Problem w/ AF-Assist Lamp Using CLS Flash

Discussion in 'Nikon' started by chip_chipowski, Jul 16, 2014.

  1. I recently experienced a problem with the AF-assist lamp on my D300. My set-up was: D300 w/ Sigma 30mm, SB-800 connected via hot shoe cord (SC-28 3rd-party equivalent) set as CLS master, SB-700 set to remote.
    As the available light disappeared, I realized the AF-assist lamp was not kicking on. I checked the menu on the camera and each flash, to make sure AF-assist was not turned off. In fact, all devices showed the AF-assist light was on.
    I have looked through the manuals, but I find no clue as to what the issue could have been. I am not experienced using CLS or off-camera flash, so I am wondering if it is some kind of quirk in my set up. Is CLS a red herring? I don't think the Sigma lens should be a factor, I've never had a problem with this lens and the AF-assist lamp. Any insight would be greatly appreciated.
     
  2. Which AF setting were you using on the camera? On some cameras this determines whether the AF assist lamp turns on.
     
  3. I have AF assist light turned off normally so I don't have a lot of experience with this, but I suspect the issue could be that when you have a CLS flash connected via TTL cord on the hot shoe, the camera may assume the flash or the cord (SC-29) will emit the assist light, and the on-camera assist light is not needed. Just a guess. The SC-28 doesn't have the light on the part that goes on the hot shoe but the SC-29 does. Does the SB-800 show the assist light active?
    Another possibility is that to get AF assist light to function, single shot autofocus mode (AF-S) must be on; I recall it doesn't function in AF-C mode.
     
  4. single shot autofocus mode (AF-S) must be on; I recall it doesn't function in AF-C mode.​
    Yup, good guess. I'd like to see AF assist ON (in AF-C) as a selectable menu option.
    The AF assist on flash, or SC-29, follows the same rules as the on-body AF-assist lamp. In AF-C, it's all dark!
     
  5. Yup, good guess. I'd like to see AF assist ON (in AF-C) as a selectable menu option.​
    Silly question... do all Nikon flashes use separate lights for AF-assist? If AF-C is active, that would mean the assist light would be on for as long as the user was requesting focus. If any Nikon flashes use the strobe for AF assist (like my Canon Eos 300D does), I imagine that might lead to some heat/power issues. That may be a red herring; just a thought.
     
  6. assist light would be on for as long as the user was requesting focus​
    If there was some easy way to get at the half-press/full press signal for an aux focus assist LED light with it's own 2 x AA power source...I'd buy one for £15.
    How long does 'request focus' work for after you lift your finger off the shutter button?
    AF Assist light 'ON' on first or half-press...and 'OFF' on finger-up.....and 'OFF' on full press.....I can't see a issue, unless I'm missing something...which is quite possible!
     
  7. If you connect an iTTL flash, the assist light on the camera is disabled and the light on the iTTL flash works instead, no?
     
  8. the assist light on the camera is disabled and the light on the iTTL flash works instead, no?​
    Yes it does, but as far as i know it only illuminates in AF-S focus mode.
     
  9. Thanks everybody - I think you guys nailed it with the AF mode. I'm not 100% certain I was in AF-C at the time. But I just did a quick check on my camera and toggling b/w AF-S and AF-C determines whether the AF-assist comes on (ie AF-S = lamp, AF-C = no lamp).
    I appreciate the help!
     
  10. ShunCheung

    ShunCheung Administrator

    Right, you need to use AF-S (single) instead of AF-C (continuous). Additionally, only some AF points would trigger the AF-assist light. The center AF point definitely works. The other AF points in the center column (with the camera in the horizontal orientation) should also trigger the AF-assist light. Once you start using the outer AF points, the AF-assist light doesn't turn on any more.
    That behavior varies a bit with different camera bodies so that I don't remember the exact pattern for each camera, but always check starting from the center AF point.
     
  11. When in doubt, Nikon ViewNX 2 will show the specific focus mode, and most other metadata that won't show in any other photo viewer/editor. Helps to narrow down reasons for specific camera behaviors, including focus errors by showing the specific AF sensor used in some modes.
    As Shun described, some Nikons may use the AF assist lamp only with the AF sensor in the center position. For example, the V1 AF assist lamp works in AF-A or AF-S, but not AF-C (continuous), and with the single AF sensor only in the center position. Moving the single AF sensor off center seems to disable the AF assist lamp. It works in area/multi AF mode, but not in subject tracking mode.
    I'd need to dig my D2H, SB-800 and SC-29 cord (which features an AF assist lamp) out of the closet, but overall it behaves as described. However I can't remember whether the AF assist lamp works when AF is assigned to one of the 11 single AF sensors off-center.
    In actual practice the D2H and V1 are so sensitive in dim lighting the AF assist lamps seldom come on anyway. I see the AF assist lamp much more often with the Fuji X-A1, which isn't quite as sensitive for accurate AF in dim lighting.
     

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