Hack Canon EOS 300D to Confirm Focus With All Lenses, Permanently.




About: I love fixing things...

Well, right, you can do this easily by using various chipped adapters for several lens mounts - but how about permanently modifying your camera to do the same and avoid paying extra for multiple adapters? I love my 300D but I don't own any EF/S lenses, all my arsenal is from 1980s, gorgeous manual focus lenses from Olympus and Carl Zeiss.

Canon EF mount has a register distance which lets us use Olympus OM, Pentax M42 and K-mounts, Leica R, and Contax mounts with proper adapter rings. These are vastly available on the net for purchase (ebay). However, Canon EOS auto-focus system needs a lens to speak to itself to work. The lens communicates its focal length and aperture values and the camera activates AF after confirming these. Some clever chaps cracked the code and embedded it in a tiny PIC chip and slapped those on Canon EF adapters for manual lenses.

In this hack we'll permanently embed one of these PIC chips in the camera. This hack requires some disassembling and soldering skills. I can rate it at medium hardness.

You need:
- One AF confirm activating chip for Canon EF mount (ebay keywords: Canon AF confirm chip)
- A tiny switch (if you want disabling functionality)
- Thin wires
- Epoxy (optional)
- Philips 0 and flat screwdriver
- Soldering iron and solder
- Self adhesive tape/ribbon

Do not put the battery in the camera when it is disassembled, even if you have it in off position. There are live circuitry in it and you may accidentally short it - burning out some fuses (I'll write another instructable about fixing those, later). AF confirm chip is a tiny pic chip and can be affected from static discharge easily, so be careful while you are working with it.

DISCLAIMER: Like all other hacks, this will void your warranty (I don't know if there are any 300D left with warranty anyway). Also involves exposing flash circuitry, if you are careless you may experience a high-voltage electric shock even when the battery is out (which I did briefly). This hack may render your camera totally useless, so if you brick it don't blame me, but put it on ebay for parts (others will like this). I am not responsible for any of these above if you experience a problem.

REFERENCE: There are few places where I borrowed wording from Gary Honis's excellent instructions on Canon EOS 300D IR filter removal. Check out his site for an alternative take on disassembling. However, we don't have to deal with the mainboard, so don't strip your camera to barebones like he did.

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Step 1: Prepare the AF Confirm Chip to Fit in the Camera.

Well, I bought the chip already installed on an OM/EF mount adapter.

I had to soak it in acetone to soften the epoxy. After a few minutes I could shave it off the metal adapter easily (Photos 1-3).

However, during the process I damaged the chip/board assembly and got the chip de-soldered off the board (Photo 4).

I then soldered thin wires to the tiny PIC chip and mapped its pins on a paper (Photo 5).

I finally embedded the wired chip in a drop of clear epoxy. Now the chip is ready to be soldered on the camera.

If you just bought the chip separately (not like me), I advise you to solder thin wires on the pins of the board, and map them to the ones on the camera (and solder them permanently following my next steps).

Step 2: Disassemble the Rear Cover!

This is not very hard, you just have to play by rules and follow several steps.

1- Take out the strap, battery, rubber eye cup and CF card, put a body cap on to keep your mirror box clean.

Now remove the rear panel by doing the rest:

2- Remove grey plug on back of camera that covers a screw and remove the screw (Photo 1)
3- Remove three screws at bottom of camera (Photo 2)
4- Remove two screws under CF compartment cover (Photo 3)
5- Remove two screws on the black rubber panel (where you have ports - Photo 4)
6- Remove the black rubbery black panel and rubber port cover by popping it out from the bottom edge using a sharp knife (Photo 5)
7- Now you can gently take the rear cover out but be careful there is a flat ribbon cable connecting the LCD and the buttons on it to the mainboard. You have to remove that from the mainboard. The ribbon cable does not just pull out of its connector. Instead, the connector is a "hinged type". The connector is color white and its hinge is black. There are two small black hinge tabs at each end of the connector. Lift these two tabs upward with a small flathead jewelers screwdriver and the black hinge will rotate upwards into a vertical position. This releases pressure on the ribbon cable and the cable can be pulled out with the rubber tipped pliers. (Photo 6)

Now you exposed the mainboard of your camera. But that's not enough. We need to access the front face of the camera where we need few soldering job to do. We'll do that in the next step.

Step 3: Remove the Front Panel!

Now this is not more tricky then the first one. The photos below may show the mainboard removed, but this was because I didn't know the exact routine and had to do that way. Do not remove the mainboard, you don't have to. Just do what it says in the next steps:

1. Remove four screws at the base (one is different don't mix them) (Photo 1)
2. Remove two screws near the grip (Photo 2)
3. Remove the battery door by pulling the springy hinge connector (Photo 3)
4. Remove the battery door hinge by unscrewing two screws (Photo 4)
5. Remove the plastic cover to expose holes to access grip screws (Photo 5-6)
6. Remove two screws connecting the grip on the body (Photo 7)
7. Remove two screws from front (Photo 8)
8. Pop out the flash by forcing it, or do it in advance (Photo 9)
9. Pry the front casing out, off the tripod connector. Be gentle (Photo 10)
10. Check out your work area now (Photo 11)

Step 4: Solder the AF Confirm Chip Permanently on the Camera!

Once you have the front casing off, 6 tabs for soldering the chip are exposed (Photo 1). You have to short the black and green cables to fool the camera that there is a lens installed (Photo 2). Hide the AF confirm chip somewhere under the bottom metal panel (Photo 3). Use adhesive tape/ribbon to cover your job cleanly and nicely. More information is on the photos as notes.

I may be wrong on the pin-out below, so please test it with a multimeter.

Put your camera back together, put the battery in and see if the tiny chip is reporting a lens. In my case it reports a 50mm f/2.0 lens. This varies to what you have on the chip. You can ask the seller of the chip to program a specific number for you, too.

Step 5: Some Final Thoughts...

Well, you can avoid all the hassle by buying several chipped mount adapters for the starts. Maybe I am a cheapo (I bought the camera for £40 and repaired it anyway). I already had several 'naked' adapters, and I wanted to have the confirmation chip embedded in my camera.

Now I can put many gorgeous manual focus lenses on my camera and still have AF confirmation (like this superb Olympus Zuiko 35/2 - Photo 1). AF confirmation chip simulates a 50mm f/2.0 lens as seen on Photo 2. The tiny switch enables/disables the built in AF confirmation chip. It is nicely hidden in battery compartment.

Well I guess I should say: I modified it, because I can. :-) It was fun.


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    17 Discussions


    11 years ago on Introduction

    Very nice! A long time ago I was trying to figure out if this was possible or not and gave up pretty quickly. I've always wondered if it would be possible to do this with some sort of hacked firmware though, I don't think I'm up to the challenge of actually taking my camera apart. Nice work!

    3 replies

    Hi, hacked firmware is the way to go actually, but there are not many digging those I guess. I don't see any reason for not being able to do that with a firmware hack. You can always buy chipped adapters for your camera. These days they go around £15-30 depending on the type you need. Chees, Koray.


    Reply 7 years ago on Introduction

    Great Hack! You seem to be the right person to pose my question regarding the communication bus.

    Basically my questions have to do with the use of old manual lenses on digital DSLR . Specifically the new Sigma SD1 DSLR.

    This digital camera , latest model from Sigma Japan, incorporated some new abilities over the previous Sigma models , such as Tethered control , that are obviously lens dependent , so the camera seems to be always polling for lens id and any attempt to use manual lenses that do not report back their id , create problems with the generation of a JPG for LCD Display . The RAW capture remains unaltered and fully usable.

    This might be a bug of the Firmware that does not have an exit strategy for when there is no lens attached ( A non electronic lens is essentially invisible to the camera )

    Since for most people the LCD display and its Histogram are very important to achieve good Imagery I am trying to find a way to fool the camera into thinking that a lens is still attached .

    The previous models did not have this problem and the last lens ID and data were retained in non volatile camera memory. The new model does temporarily retain id and data of the last electronic lens that was mounted if HOT swapped by a manual lens but it will loose it on shutdown .

    Any ideas to create persistence of the lens id ? I would not dare tinker with enigmatic Firmware code. My thinking is around the possibility of pulling some camera pins low or high , to tell the camera that the lens is busy doing something .Do you think that this might work?

    There are many Chinese lens adapters for Canon EF mount that incorporate a chip that apparently responds to the camera in some fashion to re-enable the AUTO FOCUS ASSISTANCE viewfinder's LED light and Beep , that were lost when a non responding lens was mounted, forcing the camera into Manual Mode.

    Do you or anybody know how those chipped lens adapters work to make the camera focus assistance work? A similar concept might be derived from there to create a "Virtual lens" for my Sigma camera based on the similarity of the communication bus (SPI)

    If I can understand how those chips work maybe I can use them in the Sigma SA bus that is very similar to Canon EF


    Reply 7 years ago on Introduction

    Hi! Thanks for your kind words.

    I am surprised with that strange behaviour in SD1 firmware, it certainly is a bug. Your quest is interesting, and there is a high chance you can succeed I think. I remember reading about the similarity between EF and SA protocols. Here is a thread in which this is mentioned:


    The focus confirm adapters for EF mount had many new iterations after I posted this instructable. The latest ones can be reprogrammed for the max aperture or focal length while they are on the camera, AFAIK.

    If I were you I would get a cheap simple EF focus confirm chip from ebay and press it on the SA mount with fingers to see if it works.

    The pinout and functions of SA and EF are exactly same according to commenters in the above link. These chips (which are tiny PICs) replicate the lens ID signals of known EF lenses (i.e., 50mm, max aperture f/2.0) and fool camera into thinking that the manual focus button is on. Then the camera turns the focus confirmation on and registers lens ID as 50/2.

    There are few Sigma SA mount adapters for M42, and I think attaching the focus chip on the adapter shouldn't be a very hard task.

    I think it is worth a try.



    9 years ago on Introduction

    What's name of this chip?
    I think maybe it is a EEFROM
    We can read all data inside this chip and write to another chip


    10 years ago on Introduction

    hi, how does this work if you want to attach EOS digital lenses? do you need to remove the chip again? thanks

    1 reply

    Reply 10 years ago on Introduction

    There is a tiny switch that controls the power to the chip (between Vcc and chip, I can't remember which line). If you disconnect it the chip is deactivated and EF lenses can be recognised right away. K.


    11 years ago on Introduction

    This looks amazing, you did a great job. Just that I can't afford this camera and I would not be brave enough to hack.

    2 replies

    Reply 11 years ago on Introduction

    I think I didn't have much to lose, I bought it for £40 anyway. If it got fubar (=D) I could still sell it on ebay for a profit. :-)<br/><br/>K.<br/>


    11 years ago on Introduction

    Great instructable but my wife will never let me do it to her camera;)


    11 years ago on Introduction

    Very well done Instructable, although I don't think there's many people wanting to fubar their cameras. =D

    1 reply

    Reply 11 years ago on Introduction

    FUBAR! I loved that term. In my vocabulary, now!.. :-) Thanks, I am glad that you liked it. By the way, one can always buy a chipped adapter ring and keep the screws on their camera. :-) K.


    11 years ago on Introduction

    Excellent instructable, an important thing to note is that this is an excellent way to breathe some life into older lenses, maybe FD lenses in my case from my old canon A-1 and that this instructable can help those work in ANY EF mount lense, even an older cheaper 35mm camera such as the A-2. It doesn't have to be used just on new digitals. A good thing to note when going shopping for second hand cameras isnt what they can do, but what they can be MADE to do... Thanks for the instructable!

    1 reply

    Sadly, FD lenses are of no use! :-( The registry distance of FD lenses are shorter than EF lenses (42mm<44mm), which is a shame (you can't reach infinity focus - close focus or macro OK). Canon evidently wanted to sell many more lenses with their then new EOS line-up. The only way to use FD lenses on EOS is permanently modify them (some cutting, gluing involved), or use them with optical adapters (image degradation). But, lucky we are, Pentax M42, Yashica/Contax, Nikon, Olympus OM, Leica R, Pentacon Six, etc are all gorgeous lenses that can be utilized on Canon EOS cameras. I am not a big fan of Canon lenses, anyway, so Canon bodies with old-time awesome lenses is good to go for me!.. :-) Thanks for your comments!.. K.