Basically I am guessing it involves grabbing the signals from the adapter, then somehow stepping those up voltage/current-wise (with relays or transformer) to drive the motor back and forth. My guess is it must have an external power source since I doubt the camera could drive a motor that big off it's internal battery.
Ed Sawyer wrote:
Basically I am guessing it involves grabbing the signals from the adapter, then somehow stepping those up voltage/current-wise (with relays or transformer) to drive the motor back and forth. My guess is it must have an external power source since I doubt the camera could drive a motor that big off it's internal battery.
I don't think the contraption can AF at all. I think it just uses an electric motor powered by a car battery to grind the MF ring back and forth.
Sorry for the late reply. It is a working model for sale. From the seller, the AF function actually works. As I know, EOS mount has 5V power supply which will power the electric motor.
PS. the black box underneath is probably the controller PCB taken from a working lens, that will be used for communication to camera body. Before USM was invented, convention electric motor was served for AF. It is poosible to add a motor to the contoller, so that it will drive the focus ring by the camera.
Gotta give credit for the hack there. No infinity focus though. The Canon lens system uses a high level signalling system, not just stepper motor signals (for example, the camera can command the lens to go to infinity focus, or step focus closer one notch.) You will notice it is not a 1.4 converter that was used as the adapter, rather a shell from a lens. This is important, as you need to have the microprocessor from donor lens to convert the lens protocol to the stepper motor signals. In this case, the stepper motor signals were probably amplified and sent to the large focus motor seen. Likely with an external power supply for the motor buffers, but who knows how much the EF interface can supply? Since the lens does not have an electronic aperture, and it is unlikely to get from the aperture stepper motor settings to a calibrated aperture mechanical movement, I suspect it is stop down metering only. Another drawback would be that canon focus algorithms (at least the stepper motor part of it) are tuned to the individual lens, so the focus performance might be sluggish, or overshoot easily.
So, what we have here is a poor focusing, stop-down metering, no infinity focus, 500mm f/4.5 lens. Not too appealing from a working lens, but an interesting intellectual exercise (and my hat is off to them on this point.)
Great engineering! As Dark Slider mentioned, I wonder if you have infinity focus with the new EF mount. That is normally the most annoying part that you can't easily use FD lenses with Canon EF-cameras (only with low-quality glass adapters or with extension rings where you lose infinity focus).
Don't see it on their museum, but didn't Canon have an autofocus lens for the old FD (T series?) before EOS appeared? I think the sensor was sitting next to the lens instead of looking thru the camera. I wonder if it's the same idea borrowed from that setup.
As for infinity focus, the rear is hacked and converted so it may reach infinity.
Indeed, the rear could have had the registration distance shortened so infinity focus is probably available on this, Id' think. If you are good enough to hack on AF, getting infinity would be trivial.
Personally, Id' leave it MF, or else buy the EF verison.
Did anyone else notice the serial number? Collectors normally pay big bucks for low or interesting serial numbers and at 10007 I would figure that this qualifies. I wonder if the lens would have been worth a whole lot more than the average before its conversion.
My god! Did you do that? If it works, I'll be impressed. If it works well, I'll be VERY impressed. What's the story?
