[Mistral75]

(...)

Canon, on the other hand, ditched their FD mount in favor of the all-electronic EF mount when they started introducing autofocus in their film SLRs. The new mount's wider diameter and shorter flange distance, in addition to its different bayonet mount, required an adapter for FD lenses to work on the then-new EF bodies.

Wider diameter, yes: 54mm for the EF mount vs. 48mm for the FD mount.

Shorter flange distance, no: 44mm for the EF mount vs. 42mm for the FD mount.

This is the reason why Canon only proposed a 4-element optical adapter which acted as a low power multiplier (1.26x) for FD telephoto lenses and no conventional adapter without glass, with which the flange of the FD lens would have to be 2mm inside the EOS body.

The 1.26x FD -> EOS adapter had a protruding front element (similar to the current Canon teleconverters), which meant it would only couple with lenses which could accommodate this protrusion.

[Breakfastographer]

Strangely, Nikon offers full backward compatibility on the dF and significant backward compatibility for all AIS back to the mid-1970s on their upper tier models. Even stranger...they still sell some of those manual focus lenses.

When Nikon introduced autofocus, they did so with their existing F mount. They've added electronic connections, but the physical mount has remained the same since 1958, making compatibility easier to maintain. Nikon only moved to a new mount with their Z-series mirrorless cameras.

Canon, on the other hand, ditched their FD mount in favor of the all-electronic EF mount when they started introducing autofocus in their film SLRs. The new mount's wider diameter and shorter flange distance, in addition to its different bayonet mount, required an adapter for FD lenses to work on the then-new EF bodies.

My point was that Nikon offered (and continues to offer) full backward capability to 1958 on the Df even though such had been absent from the line for a long time. Part of the reason why there is such complaint here regarding the crippled mount is that the mechanism is actually very compact and incredibly simply and there is no clear rational why it was removed. Users might be happier if stop-down metering worked better, but it remains a cludge.

The Df is definitely the one to watch - starting at a high price and holding it, yet a very slow burner in the market. If it weren't for the now-low resolution, perhaps it would still be available new. It certainly did the thing it set out to do, with the occasional gremlin along the way.

I think a K-1 III with extra backwards compatibility would be very interesting. It seems to me to make the most sense for a full frame body, to be able to use the legacy lenses at their original focal lengths.

[stevebrot]

If it weren't for the now-low resolution, perhaps it would still be available new.

Surprise! It is current Nikon product. 16Mpx sounds low, but consider that the D6 only supports 20Mpx, the Df aligns nicely. I know a couple of people that bought a Df new and they aren't selling.


Steve

[mlt]

As nice as it would be to use my M series primes with full aperture metering control, I don’t see Ricoh changing their mind about altering the current K mount to fully support 35-45 year old lenses. Since I’m manually focusing then anyway, the green button method of metering isn’t that much of a bother.

[ecostigny]

Wider diameter, yes: 54mm for the EF mount vs. 48mm for the FD mount.

Shorter flange distance, no: 44mm for the EF mount vs. 42mm for the FD mount.

This is the reason why Canon only proposed a 4-element optical adapter which acted as a low power multiplier (1.26x) for FD telephoto lenses and no conventional adapter without glass, with which the flange of the FD lens would have to be 2mm inside the EOS body.

The 1.26x FD -> EOS adapter had a protruding front element (similar to the current Canon teleconverters), which meant it would only couple with lenses which could accommodate this protrusion.

My mistake regarding my assumption that the flange distance would be shorter with a wider diameter; I should have dug a bit further into the mount specifications that night. I can see how this difference would make the design of adapters that much more challenging.

[Mistral75]

My mistake regarding my assumption that the flange distance would be shorter with a wider diameter; I should have dug a bit further into the mount specifications that night. I can see how this difference would make the design of adapters that much more challenging.

When SLR manufacturers launched a new mount to add autofocus capability, the trend was to increase both the diameter (ø) and the flange focal distance (FFD):

• Canon FD (ø = 48mm ; FFD = 42mm) --> Canon EF (ø = 54mm ; FFD = 44mm)
• Contax/Yashica (ø = 48mm ; FFD = 45.5mm) --> Contax N (ø = 55mm ; FFD = 48mm)
• Minolta SR (ø = 45mm ; FFD = 43.5mm) --> Minolta AF (ø = 49.7mm ; FFD = 44.5mm)

[MMVIII]

When SLR manufacturers launched a new mount to add autofocus capability, the trend was to increase both the diameter (ø) and the flange focal distance (FFD):

• Canon FD (ø = 48mm ; FFD = 42mm) --> Canon EF (ø = 54mm ; FFD = 44mm)
• Contax/Yashica (ø = 48mm ; FFD = 45.5mm) --> Contax N (ø = 55mm ; FFD = 48mm)
• Minolta SR (ø = 45mm ; FFD = 43.5mm) --> Minolta AF (ø = 49.7mm ; FFD = 44.5mm)

Interesting, was it to accommodate the room for an adapter to make the transition for existing users less painful or was there an optical-technical rational behind it?

[Zygonyx]

f/1.4 rational ?

[Mistral75]

Interesting, was it to accommodate the room for an adapter to make the transition for existing users less painful or was there an optical-technical rational behind it?

If it had been to accommodate the room for an adapter, the newer mounts would have had a shorter flange focal distance, not a longer one which made impossible to design glassless adapters to use the older lenses on the newer bodies.

The reasons were therefore optical-technical for the larger diameter and technical too for the (slightly) longer flange focal distance.

Asahi Optical have been the only one to keep the same flange focal distance for their three successive lens mounts.

[MMVIII]

If it had been to accommodate the room for an adapter, the newer mounts would have had a shorter flange focal distance, not a longer one which made impossible to design glassless adapters to use the older lenses on the newer bodies.

The reasons were therefore optical-technical for the larger diameter and technical too for the (slightly) longer flange focal distance.

Asahi Optical have been the only one to keep the same flange focal distance for their three successive lens mounts.

Oh, wow. Sure, you are absolutely right. I had it the other way around, my bad. Backwards compatibility of new lenses to old mount-cameras probably really is not a real factor...

[ecostigny]

Oh, wow. Sure, you are absolutely right. I had it the other way around, my bad. Backwards compatibility of new lenses to old mount-cameras probably really is not a real factor...

The relative lack of focus on backwards compatibility didn't seem to hurt Canon too badly; they claimed to have sold more than 100 million EF mount lenses six years ago. To a manufacturer, a new lens mount is a great excuse to promote buying new glass, especially if that new glass has hitherto-unavailable capabilities like autofocus.

[thibs]

The relative lack of focus on backwards compatibility didn't seem to hurt Canon too badly; they claimed to have sold more than 100 million EF mount lenses six years ago. To a manufacturer, a new lens mount is a great excuse to promote buying new glass, especially if that new glass has hitherto-unavailable capabilities like autofocus.

At the time it did cost them a lot.
A lot of people, still now, will refuse to buy Canon because of that (the mount and the circumstances at the time).

It didn't prevent Canon from gaining a lot of other sales for other reasons (technical being one of them).I don't think Minolta suffered that much although they did change the mount too.