Canon 28-70 F2,8 lens – optical problem caused by aging

I repaired a Canon 28-70 F2,8 lens for somebody, with complete cleaning of the internal elements. The repair was ok – but the image was very smooth.

Controlled with a strong handlamp, I have seen a haze on one of the inner lenses.

After disassembling, I have found the problem. The double aperture module has a composed lens. Unfortunately, it is composed of two glued assemblies – and the problem is on the contact surface of two glued ones…

Now I have to find out the way of disassembling and reglueing them.

IMG_0441 good lens

IMG_0440 lens with deposit (in this case unfortunatelly  damaged glue between the two elements)

IMG_0437 aperture module



IMG_0443 glued lens group

About canonrepair

Ruzsa János. Amatőr fotós, Canon DSLR váz. Amateur photographer. Canon DSLR user.
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12 Responses to Canon 28-70 F2,8 lens – optical problem caused by aging

  1. canonrepair says:

    And yes, by cementing the lens there is a problem of keeping them aligned during the UV curing. Here is no other better solution: case it fails, disassembling and doing it again.
    The decision is simple: to do this- or to throw away the lens.

  2. canonrepair says:

    I am NEVER joking in matter of camera and lens repair.
    Instead a very expensive official bench I have an own method which works approximately in the same way. Optical alignment has the scope of minimalizing the optical distortions. There are two types of alignment: radial position and tilt (angular position) regrding to the optical axis. Case You have a misalignment then:
    – a bright dot will be not a dot, rather a distorted patch, (radial misalignment)
    – the right/left or the upper/lower side will be not the same sharp (angular misalignment)
    The first one causes a strong ASYMMETRIC chromatic aberration in the middle too – so I do the alignment till the chromatic aberration is symmetrical.
    For the second one I have to make the adjustments till the picture will be uniformly sharp on each side.

    Which problem do you see here?
    By the way, if I want to do the adjustment on the infinite, I use a collimator made of an old filmcarera and a tele prime lens..

    • agittins says:

      When using an old film camera + tele lens as a collimator, how critical is the accuracy of the infinity position of the tele lens? Will the setup have to be carefully calibrated for infinity focus, or does the maths work out to make the setting not critical, and an approximate focus is acceptable?

  3. Lopes cardoso says:

    Are you joking Ruzsa János? How do you expect to do the optical alignment? Do you have any kind of optical alignment tool?

  4. robertozuena says:

    i im roberto from rome i have the same problem with a canon 28 70 f2.8l do you know how disassemble the two little lens? tnks a lot for youre informations roberto

  5. canonrepair says:

    yes, thanks, this was one information, which gave me some hope 🙂 The damaged lens has an effect like a blur in the photoshop…

  6. Ben says:

    Did you see this tutorial?

    I bet you can do it! What kind of image issues are you having? Does the haze affect the contrast, detail? Have fun!

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