What to do about my messed up 24-105mm F/4 L IS lens?

[Andreos]

I have an older 24-105mm f/4 L IS (manufactured March 2006, according to the date code). I used it extensively on my 5D over the course of several years, and on my last trip with it in the winter of 2010 the IS mechanism started having problems, it would flutter and buzz intermittently and ceased to do any stabilization.

I contacted a local repair shop of good repute and had them replace the IS mechanism. It was a $400 repair once tax was added on. When I got the lens back I did a cursory test and confirmed the IS was fixed and working well. But before I could really give the lens a work out, a family crisis came up, and everything got put on hold for a couple of years....

Fast forward to the present and I am getting back to my photography. I've acquired a 6D to replace my 5D, and having done some shooting, it's clear that my trusty 24-105mm is not up to snuff. This afternoon I did some controlled tests on a tripod, focusing manually with live view so as to eliminate any AF variables. At f/4.0 the lens is very blurry even in the center (all focal lengths). It gets better at f/5.6, further improvement but not as dramatic at f/8.0, and f/11 is uniformly the best. I remember previously on my 5D there was a little bit of softness wide open, but it was not as bad as it is now. I suppose the higher resolution of the 6D is mercilessly revealing something the 5D couldn't resolve, but my other lenses are working very nicely on the 6D.

I am thinking that some critical aspect of the lens optics got messed up at the repair shop. The repair work is far out of warranty, and I don't want to throw any more money at this lens unless it is a sure thing. Recent postings in Roger Cicala's blog have me thinking, there is no such thing as a sure thing, when it comes to lens repair. So I'm debating what to do. I really like the 24-105mm zoom range and have got to have IS. The only direct alternative seems to be the new Sigma 24-105mm, but it's not weather-sealed. I often shoot in dusty conditions so I am skeptical of getting that lens. The Tamron 24-70 f/2.8 VC looks interesting but there's a lot of missing millimeters from 70 to 105! I am actually thinking of buying one of the "white box" 24-105mm lenses that are available for about $700. (And then do what with the old lens? I can't sell it in good conscience.)

I am wondering what some of you folks would do in this situation?

 

[Mt Spokane Photography]

Getting it fixed at Canon is less expensive than a new one, I'd expect around $270. Its not always a bargain at local camera shops, they do not have the tools to properly adjust a lens for accurate autofocus, or some of the other key parameters.

The other alternative is to sell it on ebay, disclose the situation, and get what you can out of it. You can often find a new one that came out of a kit in the $700 range, or jump on one of the deals for the 24-70 MK II.

Don't overlook the possibility that the rear element in the lens is dirty. I bought one one time that the seller said had quality issues, I cleaned a layer of dust off the rear element, and it was great after that. I know its unlikely, but check anyway.

 

[Zv]

Having already thrown $400 at the lens I wouldn't get it repaired if I were you. Buy a white box version and sell the old one on Ebay or CL with full disclosure. If you're lucky you might get a few people who are interested. It works right? Just a bit soft wide open at 24mm or all focal lengths? If only around 24-35mm f4-5.6 this is quite acceptable for this lens. However you mentioned the centre was soft too, is that also the same when stopped down?

Could be a decentered or slightly off element. If that's the case someone will prob buy it from you and get it fixed. That person might even make a profit!

People buy all kinds of junk. It will sell. I would aim at $400, an amount that get's your initial repair fee back. Put that money towards the replacement. Maybe buy a used one for even less than the white box deal? I bought mine used and it's fine, no issues except the 24mm end!

 

[dgatwood]

The first thing I'd do is see if AFMA fixes it. If not, then if I were sitting on a lens that wasn't under warranty, I'd be tempted to try adjusting it myself, under the assumption that the service place probably adjusted it wrong (or not at all) or that one of the screws was loose and the repair person didn't take the appropriate steps to get the lens to stay in adjustment. A quick Google search returned this hit:

http://canonrepair.wordpress.com/2013/01/01/adjusting-the-coaxiality-of-the-3-lens-group-in-an-ef-24-105-is-usm-lens/

It describes how to do a partial disassembly of the lens to adjust the 24-105's alignment.

If you decide to go that route, I'll throw in a helpful tip that I got from a musical instrument repair person: Nail polish is a good way to make tiny screws stay in position.