# 5D3 + 50 F1.2 L



## mingyuansung (Dec 29, 2012)

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?


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## Dylan777 (Dec 30, 2012)

mingyuansung said:


> 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.


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## mingyuansung (Dec 30, 2012)

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.


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## Plato the Wise (Dec 30, 2012)

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.


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## mingyuansung (Dec 30, 2012)

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.


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## DigiAngel (Dec 30, 2012)

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.


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## mingyuansung (Dec 30, 2012)

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


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## DigiAngel (Dec 30, 2012)

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.


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## Martin (Dec 30, 2012)

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.


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## cdang (Dec 30, 2012)

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.


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## CharlieB (Dec 30, 2012)

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.


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## mingyuansung (Dec 31, 2012)

cdang said:


> 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.


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## cdang (Feb 23, 2013)

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.


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## mingyuansung (Feb 23, 2013)

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.


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## Menace (Feb 23, 2013)

mingyuansung said:


> 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


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## Mt Spokane Photography (Feb 24, 2013)

The 50L is a pretty special lens. You can run into issues with focus shift at close distances when you shoot stopped down. I'd put it on a tripod at 8-10 ft, and try shooting a brick wall at f/1.2 (Camera carefully aligned) using the different focus points. This eliminates problens like focus shift, so you see the AF performance. Do not stop the lens down, check it at 1.2!

Take 10 shots at each point resetting the lens to infinity each time. If the outside points are oof, I'd return it either for exchange, send camera and lens to Canon or try a different lens.


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## 7enderbender (Feb 26, 2013)

I use mine with a 5dII - which supposedly has "horrible" AF compared to it successor. And yes, "front focus" is part of the lens design. As far as I know that hasn't really bothered people too much for the last 80 or 100 years or however long this optic formula has been used now.
AF is never 100% since it is focusing on something that has enough contrast that falls in the area of the focus point - which I believe are bigger than the little dots you see in the viewfinder. So results vary since the camera can't read our mind quite yet. And slight movements will have an impact also.
What I'm saying is: if you're already obsessing about "sharpness" of the lens you might consider just returning it for something different that you like better. Maybe something is really out of whack with either the lens or the body. Maybe try another one and also another body and see if there's a noticeable difference under real life circumstances.
If you can get over it shoot it wide open and enjoy the colors and contrast which is probably second best to the Leica/50mm combo.


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## RLPhoto (Feb 26, 2013)

I've noticed after using the 50L for awhile now that it has a field curvature outside the center point. My solution is multiple shots while slightly moving forward or if you focus and recompose it seems that it lands pretty close as well. 

Then sometimes, the AF just nails it. The 50L is a fickle and unique beast, it just takes practice to learn it quirks.


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## RS2021 (Feb 26, 2013)

RLPhoto said:


> I've noticed after using the 50L for awhile now that it has a field curvature outside the center point.



Exactly...that is the crux of 50L issues and strengths.... That "dreamy" look is the product of that curved focal plane...so using a centerpoint AF and recomposing is a fool's errand with this lens. Superimposed on this is the real focus shift issue which canon can address but again only to a point if they want to keep the optical formula simple, weight and price down.

85L II, a close cousin, also released the same year as the 50L, side steps this if only marginally...Being of longer focal length 85mm already has the advantage of some image compression at the focal plane...residual curvature can be "corrected" by additional glass designed to provide a more flat field, and I would hazard a guess this is the case for 85L II. 

Could explain the massive size and weight we see with 85L II...not to mention the price.

You get the 50L because you know its strengths and draw backs ... in other words, it is what it is.


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## kbmelb (Feb 26, 2013)

That is par for the 50L course. The focal plane is definitely curved. I also found the 50 1.4's focal plane to also be curved though.

I AFMA to the outer points (second from last column) since I never use the center point for focusing.
I have extremely good results.

The 50L is far from perfect but when you get it to work for you, the results are stunning.


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## RS2021 (Feb 26, 2013)

I no longer own the 50L but when it was in my stable, the simplest solution that worked for me was to step back just a bit from the subject.

I know this is annoying creatively, but this invariably produces more consistent AF with the 50L. 

If 50L is your lens of choice, you just have to work around its quirks and deal with it on its own terms.


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## THX723 (Feb 26, 2013)

Folks, the 50L focal plane isn't curved or anymore curved than the average lens.

Imagine taking a single picture of a _flat _poster on a wall (for exaggeration, this could be f/1.2 at close range), do you suppose the picture is out of focus away from the center? The answer is no. That was field curvature, or the lack of, in a nutshell.

The subject of focus variance using different focus points (wrt other points) has everything to do with the excessive spherical aberration (SA) inherent to the 50L's optics. While this _designed_ SA is great for its artistry, it is problematic for any phase-detect type auto-focusing systems. This same under-corrected SA is also responsible for the infamous focus shift.


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## RS2021 (Feb 26, 2013)

THX723 said:


> Folks, the 50L focal plane isn't curved or anymore curved than the average lens.
> 
> Imagine taking a single picture of a _flat _poster on a wall (for exaggeration, this could be f/1.2 at close range), do you suppose the picture is out of focus away from the center? The answer is no. That was field curvature, or the lack of, in a nutshell.



I disagree. True, SA, CA, and coma all constitute aberrations, yes...but what the lay-person refers to as "curved focal plane" while not technically or semantically precise, is nonetheless not an imagined phenomenon. Petzval field curvature does exist.

Taking SA as an example, imagine if the points in sharp focus can be joined in a 3D graph across the "focal 3D space" and your sensor can be magically bent to precisely pass through these points of maximal focus... It will not be a flat plane...while one could hope for a nice smooth bowl like graph, some complex optical systems, at least in theory, could generate nice central plane with concentric ripple with circular throughs and waves around this plane.

The challenge for optics designers is to address/correct SA, CA, coma and other spurious aberrations and distortions that arise in multi-element optics in a fair compromise and yet keep price and weight down...I do however agree that some SA was intentionally incorporated into the f/1.2 systems for artistic effect.

But field curvature does exist and is in fact the norm, to varying extent in both corrected and uncorrected optical systems. 

So when the fanboys want corner-to-corner sharpness in the f/1.2 systems with zero CA and that melting bokeh, one has to just smile and be nice


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## kbmelb (Feb 27, 2013)

THX723 said:


> Folks, the 50L focal plane isn't curved or anymore curved than the average lens.



Apologize. I shouldn't have said focal plane. I'm not a techie. I guess I was referring to the field curvature. I just know that if you lock focus with the center point and recompose you will more than likely end up with an image that is at least slightly out of focus.


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## THX723 (Feb 27, 2013)

Ray2021 said:


> I disagree. True, SA, CA, and coma all constitute aberrations, yes...but what the lay-person refers to as "curved focal plane" while not technically or semantically precise, is nonetheless not an imagined phenomenon. Petzval field curvature does exist.
> 
> Taking SA as an example, imagine if the points in sharp focus can be joined in a 3D graph across the "focal 3D space" and your sensor can be magically bent to precisely pass through these points of maximal focus... It will not be a flat plane...while one could hope for a nice smooth bowl like graph, some complex optical systems, at least in theory, could generate nice central plane with concentric ripple with circular throughs and waves around this plane.
> 
> ...



Of course there will always be some _however measurable _ curvature to the focal plane in the real world. Is the Earth truly round? Is a flat wall ever truly _flat_?

It was that very reason I took the time to qualified with *"the 50L focal plane isn't curved or anymore curved than the average lens."* For the intent and purpose, the focal plane of the 50L is not abnormally nor excessively curved. In layman's term, it’s flat or of no real concern.

Spherical Aberration is not remotely the same as Chromatic Aberration nor does it have anything to do with focal plane curvature. It does however have everything to do with the shape/curvature of the spherical lens and can be corrected by way of aspherical contouring and/or counter elements (e.g. floating element).

The phenomenon of front focusing with the peripheral AF points is an entirely different matter and surely isn't called Focal Plane Curvature. Instead what was observed is none other than misjudgment by the phase-detect AF system in the presence of excessive Spherical Aberration. Despite such flaw, each peripheral AF points are still able to arrived at a given focus plane (even if not actually in-focus), but more importantly, be uniformly out-of-focus (aka flat).

On the other hand, given a lens that _does_ exhibit significant Focal Plane Curvature, one would be able to achieve perfect focus at any AF points (including peripherals), but the image would not be uniformly in-focus (only area near the center of focus). This phenomenon is independent of the type of focusing system used btw; AF or Manual. No amount of eye-balling MF will ever get you a flat pic. Clearly not what's going on here. We know the 50L is fully capable, especially MF'd or even Live-View contrast AF’d.

So what is it about SA that sends phase-detect AF to the funny farm?

Imagine at any given point on the actual in-focus plane, there exists a series of also in-focus points in-front and/or behind it (projected from different parts of the lens. see illustration). A typical phase-detection AF system simply doesn't have the smarts to make that judgment call. In a way, it did what it was designed to do, just didn't lock-on to the best one. This same mechanism is also the reason for Focus Shift at all AF points (even the center).

By stopping down (pinching of the aperture), you can cut down on the number of these false positives projections; less interference. For the 50L, the cut-off is somewhere around f/5.6-8.0 (DOF is large enough by then, that it’s tough to say for sure).

The bottom of the line is Canon had made a conscious decision to leave excessive (not little, but a lot) amount of SA uncorrected. Call it for the artistry or what have you, it’s there and it’s real – a real pain in the arse … until one learns to cope with it.

Through the ownership of the 50L, I have come to leverage the peripheral AF error against the center point focus shift. 

AFMA wrt the center point is assumed. Focus shift at the center is some degree of back-focus when in the red-zone *(within a several feet of subject, and f/1.2 > aperture > f/5.6)*. Knowing that switching from center to the peripheral points would result in some degree of front-focus, it could be used to negate the back-focus (from the focus shift). Examples:


At wide open (f/1.2) I know I can shoot fairly reliable without thinking much.
Inside the red-zone, I select one of the peripheral AF points best for the given aperture (you’ll have do some test runs for yourself to determine which pairs well).
Outside of the red-zone, I shoot normally (any F-stop with any AF points).


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## THX723 (Feb 27, 2013)

kbmelb said:


> THX723 said:
> 
> 
> > Folks, the 50L focal plane isn't curved or anymore curved than the average lens.
> ...


No apology. Field Curvature and Focal Plane Curvature are of the same btw. See my response above.


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## RS2021 (Feb 27, 2013)

@THX723... You take grouped terms I used in one context and twist them out of context to make your arguments...

It will take too long to refute or agree with individual items point by point...and that will result in even longer paragraphs from you... So I am going to wish you well and move on. Cheers!


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## Daniel Flather (Feb 27, 2013)

Shoot at f1.2, open the file in DPP, hit command J (I don't what it is for windows), look at the size of the focus point relative to the subject it covered. Most of the time (for my images) the DOF is thiner than the AF point!


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