I just joined the forum today. I have a new Canon R5 and a couple of starter lenses to get me going. Very excited to get back into photography now that I have some time for it and found the Canon forum interesting.
Is there a source of information about the electrical interface and control protocol of the RF mount camera interface? I am familiar with the EF mount interface. Is this a good forum to discuss this? I enjoy hacking electronic things but before spending lots of time on this I wondered if others have gone down this path before me so I can have a better foundation.
It appears to be EF reverse compatible if an adapter is used so are the 8 original pins basically the same and just 4 "RF" pins added?
I am afraid there's not much (if any) public knowledge on this, and furthermore this is not a forum frequented by folks who are into that much technical detail. People here argue more about the merits of one feature over another, and the look of one particular lens over another
Thanks for the response. Well, since I'm a lens/camera consumer too, this forum will certainly help feed that aspect of my hobby.
I've spent months on projects like this to then uncover that the information is already well defined. Just looking to avoid repeated work and to avoid destroying anything expensive in the process. Googling has its limitations in finding some of the more gritty technical information out there.
a) there must be some straight through pins on the mount for EF lenses to be adapted. That there are low cost third party adapters would suggest there isn't any protocol conversion, though maybe it's something easily deciphered.
b) there's significant information going to and from an RF lens:
According to above link, there is gyro/accelerator data and DLO information. There's also firmware updates, but that was in EF lenses previously.
If you were designing that, on the extra four pins, presumably you'd want extra headroom for any future communication needs. So that would suggest something much faster than the SPI interfaces on EF lenses.
I suppose if this was the kind of thing you were into, you could put a scope w/protocol analyzer on those pins and take a look. But I think we're far too early in the RF mount to have this sort of experimentation well known yet and Canon very likely will not be publicizing this to reduce third party lens advantages.
Thanks for the post and the link. I do plan to put analyzers / scopes on the lens/camera.
I had some guesses too but they need to be checked out.
My first guess was that the original 8 "EF" pins are the same for backwards compatibility.
My second guess is that the camera starts communicating in backwards compatible "EF" protocol / speed, IDs the lens and then conditionally switches to "RF" protocol/speed and only then conditionally uses the extra 4 pins.
Time will tell. I just purchased a cheap RF lens extender that I hope just passes through all 12 pins. I can possibly tear that down to add a connector for sniffing the signals. Should be fun.
RF_780 wrote:
Thanks for the post and the link. I do plan to put analyzers / scopes on the lens/camera.
I had some guesses too but they need to be checked out.
My first guess was that the original 8 "EF" pins are the same for backwards compatibility.
My second guess is that the camera starts communicating in backwards compatible "EF" protocol / speed, IDs the lens and then conditionally switches to "RF" protocol/speed and only then conditionally uses the extra 4 pins.
Time will tell. I just purchased a cheap RF lens extender that I hope just passes through all 12 pins. I can possibly tear that down to add a connector for sniffing the signals. Should be fun....Show more →
You can google it and some basic diagram and info will come out as the pin out and other stuff
tsangc wrote:
a) there must be some straight through pins on the mount for EF lenses to be adapted. That there are low cost third party adapters would suggest there isn't any protocol conversion, though maybe it's something easily deciphered..
I don't think this is a correct assumption. It is quite likely that R bodies simply speak both "EF and RF languages" and while the adapters are indeed dumb, it doesn't mean that the EF and RF protocols are the same, or that some pins are dedicated to be pass thru.
As an example, both Thunderbolt 3 and USB-C (and USB4) use the exact same connector, and some cables are universal, but they're decidedly different protocols, and no pins are reserved as "passthrough" of the older protocol.
No you guys are right, there very well could be a sense detect sequence on the legacy pins that an RF body knocks on the door of an RF lens to enable a different mode.
You'd really need several EF and RF lenses to be sure of all the intricacies.
Depending on your goal, another way about it may be to control through an alternate firmware. Like if your goal was to automate focusing for some sort of time lapse or bracketing project, you could potentially script inside Magic Lantern and force focus touches. That way you drive the lens through the whole hardware and software stack, abstracting RF/EF etc away.
Note Magic Lantern probably hasn't been ported to R bodies yet.
I suppose it's a question of how big is the itch you want to scratch.
So my plan so far, if you can call it a plan, is to just investigate the new interface. I don't have any specific goal in mind except for the hunt itself.
If anyone wants to buy some RF lenses for me to test, maybe one of each... That would be helpful.
