EF–R Pinout - will 3rd party lenses be locked out from RF mount?
I commented in the "R leaks" thread that something about the EF–R adapter made me wonder whether it would shut out third party lens vendors. I promised there to start a thread with more detail.
Please note that I'm talking about lenses mounting directly to the body, not via the adapter. I would not be expecting any more trouble with existing EF lenses than new EF bodies normally cause.
In this post I'll give some essential background about the electronic contacts on the current EF mount. In the next one I'll present some of what is known about the contacts in the RF mount, and what that might mean for the availability or not of third party lenses for Canon mirrorless.
The first attached photo shows the contacts on an EF lens, the 85mm f/1.8. Starting at the end with the wide contact, we have 6V for the lens motors, and then the power ground (the wide contact). On the bodies, the wide contact is actually two adjacent contacts. The next pin along is 5.5V, the 1980s standard voltage for TTL digital logic.
The next 4 contacts are the data link. This is what is known as synchronous, meaning the camera body supplies a clock on one of the 4 pins, and for each tick of that clock a 1 or 0 is represented by +5.5V or not on a pin. There is one pin for data going to the lens and one for data going the other way. The 4th pin is logic ground. This type of arrangement is called a parallel synchronous bus and was a perfectly reasonable design for the 1980s (in this case, it's a 1-bit bus).
This makes up the 8 contacts you see in your EF body.
The second and third images show the rear of a lens which can accept teleconverters, the 100–400 Mk II, and the lens end of a teleconverter, the 1.4× II. There are 3 more pins on the lens end of the teleconverter (the rear of the teleconverter has the usual 8, with 2 joined, and is not shown). The 2nd and 3rd of these pins are either shorted or not shorted to the 1st, representing 4 combinations: no teleconverter, a 1.4×, a 2× or something called a "Life Size Converter". The lens, not the camera, can then determine which of these 3 devices, or none it is attached to; it is the lens which then sends modified metadata (focal length, aperture, lens name) to the body using the normal 8 pins. This scheme has the advantage that teleconverters don't actually need any electronics in them, but from the vantage of 2018 seems almost prehistoric—Canon can't introduce another teleconverter with a different multiplier, because there's no way to tell the lens.
We can see that:
- the data link is an old-fashioned clocked one
- the teleconverter presence logic is contorted and inflexible
and we can see why Canon would want a new electronic interface for RF.
EF–R Pinout - will 3rd party lenses be locked out from RF mount?
I commented in the "R leaks" thread that something about the EF–R adapter made me wonder whether it would shut out third party lens vendors. I promised there to start a thread with more detail.
Please note that I'm talking about lenses mounting directly to the body, not via the adapter. I would not be expecting any more trouble with existing EF lenses than new EF bodies normally cause.
In this post I'll give some essential background about the electronic contacts on the current EF mount. In the next one I'll present some of what is known about the contacts in the RF mount, and what that might mean for the availability or not of third party lenses for Canon mirrorless.
The first attached photo shows the contacts on an EF lens, the 85mm f/1.8. Starting at the end with the wide contact, we have 6V for the lens motors, and then the power ground (the wide contact). On the bodies, the wide contact is actually two adjacent contacts. The next pin along is 5.5V, the 1980s standard voltage for TTL digital logic.
The next 4 contacts are the data link. This is what is known as synchronous, meaning the camera body supplies a clock on one of the 4 pins, and for each tick of that clock a 1 or 0 is represented by +5.5V or not on a pin. There is one pin for data going to the lens and one for data going the other way. The 4th pin is logic ground. This type of arrangement is called a parallel synchronous bus and was a perfectly reasonable design for the 1980s (in this case, it's a 1-bit bus).
This makes up the 8 contacts you see in your EF body.
The second and third images show the rear of a lens which can accept teleconverters, the 100–400 Mk II, and the lens end of a teleconverter, the 1.4× II. There are 3 more pins on the lens and the lens end of the teleconverter (the rear of the teleconverter has the usual 8, with 2 joined, and is not shown). The 2nd and 3rd of these pins are either shorted or not shorted to the 1st, representing 4 combinations: no teleconverter, a 1.4×, a 2× or something called a "Life Size Converter". The lens, not the camera, can then determine which of these 3 devices, or none it is attached to; it is the lens which then sends modified metadata (focal length, aperture, lens name) to the body using the normal 8 pins. This scheme has the advantage that teleconverters don't actually need any electronics in them, but from 2018 seems almost prehistoric—Canon can't introduce another teleconverter with a different multiplier, because there's no way to tell the lens.
We can see that:
- the data link is an old-fashioned clocked one
- the teleconverter presence logic is contorted and inflexible
and we can see why Canon would want a new electronic interface for RF.
Pinout - will 3rd party lenses be locked out from RF mount
I commented in the "R leaks" thread that something about the EF–R adapter made me wonder whether it would shut out third party lens vendors. I promised there to start a thread with more detail.
Please note that I'm talking about lenses mounting directly to the body, not via the adapter. I would not be expecting any more trouble with existing EF lenses than new EF bodies normally cause.
In this post I'll give some essential background about the electronic contacts on the current EF mount. In the next one I'll present some of what is known about the contacts in the RF mount, and what that might mean for the availability or not of third party lenses for Canon mirrorless.
The first attached photo shows the contacts on an EF lens, the 85mm f/1.8. Starting at the end with the wide contact, we have 6V for the lens motors, and then the power ground (the wide contact). On the bodies, the wide contact is actually two adjacent contacts. The next pin along is 5.5V, the 1980s standard voltage for TTL digital logic.
The next 4 contacts are the data link. This is what is known as synchronous, meaning the camera body supplies a clock on one of the 4 pins, and for each tick of that clock a 1 or 0 is represented by +5.5V or not on a pin. There is one pin for data going to the lens and one for data going the other way. The 4th pin is logic ground. This type of arrangement is called a parallel synchronous bus and was a perfectly reasonable design for the 1980s (in this case, it's a 1-bit bus).
This makes up the 8 contacts you see in your EF body.
The second and third images show the rear of a lens which can accept teleconverters, the 100–400 Mk II, and the lens end of a teleconverter, the 1.4× II. There are 3 more pins on the lens and the lens end of the teleconverter (the rear of the teleconverter has the usual 8, with 2 joined, and is not shown). The 2nd and 3rd of these pins are either shorted or not shorted to the 1st, representing 4 combinations: no teleconverter, a 1.4×, a 2× or something called a "Life Size Converter". The lens, not the camera, can then determine which of these 3 devices, or none it is attached to; it is the lens which then sends modified metadata (focal length, aperture, lens name) to the body using the normal 8 pins. This scheme has the advantage that teleconverters don't actually need any electronics in them, but from 2018 seems almost prehistoric—Canon can't introduce another teleconverter with a different multiplier, because there's no way to tell the lens.
We can see that:
- the data link is an old-fashioned clocked one
- the teleconverter presence logic is contorted and inflexible
and we can see why Canon would want a new electronic interface for RF.
Pinout makes me wonder whether third party lenses are locked out from RF mount
I commented in the "R leaks" thread that something about the EF–R adapter made me wonder whether it would shut out third party lens vendors. I promised there to start a thread with more detail.
Please note that I'm talking about lenses mounting directly to the body, not via the adapter. I would not be expecting any more trouble with existing EF lenses than new EF bodies normally cause.
In this post I'll give some essential background about the electronic contacts on the current EF mount. In the next one I'll present some of what is known about the contacts in the RF mount, and what that might mean for the availability or not of third party lenses for Canon mirrorless.
The first attached photo shows the contacts on an EF lens, the 85mm f/1.8. Starting at the end with the wide contact, we have 6V for the lens motors, and then the power ground (the wide contact). On the bodies, the wide contact is actually two adjacent contacts. The next pin along is 5.5V, the 1980s standard voltage for TTL digital logic.
The next 4 contacts are the data link. This is what is known as synchronous, meaning the camera body supplies a clock on one of the 4 pins, and for each tick of that clock a 1 or 0 is represented by +5.5V or not on a pin. There is one pin for data going to the lens and one for data going the other way. The 4th pin is logic ground. This type of arrangement is called a parallel synchronous bus and was a perfectly reasonable design for the 1980s (in this case, it's a 1-bit bus).
This makes up the 8 contacts you see in your EF body.
The second and third images show the rear of a lens which can accept teleconverters, the 100–400 Mk II, and the lens end of a teleconverter, the 1.4× II. There are 3 more pins on the lens and the lens end of the teleconverter (the rear of the teleconverter has the usual 8, with 2 joined, and is not shown). The 2nd and 3rd of these pins are either shorted or not shorted to the 1st, representing 4 combinations: no teleconverter, a 1.4×, a 2× or something called a "Life Size Converter". The lens, not the camera, can then determine which of these 3 devices, or none it is attached to; it is the lens which then sends modified metadata (focal length, aperture, lens name) to the body using the normal 8 pins. This scheme has the advantage that teleconverters don't actually need any electronics in them, but from 2018 seems almost prehistoric—Canon can't introduce another teleconverter with a different multiplier, because there's no way to tell the lens.
We can see that:
- the data link is an old-fashioned clocked one
- the teleconverter presence logic is contorted and inflexible
and we can see why Canon would want a new electronic interface for RF.
Adapter pinout makes me wonder whether third party lenses are locked out
I commented in the "R leaks" thread that something about the EF–R adapter made me wonder whether it would shut out third party lens vendors. I promised there to start a thread with more detail.
Please note that I'm talking about lenses mounting directly to the body, not via the adapter. I would not be expecting any more trouble with existing EF lenses than new EF bodies normally cause.
In this post I'll give some essential background about the electronic contacts on the current EF mount. In the next one I'll present some of what is known about the contacts in the RF mount, and what that might mean for the availability or not of third party lenses for Canon mirrorless.
The first attached photo shows the contacts on an EF lens, the 85mm f/1.8. Starting at the end with the wide contact, we have 6V for the lens motors, and then the power ground (the wide contact). On the bodies, the wide contact is actually two adjacent contacts. The next pin along is 5.5V, the 1980s standard voltage for TTL digital logic.
The next 4 contacts are the data link. This is what is known as synchronous, meaning the camera body supplies a clock on one of the 4 pins, and for each tick of that clock a 1 or 0 is represented by +5.5V or not on a pin. There is one pin for data going to the lens and one for data going the other way. The 4th pin is logic ground. This type of arrangement is called a parallel synchronous bus and was a perfectly reasonable design for the 1980s (in this case, it's a 1-bit bus).
This makes up the 8 contacts you see in your EF body.
The second and third images show the rear of a lens which can accept teleconverters, the 100–400 Mk II, and the lens end of a teleconverter, the 1.4× II. There are 3 more pins on the lens and the lens end of the teleconverter (the rear of the teleconverter has the usual 8, with 2 joined, and is not shown). The 2nd and 3rd of these pins are either shorted or not shorted to the 1st, representing 4 combinations: no teleconverter, a 1.4×, a 2× or something called a "Life Size Converter". The lens, not the camera, can then determine which of these 3 devices, or none it is attached to; it is the lens which then sends modified metadata (focal length, aperture, lens name) to the body using the normal 8 pins. This scheme has the advantage that teleconverters don't actually need any electronics in them, but from 2018 seems almost prehistoric—Canon can't introduce another teleconverter with a different multiplier, because there's no way to tell the lens.
We can see that:
- the data link is an old-fashioned clocked one
- the teleconverter presence logic is contorted and inflexible
and we can see why Canon would want a new electronic interface for RF.
Sep 10, 2018 at 08:15 AM
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