Canon EF Lens Aperture/Focus Electronic Control

S

shred444

Active member
So I've been discussing this on and off in the forum and I decided to group it in one thread here.

I find it interesting that canon EF lenses can be used in 35mm adapters, but none of the electronics in the lens are used. I have searched around and found several people interested in the protocol, but nobody has done anything about it. So I've decided to hack a SLR body and lens to decrypt the Canon EF Lens protocol.

In the end, I hope to have a wireless control able to provide aperture control and Follow Focus to an HV30, or any camera with a 35mm adapter, for that matter.

I just purchased an old Rebel (film) on ebay and a couple of EF lenses. The camera came today. I've also purchased an Extension Tube with Electronic pass-thru.

I'll keep you guys posted with images as I go. Comments are always welcome.

IMG_1673.JPG


IMG_1671.JPG
 
Sounds like a fantastic idea to me! I'm not that familiar with the Canon lenses - do the EF's have internal focus motors I guess? Good luck with the project!
 
They do. It's some sort of magnetic vibrating system. The aperture uses a small servo motor to adjust the fins.

With the electronic focus, follow focus can be designed without the ugly looking gear system. Just a wireless remote.
 
Ahh cool. Having the wireless follow focus ability would be pretty slick. My question would be if the servo can operate smooth and slow to perform a good rack focus. The only time I ever see AF in operation its quick and sharp (for good reason). How about computer controlled focus pulls? Set the beginning and end and duration. Software calculates a nice smooth start and stop? That could be interesting...
 
Hi,

If you are able to design a system to control the aperture as well as an intuitive follow focus interface then you have solid ground for a great product!
 
jdajda said:
Ahh cool. Having the wireless follow focus ability would be pretty slick. My question would be if the servo can operate smooth and slow to perform a good rack focus. The only time I ever see AF in operation its quick and sharp (for good reason). How about computer controlled focus pulls? Set the beginning and end and duration. Software calculates a nice smooth start and stop? That could be interesting...
Click to expand...

I agree, rack focus may be difficult. If the focusing system works on absolute coordinates, then I can use the computer to increment the coordinates by the smallest amount possible. It's tough to say right now... but we will see
 
Pinout and pin functions for the record:

Left to right, looking at the front of the body:

1. VBAT
2. P-GND 3. P-GND (pins 2 & 3 are common on the lens)
4. VDD
5. DCL
6. DLC
7. LCLK
8. D_GND

Pin Functions
VBAT - Motor power
P_GND - Motor power ground
VDD - Logic circuitry power
D_GND - Logic circuitry ground
DCL - Data from body to lens
DLC - Data from lens to body
LCLK - Clock

Data protocol: Motorola SPI; 8 bit serial; Such as the protocol used with the 68HC05 chip.
 
Ahh geez I actually took a course in college and had to work with the 68HCsomething a rather. I of course will be of little help as I failed the course and subsequently dropped out... Err so anyways a rudimentary FF could be done just with control of voltage in pins 1 and 2? All the logic stuff could be cool to play with though and I assume are what control the iris?
 
I dont think so, Pins 1 and two supply power to the moters, but they are most likely controlled via PWM from an embedded microcontroller. The logic SPI stuff is what tells the microcontroller what PWM duty cycle and frequency to output to the motor.

This is obviously all subject to change when I get my equipment and start hacking
 
You must log in or register to reply here.
Back
Top