In lens focus microadjustment

In lens focus microadjustment – is it possible?

Of course it is. In fact, each lens of each type is a little bit different from the averedge lens – so the camera will react different with the autofocus.

As  You probably know, in the camera there are 3 optical systems, which have to be adjusted on to the other: the cmos, the AF-system and the optical viewfinder. They are adjusted mechanically in the factory, after then adjusted by a software too – but they would work precisely only with the master lens, with one single focal distance.

As we use lenses with different properties, we have to tell this to the camera, and the camera will make the recalculation (or compensation) for the given lens. This is why a manual lens with an emulator chip will work well only if the chip is programmed for the real focal length.

But lenses are different each of them, so there is a possibility for a second correction, which is stored in the lens and will be transmitted to the camera. By the older lenses the needed correction was determined by the factory and marked on the lens board very simple: in the form of some soldering pads, which can be shorted or not by a little soldering. Each pad reperesents a bit, and with a table You can understand, if the lens was programmed to a little bit backfocus or frontfocus.

You can ask me: ok, but why is this interesting, if it has been set by the factory. the answer is simple: at first, I like to know, how thinks work. At second, the users camera is not a master camera, so the camera itself can have a front or backfocus, and after a repair the lens could be other then before – so there is a need of adjustment.

What i know is, that the EF 50 mm F1.4 lens and the EF 85 mm F1.8 lens have this possibility, and works!

EF 50 mm F1.4 

IMG_5984_1  IMG_5991_150mmF1.4 soldering pads 

I made some experiments with the pads (You need just an 8 pol DIP switch ans some thin wires), and it seems, the here are used only the pads with the numbers: 3, 4, 5, 6.

The focus correction is given for the vertical (V) and the horizontal (H) direction. Can be in plus (backfocus) or in minus (frontfocus).

pad   effect
3   V-
4   V+
5   H-
6   H+

By the EF 85 mm F1.8 You have this:

ef 85 mm F1.8 soldering pads

pad   effect
1   V-
2   V+
3   H-
4   H+

In this case the setting to + or – has given a modification of ca. 0,5% of the distance to the object.

Try it!

About canonrepair

Ruzsa János. Amatőr fotós, Canon DSLR váz. Amateur photographer. Canon DSLR user.
This entry was posted in General topics. Bookmark the permalink.

11 Responses to In lens focus microadjustment

  1. ded0t says:

    and how it’s ‘8 pol DIP switch ans some thin wires’ works?
    can you explaine more detail about it or maybe demonstrate in video?
    thank you

    • canonrepair says:

      Hi, no, sorry, I dont have time to make a video.
      Electronic devices can be programmed with DIP switches. This means, case You have for ex. 4 entries on a processor, all pulled on +5V with a resistor, You can switch GND for them. The processor reads this entries, and modifies its characteristic according to that.
      So the DIP switch was only for a temporary experiment, to see, how reacts, but without being necessar to take the lens apart for each step, just activating the switches.
      After making the experiment, you have a logical table, which combination is the right for you, so you take out the DIP switch, and just make the corresponding connection making a soldering bridge on the pads.
      That’s all.

  2. Adam says:

    Hi, i rescue my canon 50 1.8 II whit tis tutorial. I also have Yongnuo 50 1.8 whith very front focus. Mayby you look for pcb of this lens, and try to found calibration points of corse if it posible.

  3. Martynas says:

    Hello. I have Sigma 50mm 1.4 EX HSM for canon. Glases are in ideal positions and I think that problem is in lens firmware. Any ideas how to repair it? There is very big back focus.


  4. jurek says:

    There seems to be more than one type of main pcb in 50 f1.4 lens. Do you know if non-software lens adjustment is available in all of them?

  5. dbob says:

    Arról van valami infód hogy egy 17-55 esetében mennyivel fejlettebb már ez a korrekció?
    Backfocus-os az obi, és jó lenne korrigáltatni rajta. Ám ha ilyen kötött rá a lehetőség mint ennél a két obinál, inkább a vázon belül igazítok rajta mintsem bevigyem Camera Kft-hez.

    • canonrepair says:

      szerintem abban csak szoftveresen lehet beállítani, akkor pedig abszolút pontosan és finom lépésekben.
      ha a vázadon van microadjustment, akkor inkább abból állítsd be, az ingyen van.

      • dbob says:

        Köszi az infót.

        Azért vinném szívesebben szervizbe, mert már tisztítani is kéne belülről…szívja a port ahol tudja konstrukcióból kifolyólag.

        De már ez is megnyugtató hogy valószínűleg tudnak majd kezdeni valamit, nem úgy mint anno az 50mm 1.4-esemmel. Úgy adtak vissza kb., mint ahogy beadtam (hiszen limitált az utánaállítási lehetőség), de a cash-t lenyúlták 🙂

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