RF 100-400mm f/5.6-8 IS USM - Focus ring not responding

[Fabri91]

I recently purchased a RF 100-400 mm lens, to be used with my EOS R8.

The lens seems to be working fine, but it's the first one that I have that has a separate focus ring and control ring, and I suspect that there may be an issue with the focus ring.

Specifically:

• Autofocus seems to work fin
• When selecting MF on the lens the camera correctly detects this change in setting
• When in MF mode the focus ring does not seem to do anything

Am I missing anything to be able to manually focus? Using the kit lens (24 - 50 mm) this seems to work fine - since that lens only has a single ring, I also have to select the function "Focus" instead of "Control" on the lens itself, as expected, in addition to selecting "MF". The lens then reacts to the ring commands.

Is there any way (a diagnostic function, perhaps) in which I could specifically verify that the focus ring encoder is working?

Thanks!

[FloridaDrafter]

I may have an old manual, but per page 439 of the R8 advanced user guide, go to the AF6 menu and make sure that "Electronic full-time MF" is enabled. Also, and it should be in that same AF menu drop down, set up "Lens electronic MF". On my R6 II, I have the latter set to "One-shot-->enabled" and my wife sets it to "One-shot-->enabled (magnify)" so she can fine tune focus.

Check out those settings and see if MF works with the RF 100-400. BTW, I do have this lens and manual focus override works perfectly on my R's.

Newton

[FloridaDrafter]

I would just like to add, since I don't have the R8, manual focus override (MFO) works differently from camera to camera and lens to lens, at least that's the way it's been on my DSLR's, for instance you may have to do a half press of the shutter button to get MFO to kick in. There are also a couple of features you may be interested in, seeing as you are interested in manual focus. One is "Manual focus peaking" and the other is "Focus guide" (page 441 in the manual).

Newton

[Fabri91]

I already had "Electronic full-time MF" set to ON and the subsequent option, "Lens electronic MF" set to "One-shot --> Enabled".

This seems to work fine with the kit 24-50 lens, but again no response using the focus ring on the 100-400.

The highlight and focus options were also already enabled - I successfully used the camera in the past with some older DSLR lenses where manual focus was the only option. Especially in those cases these functions were super helpful.

In this case, however, I am less interested in the manual override of the auto-focus, and more in the full-manual mode, especially to determine if there is a focus ring issue or not - there too the focus ring seems to not be responding on the lens specified in the title.

[FloridaDrafter]

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@Fabri91 wrote:

In this case, however, I am less interested in the manual override of the auto-focus, and more in the full-manual mode, especially to determine if there is a focus ring issue or not - there too the focus ring seems to not be responding on the lens specified in the title.

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If the AF/MF switch on the lens is set to MF and it won't manually focus, then the lens switch or ring are defective. When you set the lens to MF do you see "MF" in the EVF? If so that would indeed point to the ring.

There are no settings in the camera, that I am aware of, that will override the on lens switch when set to MF. Only the AF setting can be overridden.

Newton

[Fabri91]

The camera responds correctly to moving the MF/AF switch, indicating the expected mode on the display/IVF.

[FloridaDrafter]

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@Fabri91 wrote:

The camera responds correctly to moving the MF/AF switch, indicating the expected mode on the display/IVF.

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That's a shame. There is one other possibility, but you seem to be on top of it so it's a long shot. The focus ring "sensitivity" might be so high that you just don't notice MF working. I know it sounds crazy, but I've done this myself. To clarify, the sensitivity might be so high that only rotating the ring a small amount actually advances focus more than expected and sharp focus is bypassed depending on how fast you move the ring, MFD to infinity with just a small movement of r\the ring. One sure fire way to tell if the ring is working is to enable "Focus guide" (AF4). If you don't see the guide in the EVF, I would probably return the lens, but I have very little patience, LOL!

Newton

[Fabri91]

Alas I already tried it - no change, again confirming with the other lens how things should work.

I also tried to rotate the focus ring through some complete rotations in both directions, just in case this made the encoder "engage" somehow as a long shot, but alas no change in this case as well.

I'll most likely return the lens to the reseller - it's good that I noticed the issue quickly, anyway.

Thank you for your help in walking me through testing!

[FloridaDrafter]

It's a nice lens so I hope you get another quickly  🙂

Newton

[Fabri91]

Just to ensure that I've described the issue correctly, I also just made a short video showing the issue and the expected behaviour (shown with the 24 - 50 mm lens): https://www.youtube.com/watch?v=V3Vt6uMlB4g

Pardon the terrible quality, but the steps taken should be visible.