EF 24-105mm f/4L Soft and Hazy

[wilmark]

I have the above lens that is very soft and hazy - but i cannot see any dust or mold. I think i want to try to tear it down and see if i can do anything with it.  Like this guy is doing here: 

https://www.youtube.com/watch?v=bdShwMk-LDc

But he says that the "Axis Test" showed poor results early in the video. I gather that some of the elements are misaligned causing the blurriness. I'd like to confirm that it is indeed an axis problem. Any idea what exactly is an axis test? What charts are used? Is it the same as a lens calibration test?

[Brummel]

Recently changed apeture unit as cable broke. After i got smudgy and not clear image but focus was on right place. So there is 3 tiny screw to calibrate that chromatic abberation. You need a pinhole with back light to see that shape. You will never able to get back same as from factory. I calibrated mine but i got flares, smudy image on edge still. I cleaned again all glasses inside. Mine apeture unit came from ali express. So i guess that parts miss alligned too. I think canon repair centers use these parts also. So you can try but never will be perfect when lens came out from factory. There is 3 other screws on back which glued but i think need to adjust also. 

[Brummel]

No official test. You zoom in 105 cm to max. Set manual your focus. Than you make a hole on something around 1cm. You put a white paper behind and use a toch to create that light. Than on viewfinder you can see and use that 3 screw to calibrate to get perfect circle.

[wilmark]

"It is highly unlikely that Canon returned a faulty lens. Not impossible but surely way improbable."

You are making a generalized point that might be true about the entire 'population' of canon repairs. But factually i know that to be entirely false in my case (n=1, this particular case). Canon repaired the problem and it no longer focused. I took long to resolve it because of the logistics i explained earlier, but you dont know how things slip through and they have mitigation (like you can call them and they will repair free again). But this lens was returned faulty, you may not know why, a lapse in the process QC. These kinds of issues are not isolated. I have had similar problems with Nikon. There are tons of warranty fraud by large established companies, that have been exposed. Asus, Newegg comes  comes to mind. I have seen in where i live with Toyota of all companies, and its not a dealer, but the actual Toyota Company. It is very easy for the service person to have erred and not re-assembled the lens back up properly and shipped it off. And i might very well take the lens apart and learn a thing or two in the process, it is largely worth less piece of junk at this point. 

[Stephen]

No @wilmark.

We're not going to come on to the Canon USA Community and accuse Canon USA of warranty fraud. 

If your camera was repaired by Canon USA, you need to contact support for a re-evaluation. Contact support at 1-800-OK-CANON (800-652-2666) to start this process.

If you are outside of the United States, contact Canon in your country or region for assistance by visiting https://global.canon/en/support 

[wilmark]

I did not accuse Canon of warranty fraud - i only pointed out that it exist. I only know that because of how chose to deal with the particular problem because i did not live in the US, having purchased considerable product, and ended up needing repair service, that the item was returned in a unrepaired state with new issues. Because of the length of time that elapsed from the time it was shipped back to me, i was unable to identify and raise the issue with canon within your stipulated time frame. I accept this. This does not change the facts i previously outlined. I did contact them, and they told me to send it back and pay for it to be examined / repaired again - i said "no thanks". 

[Ron888]

I sometimes encourage people to fix simple things on lenses.In this situation i cant. The chances of fixing the issue without complex testing equipment is close to zero