Help needed with 40D, 580EXII and AF assist beam

NeilLNeilL Registered Users Posts: 4,201 Major grins
edited August 31, 2010 in Cameras
Tonight a friend was kindly posing for me in the small room in my house I use as a studio. I had my 40D on a tripod with a remote release and with mirror lockup enabled, and the 580EXII on a stand with an umbrella near my friend. The 40D and flash were connected with a E-TTL hotshoe cord. I set the flash to manual auto and did some test shots of my friend in dimmed-down room light to position the gear and get into the ballpark for correct exposure. Everything worked perfectly. My plan was to use flash modified by the umbrella, and a reflector as the only light sources. The background behind my friend was black calico. So having got everything ready and positioned the central focus point where I wanted it on my subject, I switched off the room lights. We were in total darkness. I depressed the button of the remote release halfway, but did not see the red pattern of the AF assist beam fire, and the camera hunted for focus unsuccessfully.

I then went through and checked and rechecked all the relevant C.Fn and other settings on the camera and flash. Tried again, with the same result - no AF assist beam, and no focus.

This wasn't what I expected, and I don't know why it was happening. I'd appreciate it if someone could help out.

Neil
"Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

http://www.behance.net/brosepix

Comments

  • ziggy53ziggy53 Super Moderators Posts: 24,130 moderator
    edited August 31, 2010
    See if the flash works properly when attached to the camera's hot-shoe. If it does work correctly, replace the off-camera cord or at least clean all of the contacts.

    If you have 2 - 580EX flashes use one as master and the other as slave. The master should emit the AF assist light. You can always trim the master flash output way down so that it has little impact on the exposure.

    Likewise an ST-E2 transmitter will work and it will provide the AF assist light.
    ziggy53
    Moderator of the Cameras and Accessories forums
  • Dan7312Dan7312 Registered Users Posts: 1,330 Major grins
    edited August 31, 2010
    I just did a couple of tests using a 7D and 580EX (not II) and mirror lockup. With the 580EX on camera or on a Canon flash cable, the focus assist beam lights on the first button push (that locks up the mirror) and the flash fires on the second button push.

    I also tried it with an ST-E2 and it behaves the same way, the focus assist lights up on the first button push and the remote slave flash goes off on the second button push.

    So unless the 58EX II does something really different you should see the red lines on the wall on the first button push.
    Dan

    http://www.danalphotos.com

    http://www.pluralsight.com

    http://twitter.com/d114
  • ziggy53ziggy53 Super Moderators Posts: 24,130 moderator
    edited August 31, 2010
    I suspect it is the Manual but "Auto" mode, which the 580EX does not have, which may causing the AF assist not to light. We will know if/when Neil tries the flash directly attached to the hot shoe.
    ziggy53
    Moderator of the Cameras and Accessories forums
  • rwellsrwells Registered Users Posts: 6,084 Major grins
    edited August 31, 2010
    The red focus pattern will not shoot through, or bounce from an umbrella correctly. Nope, ain't gonna' happen deal.gif
    Randy
  • ziggy53ziggy53 Super Moderators Posts: 24,130 moderator
    edited August 31, 2010
    I just noticed the use of mirror lock up (MLU). I don't believe that AF is possible with MLU, so the AF Assist light would not come on.

    Neil, why are you using MLU?
    ziggy53
    Moderator of the Cameras and Accessories forums
  • Dan7312Dan7312 Registered Users Posts: 1,330 Major grins
    edited August 31, 2010
    AF Assist does work with mirror lockup, the red lines come on on first button press. Second button press fires shutter. I knew I had used it in the past, but I just retried it to confirm it for the 7D before that last email. I used it on my 10D too, but I no longer have that body to try the test again to confirm it.


    ziggy53 wrote: »
    I just noticed the use of mirror lock up (MLU). I don't believe that AF is possible with MLU, so the AF Assist light would not come on.

    Neil, why are you using MLU?
    Dan

    http://www.danalphotos.com

    http://www.pluralsight.com

    http://twitter.com/d114
  • NeilLNeilL Registered Users Posts: 4,201 Major grins
    edited August 31, 2010
    Ziggy, Dan, Randy... thanks so much for jumping in so promptly to help!thumb.gifthumbthumb.gif

    Ziggy, I did the testing that you suggested, and the AF assist light etc all worked as expected. I was using mlu as a precaution against camera shake, I had the 135mm on for very close head shots.

    Dan, really appreciate your doing that investigating. As I just said to Ziggy, yes the AF assist does operate with this setup, and exactly as you describe, first shutter press is focus.

    Randy, I think you might have hit the bullseye! I think I had the flash reversed on the stand, with the beam pointing into the umbrella. When you mount the flash onboard the camera you have no choice, the beam must face forward. I notice by looking at the reflection of the beam on the wall that it is a narrow vertical pattern. As you point out, this would be scattered off the umbrella if pointed into it, and so not function to help the AF as intended. I'm hoping this is the solution, and I'm looking forward to trying again tonight with the same setup when I can get total darkness in the room - the 135 f2 and 40D can lock focus with even the faintest peep of illumination... and apparently without the AF assist beam. Nice to have that problem, eh?mwink.gifD

    Once again, many thanks, guys. Great help!

    Neil
    "Snow. Ice. Slow!" "Half-winter. Half-moon. Half-asleep!"

    http://www.behance.net/brosepix
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