Canon 50 1.2L ...Bad copy?

So I have never had this happen before, but I have never shot 1.2 either, but I feel the new 50mm 1.2L is defective. Is it THAT hard to nail focus with? I could understand focus/recompose being a trick to master? But I am not doing that. I am having issues getting focus even at center focus point only and not moving the camera.
Here is what I am doing:
Focus on a small light switch of a lamp at 4'. Then taking a picture. Focus on the shade about 12" infront of it, then focusing back to the switch and taking a picture...focus on shade, focus on switch and take a picture.
Not kidding, 50% of the images are totally blown focus.
I am sitting on a sofa, I feel humbled. But I also question how it can be me.

If there is an issue, it would be with your camera. Your camera tells the lens where to focus. Do you have the camera on AI Servo or One Shot? That is about the only question I could come up with.

TeamSpeed wrote in post #17896219
If there is an issue, it would be with your camera. Your camera tells the lens where to focus. Do you have the camera on AI Servo or One Shot? That is about the only question I could come up with.

I almost wonder if it was just sticky? I put it in one shot and it seemed to have gone away, so a light went off maybe it's adjusting right at the last moment, but I went back to servo and I am seeming to nail them now.
I just did about 100 shots of focus/focus/shoot and am nailing a very high percentage now.
The 6D might be getting replaced asap lol, I cannot see the limited focus points working too well with this wide open. Have to scope out an overlay of a MarkIII focus point layout over 6D.

what happens when you stand 8' away from the subject instead of 4'?

I have the same combo as you, at short distances the lens is softer and the DoF is tiny, even your breathing will move your point of focus. To do a proper test you need to setup a tripod and focus on something that is not moving. Mine had a slight back focus, but the focus is just fine after the micro adjusting. Also the focus shift is very slight in mine. I tested mine at MFD and also at about 5 feet. I would set the lens to infinity and let it find focus, doing this 3 times (to get an average focus feeling) while micro adjusting.

I will test that further distance and get a focus chart later today or tomorrow when I have some time.

Depending on the quality of light and the subject's inherent contrast and detail, the camera's AF may not exactly hit where you are wanting it to. And, if the target is small it may also throw the AF off.

Basically, some subjects shoot better than others. Do you have photos of this lamp switch? How is the lens when it comes to shooting other objects?

Not a ton of dof at 1.2 either.

This is the setup I was using. Nothing fancy. The ruler is set on an incline to better evaluate the DoF area. The robot figure is about 8 inches tall. I was about 4 feet away. The closer one is just a crop of the same image. The 5cm mark on the ruler was at the same level as the sticker on the box. Jpg's SOOC. My camera is set to zero sharpening. Usually it is recommended a distance of about 25 times the focal length, in this case about. 4 feet.

Here's what I do
decide on the distance you intend to use the lens the most
use a tripod and set up your target
manually focus using live view (this is to get your base line for sharpness at F1.2)
set up AAA batteries staggered and do your testing.
I find that color/temperature of the light will effect the AF
The 50L at F1.2 gives an ethereal effect IMO.

I found the ruler more helpful than the batteries, (in the pictures I increased the distance to get more of a feel for the DoF fall off) but, the idea of getting a baseline liveview shot sounds very good, I will try it as well.

Your lens is most likely fine. There are a couple of things that could be happening here.

Firstly, it's important to understand that phase-detect autofocus, the kind of AF you have in normal shooting (not live view) is optimized to get a decent focus lock quickly. It's not super precise, so with an f/1.2 lens you are going to have focus misses if you're taking shots at f/1.2, especially in anything less than ideal conditions with good light and a nice contrasty-edged target. The AF system has to "look" through the lens, so it's going to be even less accurate with a lens that is soft wide open. Zoomed-in live-view AF is going to be much slower, but more accurate.

Secondly, your lens body combination may need micro-focus adjustment. It's not uncommon for a fast lens like this to not be perfectly spot on. With slower lenses, the increased DoF usually has you covered. Not so at f/1.2. There are Youtube tutorials that show you how to do MFA, it's a slow, painstaking process that requires a lot of test shots in order to differentiate lack of precision from lack of accuracy. It's critical to understand the difference between precision and accuracy to take and interpret the measurements properly, Google it if you're unsure. MFA can only correct accuracy; i.e. a consistent tendency to front or back focus, it won't help with a lack of precision that is inherent with phase-detect AF and a fast lens. This is why you need to take a statistically-significant number of test shots when MFA'ing a fast prime.

Thirdly, hand movement. Even a slight sway or twitch between AF lock and shutter release can move the focus point. Tests have to be done on a tripod, as windpig outlined.

Fourthly, the center AF point is potentially larger and not perfectly aligned with the etching you see on the focus screen. If you're focusing on a tiny detail in complex 3-dimensional scene, the AF system might be focusing a little bit in any direction from where you think it is. Just something to keep in mind.

I love this lens and I would not be without it. But I almost never recommend anybody else get one! I warn people that the learning curve for this thing is tough. It is slow to AF by design. It has to be accurate so fast AF isn't going to happen.
As with any lens, however, you may need some focus adjustment. You need a real focus target instead of a few objects.

The only other lens that comes close to this lens is its big brother the ef 85mm f1.2L. I love it to as there is nothing like f1.2.

ebiggs wrote in post #17900421
I love this lens and I would not be without it. But I almost never recommend anybody else get one! I warn people that the learning curve for this thing is tough. It is slow to AF by design. It has to be accurate so fast AF isn't going to happen.
As with any lens, however, you may need some focus adjustment. You need a real focus target instead of a few objects.

The only other lens that comes close to this lens is its big brother the ef 85mm f1.2L. I love it to as there is nothing like f1.2.

Agree with all of this. I love my 50L dearly, but it has been the most difficult lens I've ever owned in terms of learning curve and repeatable results. I use it in AI Servo quite a bit with back button focus. One of the earlier comments about even breathing having an effect is true.

Which lens do you like using more ebiggs? The 50 or the 85?