Serious back focus issue with my 500mm f4, but only on my 7D.

I've been using my 7D ever since they first came out and I have never had an issue with it. It works great with my 70-200, 300mm f4, 400mm f5.6 and any other lens I have used it with. I recently purchased a Canon 500mm f4L IS version 1 and from day one I noticed a focus issue with the lens on my 7D.

I attempted to MFA and it needed -18 to get the focus to look right. This seems like a lot to me. What complicates this though is that the lens works absolutely perfectly on my 6D with no MFA required. Today I took it back to my friend that I bought it from and tried the lens on both of his 7D's and his 1D Mark IV. On both of his 7D's the results were the same, -18 MFA to get it right. But on the 1D Mark IV it was perfect at 0 MFA.

It is an older lens, the date code is from 2000 so I thought maybe the autofocus chip was having a compatibility problem on 7D's, but the fact that it works perfect on even newer cameras like my 6D and the 1D Mark IV has me really stumped.

I am a CPS member and I want to send the lens to them with the 7D, but I'm afraid that if they calibrate the combo to work well together that I will have issues when I put the lens on another body. I would like to use it with both my 7D and 6D.

I guess I could just live with the fact that it needs -18 MFA and just wait for the 7D Mark II or just get a 1D Mark IV, but for as much as I paid for this thing, I expect it to work perfect on whatever I put it on.

Any suggestions from anyone here who has experienced something like this before?

Here is a photo from yesterday after I got the MFA dialed in. This was from about 20ft shot wide open at F4 so I know I got it right. It just bothers me that it requires so much MFA to work. It's almost maxed out on MFA while other bodies need 0.

So what is the issue if it works fine with -18MA?

I wouldn't let the lens get adjusted, and frankly, I'm with Bobby, just let the MFA do it's thing.

Maybe it's a crop thing? Have you been able to put it on any other 1.6x crop bodies? Plus the lens will work best on your 1D and 6D anyways, giving you superior IQ. I'd not jeopardize that marriage so your 500m can sleep around with that strumpet 7D!

bobbyz wrote in post #15693847
So what is the issue if it works fine with -18MA?

Well for starters, it's not very consistent. -18 is close but sometimes it's more sometimes it's less. Also if you paid 6K for a lens would you be happy that it needed almost all the MFA your camera can provide just to sort of work ok?

As I already said, why is this only on happening on multiple 7D's and not on any other bodies that I've tried? Is there some sore of firmware update for the lens to make it work better on a 7D?

I thought it was consistent at -18MA. I have had old 500mm f4, never an issue with 1dmk2 which had no MA. On old 30d it was a bit off.

CyberDyneSystems wrote in post #15693912
I wouldn't let the lens get adjusted, and frankly, I'm with Bobby, just let the MFA do it's thing.

Maybe it's a crop thing? Have you been able to put it on any other 1.6x crop bodies? Plus the lens will work best on your 1D and 6D anyways, giving you superior IQ. I'd not jeopardize that marriage so your 500m can sleep around with that strumpet 7D!

Well, the whole reason for buying the 500 was to get as much reach as possible, which means using it on my 7D. Yes I know it's not technically reach but it is much more pixels on target. On the 6D I have to use an extender to sort of match what I get on the 7D without an extender. And we all know what extenders do to image quality.

No, after paying 6K I would not be happy either. But it does not sound like the lens is at fault.
If you send it to Canon with the 7D, I'd make sure that the Mk IV goes too.

CyberDyneSystems wrote in post #15693935
No, after paying 6K I would not be happy either. But it does not sound like the lens is at fault.
If you send it to Canon with the 7D, I'd make sure that the Mk IV goes too.

I don't personally own a Mark IV, the guy I bought it from does and I tried it with the lens to see if it had the same issue and it doesn't. I have a 7D and a 6D for now. Have been thinking of getting a Mark IV for a while though.

It just sucks cause I saved for over two years for this thing and I've lusted over it for longer than that, only to finally get one and it's not as perfect as I would have hoped.

Also to answer your previous question, I haven't tried it on any other crop camera.

If it works consistent then I wouldn't do anything. Only if different MA for different distances etc then send it in. It won't be cheap with insured shipping unless you local to canon service center. BTW - That lens need some stopping down. And get 1.4xTC if you don't. Here is at 700mm f8 with my old 30d.

Ahh, sorry, this makes your 7D issue much more pressing. My misunderstanding.
Yes, sounds like a trip to Canon might be in the works. If they tweek the 7D, you may need to MFA your other lenses afterwards.

I don't think they can 'tweak' the body, they just need the body to properly adjust the lens. It may or may not need MFA on the other bodies that it currently needs MFA on.

bobbyz wrote in post #15693958
.. BTW - That lens need some stopping down.

Wait, wait wait .. I know the landscape has changed a bit since the new IS II super telephotos were released, but up until 2009 or so the 500mm f/L IS was one of, if not the sharpest lens in Canon's stable.

It shoots happily wide open all day!

YES! And nice shot by the way!

bobbyz wrote in post #15693958
If it works consistent then I wouldn't do anything. Only if different MA for different distances etc then send it in. It won't be cheap with insured shipping unless you local to canon service center. BTW - That lens need some stopping down. And get 1.4xTC if you don't. Here is at 700mm f8 with my old 30d.

I'll play with it some more tomorrow but I think -18 is about as close as it gets. I do stop down usually to at least f5.0 or 5.6 if I have enough light. And I do have the 1.4x extender but I won't use it until I get the focus issue sorted out without an extender.

CyberDyneSystems wrote in post #15693960
Ahh, sorry, this makes your 7D issue much more pressing. My misunderstanding.
Yes, sounds like a trip to Canon might be in the works. If they tweek the 7D, you may need to MFA your other lenses afterwards.

That's what I was afraid of. So they would tweak the 7D and not the lens, correct?

ejenner wrote in post #15693966
I don't think they can 'tweak' the body, they just need the body to properly adjust the lens. It may or may not need MFA on the other bodies that it currently needs MFA on.

There is an adjustment for back/front focusing that can be done on bodies too.. this is what the MFA does for us on a per lens basis, but there is a master setting, if you will.


Here is how you can do it yourself on a "Pre MFA" body;

https://photography-on-the.net/forum/showthre​ad.php?t=345457

SVTmaniac wrote in post #15693968
That's what I was afraid of. So they would tweak the 7D and not the lens, correct?

Honestly, I don't know. But I would assume that if they found the 7D was out of spec, it would get adjusted. Strange it's the one lens on one hand, and the one body on the other. Really weird.