How much faster is a 85mm 1.2L II on a 5D Mark III vs Mark II?

Question, how much faster is the 85mm 1.2L II on the 5D Mark III comparing to the 5D Mark II?

I'm having a hard time justifying the cost of a 5D Mark III + Grip (almost 2K more after selling my 5D Mark II + Grip here in Canada).

I already know I will be upgrading to the 85mm 1.2L II, I find that my Sigma 85mm 1.4 is just too inaccurate when focusing,

The 2 things I notice are:
A) It's slow on anything but it's center-cross AF Point when using my Sigma 85mm 1.4, it'll struggle to get a lock on anything but bright conditions.
B) I constantly feel like I have to under-expose in AV/TV mode by about 1/3 stop or 2/3 stop's, this could be myself as I like pictures to be a bit more contrasty and punchy, but it's worth noting anyways.

I know upgrading to the 85mm 1.2 L II will most likely get rid of my inaccuracy issues but I'm worried it will still struggle and take FOREVER to get a lock. Do I have to upgrade to a 5D Mark III to alleviate this issue?

Notes:
- Please don't tell me that using a 1.2/1.4 aperture is very shallow which could be why I get inaccurate shots, I do know that already! I am conscious about it whenever I shoot.
- I own the EG-S focusing screen on my 5D Mark II which helps me tremendously for depicting DOF, I see that there is no such thing on the 5D Mark III and that many users do NOT like this about it and there is no solution so far.

Because of being able to autofocus decently just at the center, was the reason why I upgraded to the 5D Mark III. Now I'm getting excellent results shooting my kids with the 85L while running.
Also, you will be able to microadjust for wide and tele for your zoom lenses. I loved my MarkII, but the Mark III is incredible.

If that is the plan, than first upgrade to the 85L.
That should solve about half your problems.

Then if you are unhappy with your 5D2, upgrade it.

The 5D3 has a much better AF system, but it really depends what you are shooting. Low light, moving subjects, that will make the 5D3 a better option. Based only on the lens, its hard to say.

Strangely people are one by one discovering that 85L1.2II always had a fast and accurate AF ... Ther is like a 5DMKIII mood ...
Like him http://www.ronmartblog​.com …oes-5d-mark-iii-make.html or him http://diglloyd.com …5DM3-Canon85f1_2L_II.html

But I am using for years 85L for fast sport or erratic action with a 5DMKII and 1DMKIII. My own experience is that 85L has never changed and it's one of the most accurate AF I am using.
But, I imagine people were not trained or just skilled enough to be able to point and track accurately on a subject's eyes, they also can't choose the proper distance or aperture to shoot any action or sport to get both eyes and nose in DOF.
Maybe, 5DMKIII and 1Dx just give some more margin for outer focus points ? but 1DMKIII already could focus with any AF points a fast moving subject.

I am surprised that you are having issues with a lens as fast as f/1.2. I use a 100-400 f/4-5.6L on my 5D2 and have had no issues. I press the shutter release half way - it focuses. Full stop, end of story, each and every time without fail. Thats using One-stop or AI Servo.

So is it caused by low light issues such as contrast (a lack of) rather than AF problems with the lens and body maybe?

Lowner wrote in post #14852115
I am surprised that you are having issues with a lens as fast as f/1.2. I use a 100-400 f/4-5.6L on my 5D2 and have had no issues. I press the shutter release half way - it focuses. Full stop, end of story, each and every time without fail. Thats using One-stop or AI Servo.

So is it caused by low light issues such as contrast (a lack of) rather than AF problems with the lens and body maybe?

The "Canonball" is known for not being the fastest-focusing lens in the lineup. The non L 85mm f/1.8 is leaps and bounds faster to focus than the 85L, for example.

ceremus wrote in post #14852154
The "Canonball" is known for not being the fastest-focusing lens in the lineup. The non L 85mm f/1.8 is leaps and bounds faster to focus than the 85L, for example.

That's just an urban legend ! .. That lens is as fast as any other L lenses in a normal action/sport range. It's normally slower in a macro like DOF range (distance between 90cm to 2 meters) ... focusing system is not linear and clever to adapt to the DOF range situation, that's all.

Sorry, when I read from multiple reputable sources that the 1.2 is slower to lock focus than other lenses, I'm going to take them at their word.

I don't do sports, I suppose I do small walks when models walk away but nothing intense, I never use AI Servo though, I believe I stated my purposes which is really for Portraitures, Fashion photography and use with Strobe lighting.

Mine doesn't hunt, ever. From infinity, it takes a second to focus sure, but it always locks. Certainly not as slow as everyone makes it out to be (sometimes I swear people make it sound like it takes 5 seconds), its all a matter of opinion and tolerance. I've used mine to shoot dogs running - towards me, not parallel, and its kept up fine with all shots being keepers, with the 5D3.

I went to my local photography store and put the Sigma 85mm 1.4 on it and it worked perfectly. Going to have to upgrade.

ceremus wrote in post #14852292
Sorry, when I read from multiple reputable sources that the 1.2 is slower to lock focus than other lenses, I'm going to take them at their word.

Not all .... ..People who really tried that lens for action are thinking it has always been fast and accurate enough for any sports.

But "some" are discovery such feature with 5DMKIII or 1Dx http://www.ronmartblog​.com …oes-5d-mark-iii-make.html
and
He made intensive AF test in low light conditions .. http://diglloyd.com …5DM3-Canon85f1_2L_II.html
I don't think Canon made any change on 85L these last years they probably just never tried to get skilled enough before.. with 1DMKIII, like many other in this forum, I never found any limits with 85L, and just a bit more tricky with 5DMKII on outer focus points..

and I already made tons of shooting these last years in real life way ..
https://photography-on-the.net …hp?p=13163469&p​ostcount=4
I never got better results with a 70-200/4, 300L2.8/ 135L2.0 ..