually released so far}, and neither camera could control the aperture on it.

MT Shooter Loc: Montana

The only difference in the KAF4 mount from the KAF3 mount is electronic, not mechanical so it is fully compatible. The KAF4 lenses will offer electro-magnetic diaphragm control for faster, more accurate aperture settings.

BebuLamar

In my opinion the Canon has the most compatible lenses. The 1984 Pentax K mount lens is only 3 years older than the oldest Canon EF mount lens. The OP favorite AI-s lens is also about 3-4 years older. Even when I bought my first Nikon F2AS in 1977 and if I wanted to use a 1 year older Nikon Pre AI lens I had to do stop down metering. In 1984 when I tried out the Nikon FA it needed AI-s lenses and not the lenses I bought in 1977 to ensure correct aperture.

dandi Loc: near Seattle, WA

Me too. I bought 6 or 7 old Nikon Lenses over the last year or so, they are so inexpensive. Lately have been shooting only with these lenses. I even bought two NON-Ai lenses (50mm 1.4 and 105mm 2.5). They were so cheap that I decided to try to convert then myself into ai, now they work fine on my D700/D7000. I would not say they are better optically then today’s AP-S lenses but they are fun to use.

rehess Loc: South Bend, Indiana, USA

I agree that KAF4 is a step forward - but the camera body needs to have the needed software. Pentax has released firmware upgrades for various cameras, including the K-50, but not for my seemingly virtually identical K-30 {although someone at the Pentax Forum did hack the K-50 upgrade to make a K-30 variant}. Of course, I would have no reason to expect my Super Program, the still-working one I purchased in 1984, to have been constructed with this kind of thing in mind.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

It's a somewhat confusing story to do with lens mount design and flange focus registration distances, complicated by digital camera technology, sensor size, form factor, and stabilization design.


Flange distance: This may be a place to start: http://briansmith.com/flange-focal-distance-guide/ Essentially any lens with with a flange distance less than that of the camera will not focus to infinity.

Canon manual focus SLRs (pre-1987) and FL,FD,FDn lenses had a flange distance of 42mm. With the introduction of the EOS system Canon increased that to 44mm so the older FD type lenses do not work easily. It can be done in some instances, but it is less than ideal or easy. However any lens for a camera with a flange distance greater than 44mm can be used with a simple adapter, which includes Nikon (46.5mm), Contax C/Y (45.5), Olumpus OM (46mm), M42 (45.46mm) and so on.

It is possible to use Canon FL/FD/FDn lenses on modern (post 1987) EOS cameras in two ways to achieve infinity focus. One is to have an adapter with a corrective lens element - these are of varying quality and may reduce the IQ of the original lens in various ways, or to replace the mount on the lens. This latter method is non trivial, is lens specific, and may cause mirror contact issues with full frame Canon DSLRs. On the other hand, using Nikon lenses of a Canon DSLR is a breeze.

Nikon advocates frequently claim superiority over Canon since any nikon lens can be mounted on a Nikon DSLR and achive infinity focus without loss of IQ since Nikon has not changed the focal registration distance. However, many of those lenses - especially autofocus lenses - may not function properly on all Nikon bodies, so it becomes lens / camera combination specific, even today. By comparison Canon made a bold move and obsoleted its older systems (30 years ago folks), but since 1987, any Canon EF lens will function on any Canon EOS camera - I will address EF-S and EF-M below. It is arguable that Canon's decision to make that bold change propelled Canon to a market leadership position that cannot be equalled by Nikon, Sony or any other vendor. It is the cleanest system design on the market bar none.

There are however, other complications, namely digital camera technology, sensor size, form factor, and stabilization design.

Digital camera technology and sensor size: Along with digital cameras came a shift away from 35mm film standards to a wide range of sensor sizes, which allowed for more variation in camera design, in particular allowing for smaller and lighter cameras which could also use smaller and cheaper lenses than their 35mm full frame brethren. Although Canon now has two sub-designs of the EF mount - one for APS-C DSLRs and a newer one for mirror less EOS cameras, they are just variants of the EF standard. EF-S lenses are smaller and less expensive, although many have very fine optics, but could cause mirror contact and vignetting issues on a FF camera. Hence the baffle that prevents them from being mounted - without modification - on FF EOS DSLR cameras.

Form Factor: Mirror less cameras typically have a smaller flange distance than DSLRs - no need for the mirror box, so adapters without additional optics are very practical which means that older Canon lenses (pre 1987) can be used without modification. As mirror less camera technology improves then older glass becomes even more viable, especially with Canon.

Stabilization design: There are two general approaches to stabilization - in lens or in body. Canon and Nikon (so far) use in lens stabilization, Pentax, Sony, and others use in body stabilization. In body stabilization has advantages for using older or non-stabilized lenses. As the move to electronic / mirror less cameras continues more vendors are likely to include in body stabilization technologies. Canon is already beginning to do this with its mirror less cameras (EOS M5 for example) although primarily for video so far.

The market is in transition, and will keep changing for many more years. As mirror less cameras become the dominant form factor it will become easier to use old glass.

By way of disclosure I am a long time Canon user, but have no particular bias against other vendors - I have my reasons, which may not apply to other people - however, the market is complicated now, so do not get led astray by anyone that has a strong vendor bias or gives overly simplistic explanations or opinions.

BebuLamar

Why I do understand the reason Nikon introduced the E lenses (electronic diaphragm) but I can't understand their introduction of the AF-P lenses which are not compatible to great number of current cameras.

rehess Loc: South Bend, Indiana, USA

First my full disclosure: I used Pentax 1979-95, then switched to Canon because I found their AF system to be superior to what Pentax and Nikon were doing. I switched back to Pentax in 2015 because I had issues with their bodies in my price range {namely Rebels}.

I am intrigued by the similarities between Nikon and Pentax users. Both seem to have one foot in the past; both are very suspicious of space-age plastics and both highly value lens mount compatibility {these thoughts are not very popular over at the Pentax Forum, incidentally}.

Personally, I enjoy using older lenses, but I don't really buy into the "lenses are forever theory". My observation is that each generation of lenses is superior to what preceded them, so if you can come up with funding, purchasing new lenses makes more sense than does using ancient ones. I enjoy using the various M42-mount and older K-mount lenses in my collection, but typically I use newer ones when IQ is most important to me.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

That seems like a very reasonable attitude. I enjoy using older manual focus lenses for some things, they are typically better than autofocus lenses for manual focus - different gearing and so on. However each has a place and purpose. It is complicated. I have a number of FL / FDn Canon lenses adapted for EOS cameras and they definitely have a place, but mostly I have the focal length ranges covered with modern autofocus Canon glass.

Alan1729 Loc: England UK, now New York State.

No Canon haven't done the same I had three FD bodies and more lenses than I could carry, then Canon brought out the EOS system and no adapter for FD lenses. That is when I jumped ship from Canon will never go back, I also try to persuade anyone looking to buy a new camera to buy anything other than Canon. I now use Micro 4/3, Olympus OMD M1 mk2 now, an amazing camera. I can use many of my FD lenses manual of course but mainly use the olympus Pro lenses.
Lots of other lens makers to choose from.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

Perhaps you should do your research a little more carefully. Canon did produce some adapters for FD to EOS. Not inexpensive, and not for every lens, but they did provide a transition path. You are clearly pissed off about that transition and the effect it had upon you, but not necessarily for accurate or good reasons. I had two Canon bodies (AE-1 and T90, still have in fact) plus multiple FD lenses, yet the transition didn't cause me to have negative feelings about Canon. They have done a much better job of compatibility over the last thirty years than most other vendors, and as they get more competitive with mirror less cameras such as the EOS M5 it gets much easier to use the older FD lenses. There are still ways of using FL/FD/FDn lenses on EOS cameras, especially the APS-C models, it's just a little more complicated.

Perhaps if you wish to bad mouth a vendor, it would help if you got facts correct first. As with Nikon, Olympus is not without any transition issues when using older lenses.