I'm seriously considering getting the 18-135 STM for outdoor work with the C100 where I know people / vehicles etc will be moving around constantly so AF would be useful.

Is the AF in such circumstance relatively reliable / fast etc or am I going to be disappointed?

I've seen lots of tests where people are moving the camera to static objects around a room, but none that are tracking moving vehicles, athletes etc.

Also, if I happen to zoom a little (slowly) during shooting (not something I do very often) does the AF maintain focus well enough since this doesn't appear to be a par focal lens.

How does the C100 deal with the variable aperture?

How happy are you with this lens wide open at wider angles, say 18-40mm ?

Dave I have the 18-135 STM lens, but I use it on a 70D. There is a thread where they are talking about using it with a C100 and the lens. I have never try zoom when shooting video yet.

http://www.dvinfo.net/forum/canon-cinema-eos-camera-systems/521547-best-general-usage-lens-c100.html

Thanks Michael, I've read that thread (lots of people recommending the 24-105 which I already have) but it doesn't really address my questions on AF tracking of moving objects, especially those coming towards you or away from you.

Canon Objektiv STM 18-135mm an der Canon C100 (Video Samples) - YouTube

Thanks for that. My german (I assume it was german) is not that good so I didn't really get the audio part, but there was still a little more jumpiness than I'd hoped. Maybe this will be fixed by the new upgrade coming.

Hmmmm... I guess I should wait for that and see how my 24-105 works first.

I use that lens as my run and gun for the church. I like continuous AF. It is silent

Just got one. going to have a play with it over the weekend. First test not brilliant. A little too slow for my liking I think. But the DSLR Newshooter test of the new dual pixel auto focus looked a little too fast! Maybe I need something in between…

I have a 18-135 STM lens but it will not do continuous auto focus although the one shot auto focus works fine. I have the latest firmware installed. Any ideas about what the problem may be?

This Canon C100 autofocus upgrade film tutorial has been posted up on Vimeo.

Handcrafting Unique Wedding Films with the EOS C100 Digital Video Camera on Vimeo

Sorry to be a little late to the party.

I have this lens on the C100. I was initially excited by it in the camera store, but once purchased, I was hit by a huge dose of Buyer's Remorse and ended up hating it quite a bit due to its fly by wire characteristics:

Canon 18-135 STM tests on C100 on Vimeo

This compares the 18-135 STM with the 'Classic' 24-105 L

BUT there are two things I've learned since then, which change the whole dynamic of the lens:

1) Switch on Zoom Iris Correct (Camera Setup --> Iris --> Zoom-Iris Correct)
2) Switch on Peripheral Lens Illumination (Periph. Illum. Corr. in the Camera Setup menu)

I found the Continual AF a bit underwhelming, but looking forward to the new Dual Pixel quasi-phase-detection update, which should really transform this lens.

Thanks for the info Matt. It's very informative. The problem that I'm having with the 18-135 lens is that it will not operate in AF mode. One shot works fine but not AF. I have the latest firmware that should support AF on the 18-135.

I found the Continuous AF mode, erm, 'ponderous' - taking a few (!) seconds to kick in. Even then, it might need a recomposition to initiate it. No, not good. I could see how it would appear to be not working. LOL

Thanks for the replies guys. I'm going to skip this one for now I think and just use the XF for the moving shots until the C100 gets the new AF upgrade and we see how it's performing.