Yeah I know there's another thread that kind of talks about this, but it's six pages of speculation on whether or not there would even be a new mount.
Now that we know for sure that there's a new mount, I started to consider what I wanted to do with all of my EF lenses since I do plan to buy into the new RF camera system. After a lot of consideration, I think I've realized that this whole issue is a lot simpler and more trivial than we all seem to be making it out to be.
For the sake of the argument of what happens to EF lenses now that there's an RF mount, I think the first thing that needs to be established and accepted is that an EF lens adapted to an RF body will give you performance just as good as that EF lens on an EF body. Canon themselves likely knows this, and everything I've seen with regard to the performance of the EF to EF-M adapter seems to support that a Canon adapter adapting a Canon lens onto a Canon camera will have no hiccups in regard to performance.
So if we accept that using the adapter is essentially a non-issue and shouldn't be shied away from, that means that in effect, any EF lens can be made into an RF lens, and any RF body can be made into an EF body just by putting an adapter on it.
Since you can still make any of your current lenses work with any new body that comes out now or into the future, they will effectively never truly be out of date from a compatibility standpoint. And at that point, the question of "should I ditch all of my EF glass as new RF lenses come out?" really becomes more of a question of "would I ditch this EF lens if Canon came out with a better EF sequel to this lens?" We need to stop looking at EF lenses as relics that will be hopelessly out of date within a few years, because they won't, they'll work on EOS R cameras well into the future.
Take the new RF 50mm 1.2 for example... If you stuck an adapter on the back of an EF 50mm 1.2 to make it an RF lens, is there really any reason that you couldn't just consider the EF 50mm 1.2 to be an RF 50mm 1.2 version I, and the actual RF 50mm 1.2 to be version II of the same lens?
So if you're stressing out about whether to sell your EF 50mm 1.2 for an RF 50mm 1.2, how is that conflict really any different than asking yourself if you would get rid of the EF 50mm 1.2 if they came out with an EF 50mm 1.2 version II? (Assuming you're going to buy an RF camera that can use lenses of either mount.)
They'll both work fine on your camera, but do you want to pony up for the new lens, or keep using the old one?
Ultimately I think there's a strong case to be made that Canon will never phase out the EF mount, because honestly what do they gain by making a new lens in the RF mount? The diameter is the same, you get a shorter lens to sensor distance, and ok, you get a couple extra electrical contacts, but that's it. And I think we can see from looking at the long telephoto lenses that those lenses really don't benefit from it since the rear element is already deep within the lens anyway. So why would Canon ever bother with moving these lenses over to the RF mount natively when you can just throw an adapter on them and make them an RF lens?
I think you can see from the RF lenses they've already announced that they're using the shorter distance of the RF mount to make lenses that just physically wouldn't have been possible with the EF mount. The 28-70 f2 probably wasn't possible with EF, and the 50mm 1.2 with that advanced of an optical formula probably wasn't possible with EF, or at least it's optimized to take advantage of the shorter sensor distance.
But when it comes to lenses that really don't benefit from the shorter distance, I could see Canon just leaving them as EF lenses forever. Want to use it on mirrorless? Get an adapter. It'll work flawlessly. Want to keep using it on your DSLR? No problem.
If we back up and really look at how minor the differences are in the mounts, I think it's clear that in a lot of cases Canon simply doesn't have a huge incentive to ever change a lot of the lenses over to RF, unless their optical performance can actually benefit from the shorter distance.
Now that we know for sure that there's a new mount, I started to consider what I wanted to do with all of my EF lenses since I do plan to buy into the new RF camera system. After a lot of consideration, I think I've realized that this whole issue is a lot simpler and more trivial than we all seem to be making it out to be.
For the sake of the argument of what happens to EF lenses now that there's an RF mount, I think the first thing that needs to be established and accepted is that an EF lens adapted to an RF body will give you performance just as good as that EF lens on an EF body. Canon themselves likely knows this, and everything I've seen with regard to the performance of the EF to EF-M adapter seems to support that a Canon adapter adapting a Canon lens onto a Canon camera will have no hiccups in regard to performance.
So if we accept that using the adapter is essentially a non-issue and shouldn't be shied away from, that means that in effect, any EF lens can be made into an RF lens, and any RF body can be made into an EF body just by putting an adapter on it.
Since you can still make any of your current lenses work with any new body that comes out now or into the future, they will effectively never truly be out of date from a compatibility standpoint. And at that point, the question of "should I ditch all of my EF glass as new RF lenses come out?" really becomes more of a question of "would I ditch this EF lens if Canon came out with a better EF sequel to this lens?" We need to stop looking at EF lenses as relics that will be hopelessly out of date within a few years, because they won't, they'll work on EOS R cameras well into the future.
Take the new RF 50mm 1.2 for example... If you stuck an adapter on the back of an EF 50mm 1.2 to make it an RF lens, is there really any reason that you couldn't just consider the EF 50mm 1.2 to be an RF 50mm 1.2 version I, and the actual RF 50mm 1.2 to be version II of the same lens?
So if you're stressing out about whether to sell your EF 50mm 1.2 for an RF 50mm 1.2, how is that conflict really any different than asking yourself if you would get rid of the EF 50mm 1.2 if they came out with an EF 50mm 1.2 version II? (Assuming you're going to buy an RF camera that can use lenses of either mount.)
They'll both work fine on your camera, but do you want to pony up for the new lens, or keep using the old one?
Ultimately I think there's a strong case to be made that Canon will never phase out the EF mount, because honestly what do they gain by making a new lens in the RF mount? The diameter is the same, you get a shorter lens to sensor distance, and ok, you get a couple extra electrical contacts, but that's it. And I think we can see from looking at the long telephoto lenses that those lenses really don't benefit from it since the rear element is already deep within the lens anyway. So why would Canon ever bother with moving these lenses over to the RF mount natively when you can just throw an adapter on them and make them an RF lens?
I think you can see from the RF lenses they've already announced that they're using the shorter distance of the RF mount to make lenses that just physically wouldn't have been possible with the EF mount. The 28-70 f2 probably wasn't possible with EF, and the 50mm 1.2 with that advanced of an optical formula probably wasn't possible with EF, or at least it's optimized to take advantage of the shorter sensor distance.
But when it comes to lenses that really don't benefit from the shorter distance, I could see Canon just leaving them as EF lenses forever. Want to use it on mirrorless? Get an adapter. It'll work flawlessly. Want to keep using it on your DSLR? No problem.
If we back up and really look at how minor the differences are in the mounts, I think it's clear that in a lot of cases Canon simply doesn't have a huge incentive to ever change a lot of the lenses over to RF, unless their optical performance can actually benefit from the shorter distance.