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Tamron 24-70 mm F2.8 - Slow to Focus (?)

Hi - I worked an event last night, a VIP reception for a film maker. It was a smallish room with about 120 people. I didn't need the length since it was tight quarters, so I went with my Tamron 24-70 mm lens on my Canon 6D. I haven't used it in a bit. It was pretty slow to obtain focus from time to time. Anyone have this lens and this issue? Also, could it be that the focus assist from my on-camera flash (Canon 580 series) is turned off? I haven't looked at that yet, but if anyone can tell me easily how to check that, I would appreciate it. I have a feeling that's switched "on", because my other lenses are not having a problem. Or, maybe those other lenses just don't need it (?).

Thanks - Dave


  • CanonJayCanonJay Member
    edited September 2017

    Check your menu under C.Fn II -5 on the camera body.  If should be set to ( 0 ) Enable. Also if I remember correctly, the speed light must be set to emit beam. The speed light will override the camera menu. On your 580 flash check C.Fn-08 and set to 0 also. 

  • Neil vNNeil vN Administrator
    Next step ... check that your AF assist actually works. 
    Also make sure  you weren't in servo mode - that disables the flash's AF assist beam.
  • Neil and Jay - Thanks, I'll check these things out. Also, I never use Servo Mode, so I know that wasn't the problem.

  • Also, I've had no trouble with my other go-to lens (24-105 F4 Canon), but I will still check out the beam to see if it works.

  • Well, I don't know. It must have been a fluke, or something I was doing wrong, not sure. I just looked at the two custom-function settings, and they were set correctly. Tested the thing out, and I could see the AF assist beam coming out. It's supposed to look like a few red vertical stripes, right? (when the flash is vertically oriented). Shut the lights of in the kitchen, and focused on small kitchen cabinet knobs. Snapped right into focus.

    What's bothering me is the responses I got from people on the Tangents and SLR Facebook pages - "crappy lens", "never focused right", etc. stuff like that.

    I think it was me doing something a bit off.

  • Yup. red lines is correct. Most likely a fluke or environmental anomaly.  I wouldn't sweat the lens. I am sure the lens is more than acceptable for what you're using it for.  It sometimes amazes me that people bash gear so much sometimes. I am pretty confident, I can get an acceptable photos on just about any camera and lens combo out there. Sure there is better gear for each job and may not be the best use for it, but hey, in the right hands and some practice and knowing the limitations of the gear it will work just fine. (Not talking about your lens Dave. Just gear in general). 

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