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_0438

IMG_0442

IMG_0443 glued lens group

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About canonrepair

Ruzsa János. Amatőr fotós, Canon DSLR váz. Amateur photographer. Canon DSLR user.
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7 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..

  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

    • canonrepair says:

      you have to submers it in a special mixture of solvents, and wait, wait, wait….
      I use to accelerate this a vacuum pump: making vacuum above the fluid, then letting the air again in the bottle accelerates the protuding of the solvent in the inner side of the lenses. But take a lot of time, and after then You have to glue it very precisely.

  5. canonrepair says:

    hi,
    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?

    http://www.skgrimes.com/library/old-news/old-lenses-can-be-restored-by-re-cementing

    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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