My RF 70-200 f2.8 is front focusing

Started Dec 3, 2019 | Discussions thread
OP R5D4 Contributing Member • Posts: 893
It's back from Canon, and still front focuses

Got the lens back from Canon today. Despite Canon claiming the lens is 100% "zeroed" at all focal lengths and focal distances and working perfectly, the problem is in fact still there, and nothing has changed.

First, about the firmware. I sent it off with 1.0.3, which was current last week. Upon receiving it today, I checked the firmware and they did not update it. (that seems odd, no?) So I tested it both before updating and after updating to 1.0.5. The firmware made absolutely no difference.

Then with the lens at MFD, I ran it through 200mm, 135mm, 100mm and 70mm, with identical results to those I got a week ago. I took about 10 shots for each length, and every single frame was identical. The lens front focuses at its worst at about 3mm at 200mm, and gets gradually better as you zoom out to 70mm. The images below are all hand-cropped to best show numbers on the chart. All shots are at f/2.8, IS off, and shot in servo mode and 1-point AF (small box). The focus is centered well within the QR code, and I used a sturdy tripod and a bluetooth remote.

200mm MFD

135mm MFD

100mm MFD

70mm MFD

Notice at 70mm it looks fine.

I then back up as much space as I had in my test area, which is 7 feet. The front focus is noticeable at this distance too at 200mm.

200mm at 7 feet

At several points I switched to manual focus. The tick marks were always off a bit of the confirmed focus point. With 10x zoom I could dial in critical focus (this focus ring is so sensitive that it only takes about a mm of movement of the ring to correct the focus)

As another user described here, you could almost describe the intended focus area as at or just beyond the edge of the depth of field. When I look at the picture of the eye I posted in the OP, the depth of field NEARLY reaches the pupil, but instead starts with the eyelash and encompasses the eyebrow.

I took a lot of pictures of mundane objects and the ones I will post here are of a map I have hanging on the wall. I used a tripod and first did AF then MF. Again, multiple shots 100% repeatable.

Auto Focus MFD @200mm

Manual Focus MFD @200mm

I think the results speak for themselves.

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