What is a focusing screen??

[neurorx]

I sent in my camera to Canon service center as my 24-70 F2.8 II seemed to have erratic autofocus being soft in some instances. My other L's were perfectly fine. The 24-70 seemed to be ok then not with no particular lighting or situation I could Id. I tried micro adjustments and still didnt help as no abnormality in focus could be clearly found. I sent my lens in per request, they changed the focusing elements and said if the focus issue recurred to send the camera and lens to test them together. So, I sent my lens and Canon 5D Mark III to Canon per request and they said they replaced the camera focus screen??? From my reading I have no idea how this would be an issue to cause erratic focus in one lens out of my other eight lenses. They hadnt even tested the two together and made this conclusion.

Canon first recalled and asked me to send in my camera that was packed with my lens and I had already made a prepayment for no identified service.

Did I just pay 250 bucks for something that will make no difference and possible the issue is a bad lens copy??

Any one have any insights???

Thank you.

 

[neuroanatomist]

The focusing screen sits in the optical path just before the pentaprism, on the way to the viewfinder. It has absolutely no effect on autofocus (although it can affect metering and manual focus).

 

[neurorx]

That's what I got out of my reading...I feel pretty messed over.

 

[neuroanatomist]

Call them and have them explain in detail how replacing the focus screen corrected the AF problem...

 

[neurorx]

I did. They said it was their mess up and that they hadn't tested the lens and camera together...

No good explanation of why they thought that would fix the issue.

Neuroanatomist...Neuropharmacologist....good to meet you.

 

[mitchel456]

i had to have a focusing screen be fixed
and yes metering is just off with out it

 

[Eldar]

I had a similar issue with my 5DSR. It was OK with the majority of my lenses, but I had to make significant adjustments when i micro adjusted lenses, all in the same direction. In particular the 35 f1.4 L II was quite inconsistent on AF. I had it in with CPS and they said that they had to make a Mechanical adjustment to the AF path, apparently to offset a fixed deviation. After that the I had to rerun AFMA, which was reduced from +17, +18 and thereabout, to about +/- 2 or 3. AF is now very stable and I have nothing to complain about. If they claim they fixed it by changing the focusing screen, I would be very sceptical. I use several focusing screens on my cameras and they do not interfere with AF. And if it was, a focusing screen is about $35, so you should claim your money back.

 

[neurorx]

Canon said they messed up and hadnt even tested the two together though all the notes and the fact they were shipped together wasnt noted. So they are retrieving the camera and sending it back to be retested. Ive requested my money be refunded and a list of anything done to the camera.

Given the variability in the autofocus, could it just be a bad lens? I dont have the issue with any of my other lenses.

 

[Eldar]

Canon said they messed up and hadnt even tested the two together though all the notes and the fact they were shipped together wasnt noted. So they are retrieving the camera and sending it back to be retested. Ive requested my money be refunded and a list of anything done to the camera.

Given the variability in the autofocus, could it just be a bad lens? I dont have the issue with any of my other lenses.

You find yourself in a situation where they will claim that everything is OK, unless you can prove otherwise. What you need to do is to claim that all other lenses are OK, which means this particular one is causing the problem. Are you able to test another copy of the same lens? If that works, you have a strong case.

A good advice (I think) is to be persistent and let them know that you know what you´re talking about, especially if you do ...

 

[slclick]

Something you can't change in a 5D3......

 

[neurorx]

I explained all that had been tested and evaluated with respect to mircoadjustments, focus points etc. explained all my other Ls don't share the issue and that my local camera store agreed it was a variation in the lens as they noted the same and recommended Canon review as well. I thought at first is was a technique issue but nothing would fix it and it wasn't shared on my other lenses.

So I'll keep pushing.

I haven't been disappointed with Canon until now.

 

[Don Haines]

Neuroanatomist...Neuropharmacologist....good to meet you.

OMG! Now there's two of them!

Welcome to the forum!

 

[neuroanatomist]

Neuroanatomist...Neuropharmacologist....good to meet you.

Likewise!

 

[neurorx]

Thank you Kind Sir!

 

[Mt Spokane Photography]

Hopefully, they will get things sorted out. The $250 is a minimum repair bill for ordinary repairs. Obviously, you should not have been charged for that if they did not fix the issue you complained about. Focus screens do get scratched, the tech may have noticed that, but they need to fix it. Since they recognized that they did not do the repair and have sent a label to have it returned, it sounds like they will get it done right.

 

[martti]

Neuroanatomist...Neuropharmacologist....good to meet you.

Likewise!

I used to be a neuroanesthetist but that was twenty years ago...now I just put people to sleep and take their money...if they wake up.

 

[AlanF]

Neuroanatomist...Neuropharmacologist....good to meet you.

Likewise!

I used to be a neuroanesthetist but that was twenty years ago...now I just put people to sleep and take their money...if they wake up.

Sydney Brenner used to say in the good old days before pdfs when we had to economise on photocopying: Don't Xerox, neurox!

 

[neurorx]

Neuroanatomist...Neuropharmacologist....good to meet you.

Likewise!

I used to be a neuroanesthetist but that was twenty years ago...now I just put people to sleep and take their money...if they wake up.

I do research, not as much as I like to as they tend to put you in more administrative jobs when you get older.

I guess that approach wouldn't affect your HCAP scores as much.

 

[neurorx]

I am still nervously awaiting the return on my babies.... ;D :-\ hoping that all is ok with both of them.

Is it just me or does everyone experience separation anxiety when they give their gear into be cleaned or repaired?

 

[Luds34]

I am still nervously awaiting the return on my babies.... ;D :-\ hoping that all is ok with both of them.

Is it just me or does everyone experience separation anxiety when they give their gear into be cleaned or repaired?

The couple of times I've sent something in it was faulty/broken so things couldn't get any worse.

So take the optimistic approach that you're gear is only getting better.