70-200mm f2.8L IS

James Miller · October 4th, 2009, 10:19 AM

Hi, Just bought a Canon 70-200mm f2.8L IS and noticed when I zoom full at 200mm to focus and then pull back out to frame I loose focus.

I have to turn a couple of millimeters to refocus, that kind of defeats the purpose of zooming to focus.

I assume this is a back focus type issue? Is this a fault or a characteristic of the lens.
Can anyone confirm this.

Thanks, James

James Miller · October 4th, 2009, 11:34 AM

Quick update, I have found that at any zoom range once focused sharp, there seems to be a bit of free play on the zoom ring.

One side of the free play is sharp the other soft, free play travel is about 1.5mm. My other zooms have a bit of freeplay in the zoom ring but it does not change the focus.

Now I found this freeplay I can zoom to 200 focus then pull to 70 twist the freeplay and it is sharp. This must be a defect.

Paid a quick trip back to 'Park Cameras' and they had no more units in, they sold 4 yesterday. 7-10 days for restock.

A young chap had a quick look and agree it was a problem, he only tested it for a couple of seconds and I'm not sure if he was just agreeing with the customer.

He told me to use it until they had restock, so I brought it home.

Model number UX0918 - September / 2009

Don Miller · October 4th, 2009, 12:09 PM

here's a list of parafocal lenses:

Parfocality - Canon sez: Canon SLR Lens Talk Forum: Digital Photography Review

note this is from 2004

James Miller · October 4th, 2009, 12:34 PM

Thanks Don, So it is apparently Parafocal.

It's the free play that seems to be an issue, wish I had another to test. Should have gone with the f4 or the Sigma!

Evan Donn · October 4th, 2009, 01:32 PM

Quote:

Originally Posted by James Miller

I have to turn a couple of millimeters to refocus, that kind of defeats the purpose of zooming to focus.

This worried me at first because so many still zooms are not parfocal, but I've found I don't miss it much - instead of zooming with the lens you just use the camera's zoom function and it works just as well.

James Miller · October 4th, 2009, 02:06 PM

Evan, I didn't notice at first because it focuses so well by hand live. It's only when I was trying to get a handle on it's limits on legs I noticed it.

I just find I automatically zoom in to focus. If it like this on another copy, I'll just have to treat her like a prime.

October 4th, 2009, 10:19 AM	#1
James Miller Major Player Join Date: Mar 2007 Location: Sussex, UK Posts: 317	70-200mm f2.8L IS - Focus Problem? Hi, Just bought a Canon 70-200mm f2.8L IS and noticed when I zoom full at 200mm to focus and then pull back out to frame I loose focus. I have to turn a couple of millimeters to refocus, that kind of defeats the purpose of zooming to focus. I assume this is a back focus type issue? Is this a fault or a characteristic of the lens. Can anyone confirm this. Thanks, James

October 4th, 2009, 11:34 AM	#2
James Miller Major Player Join Date: Mar 2007 Location: Sussex, UK Posts: 317	Quick update, I have found that at any zoom range once focused sharp, there seems to be a bit of free play on the zoom ring. One side of the free play is sharp the other soft, free play travel is about 1.5mm. My other zooms have a bit of freeplay in the zoom ring but it does not change the focus. Now I found this freeplay I can zoom to 200 focus then pull to 70 twist the freeplay and it is sharp. This must be a defect. Paid a quick trip back to 'Park Cameras' and they had no more units in, they sold 4 yesterday. 7-10 days for restock. A young chap had a quick look and agree it was a problem, he only tested it for a couple of seconds and I'm not sure if he was just agreeing with the customer. He told me to use it until they had restock, so I brought it home. Model number UX0918 - September / 2009

October 4th, 2009, 12:09 PM	#3
Don Miller Major Player Join Date: Mar 2006 Location: Chicago Posts: 706	here's a list of parafocal lenses: Parfocality - Canon sez: Canon SLR Lens Talk Forum: Digital Photography Review note this is from 2004

October 4th, 2009, 12:34 PM	#4
James Miller Major Player Join Date: Mar 2007 Location: Sussex, UK Posts: 317	Thanks Don, So it is apparently Parafocal. It's the free play that seems to be an issue, wish I had another to test. Should have gone with the f4 or the Sigma!

October 4th, 2009, 02:06 PM	#6
James Miller Major Player Join Date: Mar 2007 Location: Sussex, UK Posts: 317	Evan, I didn't notice at first because it focuses so well by hand live. It's only when I was trying to get a handle on it's limits on legs I noticed it. I just find I automatically zoom in to focus. If it like this on another copy, I'll just have to treat her like a prime.