Canon EOS system focus issue - 50mm f/1.2L lens

Steven Lee · Dec 11, 2022

I just purchased a Canon EOS 1v. This was my dream camera when I was a teenager, and of course I could never afford it. By the time I graduated college and returned to photography, digital was all the rage and I've been happily shooting Canon DSLRs for many years.

Anyway, this beast shows up and I immediately exposed four rolls of Delta 400 with all EF lenses I have. One of them, the 50mm f/1.2L, is noticeably back-focusing. So much so that misfocus at anything at f/2 and wider is quite evident even on 4x6 prints (the far eye is in focus in head and shoulder portraits instead of the front eye).

My last DSLR (5D Mk4) had focus micro-adjustment feature, so I calibrated it to this lens. My question is: how do I adjust focusing on the EOS 1v? I went to Canon USA service web page, but they don't list this lens as something they work on.

Does anyone know how focus calibration works for film bodies? I am sure the body is absolutely fine, because it focuses exactly the same way as the digital body, it's just this one lens is off and I can't adjust for it. Whom should I send the camera (or lens? or both?) to? Googling is quite difficult because of pages and pages of youtube spam and 100% digital hits.

Thanks!

halfaman · Dec 11, 2022

Focus calibration is possible but needs special Canon software and hardware. Check service manual, AF adjustment starts in page 4-25.

https://learncamerarepair.com/downloads/pdf/canon-eos-1v-service-manual.pdf

Canon technical service is your best choice, otherwise it may be difficult to find somebody who has this equipment.

Steven Lee · Dec 11, 2022

@halfaman THANK YOU!!!

Steven Lee · Dec 11, 2022

Actually, going through the service manuals, looks like it's the lens that needs adjustment. The body only has a global adjustment which will apply to all lenses, and that's clearly not my case because only one out of five lenses has a problem. That's good news because it seems simpler and I may even attempt to DIY... Thanks again for reminding me of service manuals!

Duceman · Dec 11, 2022

Just to be clear, you've confirmed that it is only occurring with this lens and no other?

Steven Lee · Dec 11, 2022

@Duceman yes. I also have other EF-mount lenses, including the 85mm f/1.8 USM (quite shallow DOF also) and they focus well.

pkupcik · Dec 11, 2022

EOS-1V is beautiful camera, congratulations. I also use it with 50L 1.2, luckily don't have any focus issues, what a great camera+lens combo, photos look great and the gear as well . Hope you resolve your focus adjustment issue.

albada · Dec 11, 2022

That camera is auto-focus. So after the camera has focused the lens at the film-plane, it should be in focus, even if the infinity-calibration in the lens is off.
Auto-focus isn't perfect. I had an Elan II in the 1990s. As a test, outside in sun or shade, I first carefully manually focused a Tamron 28-200 lens, and then auto-focused it. To my disappointment, I watched the image become slightly out of focus in the the VF in real-time.

I suggest that you perform that experiment. If the manual focus is sharp and the auto-focus is soft, and you know AF is fine with other lenses, then say to yourself, "AF isn't perfect."

Mark

grat · Dec 11, 2022

Steven Lee said:
Actually, going through the service manuals, looks like it's the lens that needs adjustment.

Correct. You said you had to correct the focus on this lens on another body.

albada said:
That camera is auto-focus. So after the camera has focused the lens at the film-plane, it should be in focus, even if the infinity-calibration in the lens is off.
Auto-focus isn't perfect. I had an Elan II in the 1990s. As a test, outside in sun or shade, I first carefully manually focused a Tamron 28-200 lens, and then auto-focused it. To my disappointment, I watched the image become slightly out of focus in the the VF in real-time.

I don't pretend to know the details of the Canon AF system-- it is, however, very good, especially with Canon EF lenses. Legend has it that Canon has never licensed the EF protocol to any company-- so any company that uses it in their lenses is doing so by reverse engineering. On my EOS 5, my modern Canon EF lenses work just fine-- but my "modern" Sigma lenses which work well with my EOS 90D, have to hunt, and are occasionally a bit off on their focus on the EOS 5.

It's conceivable there's a bit of a distortion in the OP's lens over one of the AF points, or perhaps the position tracking in the lens isn't quite agreeing with the camera. It is known that some Canon EF lenses require slight adjustment to play well with some bodies, and newer Canon SLR's have a micro-focus adjustment for this purpose.

As you say, AF isn't perfect-- but Canon built their reputation in the 90's on their auto-focus being the best.

Cholentpot · Dec 11, 2022

The EF system as far as I can tell is as near perfect as you can get with autofocus.

Modern film with EF L series lenses never looked better. Shooting portraits with Tmax 100 and a 70-200 2.8L shows how very good film is in reality. I use my EOS 35mm cameras extensively. They're not as much fun as the older manual cameras I own, but when I NEED the shot I reach of an EOS.

Steven Lee · Dec 11, 2022

albada said:
That camera is auto-focus. So after the camera has focused the lens at the film-plane, it should be in focus, even if the infinity-calibration in the lens is off.
Auto-focus isn't perfect. I had an Elan II in the 1990s. As a test, outside in sun or shade, I first carefully manually focused a Tamron 28-200 lens, and then auto-focused it. To my disappointment, I watched the image become slightly out of focus in the the VF in real-time.

I suggest that you perform that experiment. If the manual focus is sharp and the auto-focus is soft, and you know AF is fine with other lenses, then say to yourself, "AF isn't perfect."

Mark

Mark, I do not want the AF on this lens to be perfect, I only want it to be just as good as my other EF lenses.

gone · Dec 12, 2022

But if this focus error only occurs w/ one lens and not the others, doesn't that point to a problem w/ that one lens and not the camera? Or did I miss something?

Cholentpot · Dec 12, 2022

momus said:
But if this focus error only occurs w/ one lens and not the others, doesn't that point to a problem w/ that one lens and not the camera? Or did I miss something?

You've missed nothing. Here, sit down and have a juice box and cookies.

film_man · Dec 12, 2022

The 50/1.2 L has focus shift, you can probably get it adjusted to a point but it is part of the lens design and happens at certain apertures (f/2-2.8) and is more pronounced at certain distances (close-up). Which of course is crazy as that is where you'd use it most. But it is what it is, look it up if you want. Canon can probably adjust the lens a bit but it will only make it front-focus at this stop and back focus at that stop etc etc. You'd have to send both the lens AND camera to get it done properly. The camera cannot be adjusted for a specific lens, as already said.

MattKing · Dec 12, 2022

Thread title tweaked

Steven Lee · Dec 12, 2022

@film_man that's great to know, thank you.

Canon EOS system focus issue - 50mm f/1.2L lens

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