Canon 17-40 F/4 L focus lock issues

[MarkNicholas]

I have a 30D and one of my lenses is the 17-40 f/4 L.

I want to start by saying that I love this lens and it works very well on my 30D "most of the time".

However, in low light / low contract conditions I find that the autofocus does not always lock-on. I always use center point focus.

On a recent shoot on NYE using external flash I found that about 50% of shots had not locked on focus. The other 50% were perfect (focus wise anyway).

The viewfinder on the 30D is not good enough for manual focus (particularly at night).

Has anyone out there experience similar problems with this lens and do you have any recommendations on how to get more consistent focus with it is such conditions.

 

[AOKH]

I used the 17-40 on a 20D for years, but always thought it did a remarkable job AF wise (even in challenging conditions). Hope you get to the bottom of your AF difficulties. Regards

I have a 30D and one of my lenses is the 17-40 f/4 L.

I want to start by saying that I love this lens and it works very well on my 30D "most of the time".

However, in low light / low contract conditions I find that the autofocus does not always lock-on. I always use center point focus.

On a recent shoot on NYE using external flash I found that about 50% of shots had not locked on focus. The other 50% were perfect (focus wise anyway).

The viewfinder on the 30D is not good enough for manual focus (particularly at night).

Has anyone out there experience similar problems with this lens and do you have any recommendations on how to get more consistent focus with it is such conditions.

 

[BG454]

I use exactly the same combo and have experienced the identical problem. However, it is not a specific 30D problem. No camera will lock focus on a dark/low contrast subject since there is not enough "information" in the image to allow the AF to operate.

Low contrast and low light are the factors mentioned first and second under "When auto focus fails" on p80 of the 30D operators manual.

On the same page the actions suggested are:

1. Focus on an object at the same distance as the subject and lock the focus before recomposing.
2. Set the focus switch to 'MF' and focus manually.
--

Photographers feel guilty that all they do for a living is press a button. - Andy Warhol

 

[GordonAtWork]

The af performance in low light was deemed to be useless ( the 10D made some progress on that front ) although there was a workaround. Choose an object with a vertical line and use that as a point of reference. Canon could have used the red grid focus assist light from the EOS5 to help but they chose to use a stupid llittle light instead which was in no way bright enough to illuminate anything further than 5 feet.

Using an EX flash as a focus assist tool is good and you can disable the flash from firing using the custom settings so it works like an ST-E2.

--

Given up on the whole "regain my original ID". Seems DPR don't give a flying fucher

 

[Mike K]

to reiterate, to find the appropriate focus point is the responsibility of the body, not the lens. The fact that the 17-40 is an f4 lens just limits the max light available for focusing (at wide open), say Vs an f2.8 lens.

 

[clyded]

I have had auto focus problems with two copies of the 17-40 f4L lens. After about two years the lens would "hunt" and chatter, not being able to lock focus. This happened with high contrast subjects. I sent the lens for repair, and it worked for about a year, then the same problem developed. I then bought a new 17-40 f4L lens, and the same problem occurred after about two years. I have used the first lens with Canon 5D and 5DII, and the second lens with 5DII and 5DIII. I never dropped or misused either of the lenses. In addition to the 17-40, I always carried the 24-105 f4L and the 70-200 f4L in my camera bag. I have not had a focusing problem with either of the other lenses.

 

[jpb4242]

My 17-40 F/4 L auto focus problems are pretty much identical to yours clyded. The lens was repaired once for the same problem, then now about 2 years later the "hunt" and chatter is occurring again. The problems are the same regardless of whether the lens is on a 5DII, 5DIII or 1DsMkIII. All bodies have the same behavior. When the "hunt" and chatter stops (usually after a second or two), it's hit or miss whether the image is in focus or not. The bodies all think the image is in focus and the shutter will trigger but at least half the time the captured image is out of focus.

I was debating whether to repair or replace the lens. From your experience with a new replacement, I'll probably opt to repair it again.

Like you, I keep several bodies and multiple lenses in the same camera bag, which I always handle very carefully. I've not had focusing problems with any other lenses or bodies... just this 17-40 F/4 L.

I have had auto focus problems with two copies of the 17-40 f4L lens. After about two years the lens would "hunt" and chatter, not being able to lock focus. This happened with high contrast subjects. I sent the lens for repair, and it worked for about a year, then the same problem developed. I then bought a new 17-40 f4L lens, and the same problem occurred after about two years. I have used the first lens with Canon 5D and 5DII, and the second lens with 5DII and 5DIII. I never dropped or misused either of the lenses. In addition to the 17-40, I always carried the 24-105 f4L and the 70-200 f4L in my camera bag. I have not had a focusing problem with either of the other lenses.

 

[Johnny Castle]

Resurrecting old thread and hope this will help someone. I got used 17-40 today, in very good condition apart from the AF problem described in this thread.

Guess what, some Russian guy did perfect disassembly and assembly videos, and also nailed the problem being plastic focusing strip and sensor inside the ultrasonic motor assembly.

I followed his videos here and 2-3 hours later the lens focuses like brand new, just amazing. Hope this helps someone with similar problem.