Canon EF 24-105 IS L manual focusing - is it a problem?

Question

I never really used manual focusing before, so I only noticed it now:

• when I switch to MF and slowly turn the focusing ring, nothing happens at all. The ring turns and turns but nothing else happens.
• when I move the ring a little faster (kind of "normal speed"), everything is okay, I can actually adjust the focus.

It's kind of hard to describe but I hope you understand what I mean. It's almost the same behavior as described in this post, but with the slight difference that I can achieve manual focusing apart from when moving the ring slowly.

This is my first L lens as well, so I can't test it with any others. If you have either the 24-105 or any other comparable lens, do you also experience that behavior and do you think it's normal?

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EDIT: as everybody knows, a picture is worth more than a thousand words, so please see also see a video of the behavior.

Answer 1

Canon lenses with an Ultrasonic Motor have natural slippage between the focus ring and the lens' focusing elements.

The technology for this type of AF motor was first developed by Canon, who refers to it as an UltraSonic Motor (USM). It has since been adopted by many lensmakers and is known by such monikers as Silent Wave Motor (SWM) - Nikon, Supersonic Wave Drive (SWD) - Olympus, Supersonic Drive Motor (SDM) - Pentax, Supersonic Motor (SSM) - Pentax, Hyper-Sonic Motor (HSM) - Sigma, and Ultrasonic Silent Drive (USD) - Tamron.

When you reach the end of the focus travel in either direction you can continue to turn the ring forever and it will just slip. If you turn the focus ring in the opposite direction it should move the lens no matter how slowly you turn it.

If the lens is at the minimum focus distance and you turn the focusing ring clockwise as viewed from behind the camera, the ring should slip. If you turn the ring counterclockwise any movement of the ring should move the lens until you reach the other end of the lens' focus travel just past infinity.

If you are turning the focusing ring very slowly in a direction that should move the lens and the lens is not moving, but a faster, more forceful movement does move the lens, your lens needs to be examined by an authorized Canon Service Center or other lens tech that knows what they are doing. It could be that the "slippage" just need to be adjusted. It could also be that the focusing helicoids and/or collars have been warped or mis-shapenned and need to be replaced. When this happens, though, it is usually only at one focus distance somewhere between MFD and infinity.

I've not heard of this being much of an issue with the EF 24-105mm f/4 L IS. The EF 50mm f/1.4, on the other hand, is very easily damaged if bumped from the side while the focus is near the MFD and the front of the lens is extended. When the problem first begins to occur, a quick, forceful movement of the focusing ring will usually move the lens. If the issue is a bent collar or helicoid, or worn out rollers on the guides that follow the grooves, the problem will usually get worse until eventually the lens will be stuck and neither manually moving the focusing ring nor trying to use AF will move it past the rough spot.

Based on the video that has been posted since the above was written, I'd be inclined to believe that the end of one of the slots in the focus helicoid has become misshapen on the short focus end. It's also possible a screw holding the nylon roller that moves up and down the slot has become loose.

Answer 2

when I switch to MF and slowly turn the focusing ring, nothing happens at all. The ring turns and turns but nothing else happens

It can be difficult to notice very small focus adjustments, particularly when they happen slowly. That's especially true when you've focused on a distant object with the lens zoomed out to the wide end (24mm) of the lens's range.

Try setting the focal length to 105mm and point the camera at something just a few feet away from you. Adjust the focus so that the subject is in focus, and then turn the focus ring slowly in either direction: I bet you'll see the subject go out of focus very quickly, even when turning the ring only a tiny bit.

Also, know that the EF 24-105mm f/4L has full-time manual focus — you don't have to set it to the MF setting to get the focus ring to do its thing. This is especially handy if you've set up your camera for back button focus or if you use the "one shot" AF mode, since you can have the AF system focus on the subject, but still easily make any small focus adjustments you might want.

This is my first L lens as well, so I can't test it with any others

The "L" designation really doesn't make a difference here. "L" indicates a higher build quality (weather sealing, more durable materials, etc) and often better image quality.

If you have either the 24-105 or any other comparable lens, do you also experience that behavior and do you think it's normal?

It's hard to know exactly what you're seeing, but I can certainly create a situation where it's difficult to see a change in focus. Again, it's most pronounced at short focal lengths and when focusing on distant objects. You'll still see the change eventually, but because you're turning the focus ring slowly, you need to turn it for a longer time period just to get to the point that you reach quickly when you turn the ring faster. As well, it's easier to see the change if it happens quickly.

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Update: From the video you posted, it's clear that your lens isn't functioning properly. Turning the focus ring counterclockwise (viewed from the back of the camera) with the lens focused at the left end of the macro region should cause the focus indicator to change immediately, no matter how slowly you turn the ring. I'd send that lens in to Canon for adjustment.