5D3 + 50 F1.2 L

[mingyuansung]

Just bought 50L f1.2.  Mount on my 5D3, the center focus point is accurate from f1.2 throughout the range and all distance. However the left most, right most, top most and bottom most cross point are all front focus.  Is there anyone has experience that if Canon Service Center (Irvine, CA) can help adjust the 5D3 internal computer to make those 4 out side cross points focus accurately? Or I'd better return the lens within 30 days and forget about 50L? I called them and they say that they can help but no guarantee. That sounds to me "why bother the effort". Any suggestion?

[Dylan777]

Just bought 50L f1.2.  Mount on my 5D3, the center focus point is accurate from f1.2 throughout the range and all distance. However the left most, right most, top most and bottom most cross point are all front focus.  Is there anyone has experience that if Canon Service Center (Irvine, CA) can help adjust the 5D3 internal computer to make those 4 out side cross points focus accurately? Or I'd better return the lens within 30 days and forget about 50L? I called them and they say that they can help but no guarantee. That sounds to me "why bother the effort". Any suggestion?

I'm in Fountain Valley(Brookhurst & Warner), Near Fry's Electronics.

Never hurt to ask if Canon Service Center can help or not when you don't have the tool for this task. I doubt I would charge you for this service, since you still under 1yr warranty.

Front or back focus can be adjusted with Reikan FoCal - in your case, select Multi AF points mode.

I tried 4 copies from Crutchfield and all 4 have back focus issue. Out of 4, the sharpest lens was just above 800 @ f1.2 EV10plus (-1 AFMA on copy). Others were around 760-780 with -6 to -8AFMA.

I also ran my 50L from 1.4 to 5.6 through FoCal, I wrote down the AFMA values on a small note and I taped that note onto the lens hood. I'm not sure if I ever need smaller apertures f2.8 - 5.6 on f1.2 lens, but the AFMA values are there when I need it.

[mingyuansung]

I called them already. When Canon service center said I can send in my camera and lens, yet they do not guarantee to adjust those 4 focus point to be accurate since the center point is accurate. Then give me a lot of story like this is the nature of big aperture lens, etc. etc. When they say that, I really doubt if I should spend the time to try them. I live in San Diego. My 2nd copy will arrive in 3 days from Adorama. I will try the 2nd one. Then the service center maybe, then the Reikan FoCal as you suggested. Then maybe return it after all. It is hard. Thanks a lot for you sharing.

[Plato the Wise]

I have a 5DM3 and the 50L.

At f1.2 and close distances - say a half meter - the depth of field is less than 5mm! Even if you do get the AF dead on, you and or your subject will more than likely move enough to throw off the focus.

It's a futile effort.

Just to put this into perspective. I have shot tight portraits where one eye is in focus - but the eyelashes are not.

I have heard of many people on this forum sending 3 or 4 copies of the 50L and the 80L back to try and find one that focuses perfectly. These are just very specialized lenses. Most folks just don't understand their purpose and the mechanical tolerances involved.

[mingyuansung]

Yes. Thank you for you experience. My situation is, at the same aperture (f1.2 through f2.0), same distance (1m through 4m), the center focus point is always dead on. But the other 4 out most points (top, right, left, bottom most) will front focus if I use them. Not focus on eye but nose will be out of DOF issue. I understand that. I mean if I use right most cross point to focus, that point will front focus shift. I am sorry if I did not write it clear.

That will give me problem to do one time micro adjustment. I have to change adjustment value depend on the focus point used every time. Or always use center point focus and try to recompose. I am just wondering if anyone ever run into this situation and if Canon can fix this situation. I will maybe try Canon Service Center and report back. Or I will just use center point. Really hate to give up on it.

[DigiAngel]

that problem is known across the internet and it seems theres no solution for it. flaw in the lens design. just dont use the outer focus points in situations where you know it will front focus. every workaround you try will open another problem and is very time-consuming.

the only way of solving it would be a firmware change by canon that implements focus corrections depending on focus-distance and choosen autofocus-sensor.

[mingyuansung]

Yes DigiAngel. I think a firmware change is the ultimate solution. Thank you.

[DigiAngel]

the question is: can Canon provide one? I dont think so, as far as i know, they only calibrate camera and lens with the center focus point on a fixed distance. that wouldnt solve the issue.

[Martin]

Did you check if this is a lens decentralization or a body (AF sensors) issue ? Might be one of them. I would definitely check other lens . I had a problem with 35L which were not properly aligned inside.

[cdang]

I had the exact same experience with that combo. Only the centre points nailed focus every time. Ran it through Reikan Focal and manually made sure with the Sypder Lenscal and it was perfect with the middle points. But as you go to use the outer points, it's badly OOF. I got so fed up I was shooting F2.8 and smaller every time I used the outer points. In the end, I just got rid of it. Weird because my 50 1.4 was perfect. I hear someone mentioned field curvature but I don't know if it was this lens they were referring to.

[CharlieB]

Not sure what the cause of the issue is.

Some things to consider -

Focus system alignment, or rather, misalignment, would not give you front focusing on all the peripheral points.  That is, misalignment, with a good center, would give a combination of front and back focusing.

De-centering usually gives one edge focused, the other edge not.

Curvature of field is an interesting issue.  Not sure if most folks fully realize that film cameras do not hold the film flat.  Film itself has a curvature, and various means were used, beyond a simple pressure plate, to try to hold it flat.  I did extensive testing in the latter part of the 1970's with Nikon F2 cameras and film flatness.  In those cameras, when the pressure plate was upon negative film, the center of the film was about .0025 removed from the plate.  The film touched the plate about 1/3 out toward the edges, then gradually sloped away from the plate again toward the extreme edges.   The shape was sort of a M shape (or W).  It was assumed that camera lens manufacturers left some residual curvature of field intact, in order to actually improve imaging.  I was able to observe that curvature when setting up the focusing systems in those cameras (a real pain in the butt and then some!), which were adjustable in almost ever imaginable way to assure near 100 percent coverage, and perfect focus on any area of the screen (or as perfect as film/lens combinations would allow).   

What I'm saying is... knowing film IS NOT flat, and that sensors ARE flat... makes for interesting relationships in hardware.

[mingyuansung]

I had the exact same experience with that combo. Only the centre points nailed focus every time. Ran it through Reikan Focal and manually made sure with the Sypder Lenscal and it was perfect with the middle points. But as you go to use the outer points, it's badly OOF. I got so fed up I was shooting F2.8 and smaller every time I used the outer points. In the end, I just got rid of it. Weird because my 50 1.4 was perfect. I hear someone mentioned field curvature but I don't know if it was this lens they were referring to.

Yes. My 50 1.4 is perfect all 5 focus points (center, top, bottom, left, right). My 24-70L II, 100 f2.8 L are also perfect with all 5 points. Only this 50L.

I called Canon Service center at Irvine, CA with my CPS membership number. The guy there told me that 5d3 has adjusted for 50L outside focus point in order to fix the famous back focus issue. I can send in my camera and lens and they can take a look the outside focus points yet no guarantee to fix it. I also confirmed with another forum that some people there have the same issue with center focus point perfect on 50L but blurring using other focus points. It also happens to 85L. It really depends on if your 50L has back focus on older camera model, it will be all accurate on 5D3. If your 50L is perfect, you will get inaccurate focus because of this adjustment the other forum concluded. I have no other camera to verify this experience though.

I know 50L has design issue and researched a lot on the net before I purchase it. Many people report 50L works well with their 5D3. And that is the reason I really want to test y luck and I thought 5D3 fixed the issue.  Honestly, I would just use center focus point and crop. 

BTW, Canon service center also told me the adjustment will be in 5D3 and for specific lens only. It will not affect other lens I have. I will report back if I decided to try their service center or not.  Thanks a lot for everyone sharing your experience.

[cdang]

Have you tried sending it to canon yet ? I seem to have the same problem with all my fast prime lenses though not as bad as the 50L. It exhibits similar behaviour with my 85L and 200L. I think I will send the camera and lenses to canon and keep my fingers cross.

[mingyuansung]

I have not send them in... Please let me know your result.  I have one year to do it though.  Just can not find time to go there yet.  And I am afraid they will mess up my other lens. By the way, I just bought 35L.  I want to try if 35L works fine, I may just sell the 50L. Thanks.

[Menace]

I have not send them in... Please let me know your result.  I have one year to do it though.  Just can not find time to go there yet.  And I am afraid they will mess up my other lens. By the way, I just bought 35L.  I want to try if 35L works fine, I may just sell the 50L. Thanks.

I've used both and like them both. Do try the 35L as I think you be really satisfied with it.

Cheers