Repair and disassembly guides for SLR, DSLR, and mirrorless interchangeable camera lenses.

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calibrating the aperture assembly on a canon 24-105 F4L

i replaced the aperture flex cable of my canon 24-105 which was badly torn and causes err01 when i try to use my lens. but i was not able to make a careful mark on the 3 eccentric setscrews that is used for the alignment of the 3rd group optics in the aperture assembly. now i am able to use my lens but all images captured are not that sharp as before and compared to my other lenses i can really say that my 24-105 is bad and out of calibration. i need a guide to calibrate the 3 eccentric setscrews... i found some guide somewhere but it is not clear how.. i need in layman's term if possible with illustrations

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There is two ways you can do this:

The first is using a collimator which is an artificial image set to infinity this is how the pros adjust lenses in the shop. Edmund Optics Vid on collimation

The other is on a clear night with a visible moon use it as your target. Adjust the lens so it is set for the most zoomed in and set manually for infinity. Adjust the lens group so the image is sharp that should do it.

Here's one other method using a second camera Using a second SLR camera as a collimator

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wow, thanks alot Tom Chai.. i will try this one... i will look for other slr camera to be used as collimator


FYI - It was Dan not Tom that offered you that answer ;-}


This is real hardcore stuff. I never tried to repair optical equipment. I usually just replace the entire module


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You'll need professional equipment. There is a reason why the lens are so expensive

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ray floyd will be eternally grateful.
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