M5 + EF 100mm f/2 focus issues

Hi everyone! Hoping to get some help here on focus issues I'm having with this combination. I took an opportunity to get an EF 100mm f/2 lens earlier in the summer, and my primary use for it has been for kids' sports, with some occasional portraits mixed in too. For sports, it's been almost all soccer.

The trouble I'm having is that it nearly always, stubbornly focuses on the background and not the player. This is a problem even when the players are moving side to side compared to me, not just when they're heading towards me. I've got to use Servo AF given all the movement in soccer, and on the M5 that means I've got a pretty big AF box to work with - and then that means there's pretty much always some background somewhere in the AF box. My M5 LOVESthe grass in the background, and I'm always getting shots focused there instead of the player that's taking up most of the AF box. I've taken to placing the AF box down low so I'm basically trying to focus at their feet, but the results still aren't great.  I'm usually shooting between f/2.8 - 4, so I've also adjusted to get some more DOF too.

I'd say this is an M5 problem in this situation, but I can typically use my Sigma 56mm f/1.4 in the same situation - except that the player takes up even less of the AF box now - and get MUCH better AF results. So it seems that there may be something I'm missing about the M5 + 100mm f/2 combination...?  If I can't figure something out here, I'm likely going to sell the 100mm and move to something else instead.

Has anyone had similar issues, and could pass along any advice for solutions?

Do you have issues with still images, too? If so, it may be a lens issue.

The USM drive should be quick enough for soccer. Unfortunately I am not familiar with M5 AF. Did you use continous AF drive?

You should be getting some decent results from the M5 with almost all lenses, with one exception.... The Canon EF 100mm f/2 USM lens is a PRE-DIGITAL lens released in 1991.  Canon themselves said that they do not recommend the use of "Pre-Digital lenses" on modern digital cameras, especially on the Mirrorless R-System models, but presumably also on the mirrorless EOS M-System. Quite a few people do use them, and they appear to work.  Many pre-digital lenses work just fine on the M/R system bodies.  But this is an issue that will continue to surface.  In addition, this particular lens was known to have some AF issues in the past, though not the one you described.  In the cases I'm familiar with, this lens would sometimes stop focusing at a certain distance and it sometimes stopped Autofocusing altogether.  There's even some self-repair videos on YouTube on how to get them going again when this happens.
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The reason Canon give for not recommending Pre-Digital lenses on modern digital cameras is because pre-digital lenses (usually anything manufactured prior to 2002) tend to be made with a very different metering in mind, were subjected to the effects of UV light (modern sensors have a UV deflection layer) and use a different method of Auto Focus, especially prior to the DPAF sensors.  Canon also noted that the lens coatings on older lenses are prone to affecting the Auto Focus.  The older USM motors used in the earlier lens designs from the 1980's are on your lens and I assume that they might not be able to keep up.
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In the case of this rarely encountered lens, it's probably going to produce problems similar to the one you've encountered.  You'll notice that your Sigma lens isn't problematic with AF because it's a much more recent lens design with modern optical coatings.

Maxmolly7 wrote:

Do you have issues with still images, too? If so, it may be a lens issue.

The USM drive should be quick enough for soccer. Unfortunately I am not familiar with M5 AF. Did you use continous AF drive?

I don't have the same issues with images of still / non-moving subjects.  Photos are definitely a bit softer at f/2, but I'm usually shooting soccer around f/2.8-3.5 to increase DOF some and cut down on color fringing.

And yes, definitely using continuous AF!  I certainly feel like the AF can keep up, it's just that it would rather focus in things further away in the AF box. That's very strange AF behavior, since in my Canon experience the default AF seems to be "focus on whatever is closest to the camera." 🤔

Marco Nero wrote:

You should be getting some decent results from the M5 with almost all lenses, with one exception.... The Canon EF 100mm f/2 USM lens is a PRE-DIGITAL lens released in 1991. Canon themselves said that they do not recommend the use of "Pre-Digital lenses" on modern digital cameras, especially on the Mirrorless R-System models, but presumably also on the mirrorless EOS M-System. Quite a few people do use them, and they appear to work. Many pre-digital lenses work just fine on the M/R system bodies. But this is an issue that will continue to surface. In addition, this particular lens was known to have some AF issues in the past, though not the one you described. In the cases I'm familiar with, this lens would sometimes stop focusing at a certain distance and it sometimes stopped Autofocusing altogether. There's even some self-repair videos on YouTube on how to get them going again when this happens.
.
The reason Canon give for not recommending Pre-Digital lenses on modern digital cameras is because pre-digital lenses (usually anything manufactured prior to 2002) tend to be made with a very different metering in mind, were subjected to the effects of UV light (modern sensors have a UV deflection layer) and use a different method of Auto Focus, especially prior to the DPAF sensors. Canon also noted that the lens coatings on older lenses are prone to affecting the Auto Focus. The older USM motors used in the earlier lens designs from the 1980's are on your lens and I assume that they might not be able to keep up.
.
In the case of this rarely encountered lens, it's probably going to produce problems similar to the one you've encountered. You'll notice that your Sigma lens isn't problematic with AF because it's a much more recent lens design with modern optical coatings.

Hmmm, interesting. I knew this was an older lens, but never really thought of it in terms of pre and post digital lenses....  It's very clear that my M5 won't go to to it's high speed mode when I use the 100mm, topping out close to maybe 3 FPS.  It does seem like the AF is fast enough, just stubbornly wants to focus further back.

Anyone have experience with the 100mm f/2 on an M6ii?  I'm wondering how much of the issue is paring this lens with the much slower AF on the M5.  I've seen some pretty incredible action shots from 100mm f/2's on R5 and R6's, but those are whole other animals for AF than my little old M5!

The pre-digital info was new for me, thanks for letting us know!