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Canon off-camera TTL Flash - why doesn't it work

LoriclappLoriclapp Member
edited September 2013 in flash & lighting
I have been watching all the video tutorials I can find, I have gone to classes, and I have read everything I can find on using off camera flash. My question is this.....Everyone makes it sound like, if you put your flash on ETTL, your flash will fire perfectly to light your subject as little or as much as needed. So why, when I use ETTL, does it sometimes blow out the subject, or not even seem to reach the subject even though it's very close, etc.? ETTL just does not seem as reliable as everyone else acts like it is!!

If you need more info, I shoot Canon 5d MKII, PW Mini TT1 and Flex TT5, Canon 580EXII
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Comments

  • Are you adjusting FEC to compensate for darker/lighter tones in the image? For example, when I photograph someone against a light background, I usually dial in at least +1 FEC. If I don't do this, then the image is under-exposed because the camera's meter sees the light tones as neutral tones. I do the opposite when the subject/background is dark. Hope this helps.

    Justin
  • hey Lori,

    sounds like something is not right. E-TTL is pretty consistent...I too am a Canon shooter and use the 580EX II and have no issues. You do need to ride the FEC depending on the reflectiveness of the subject. Do check your FEC settings and reset all the CN's to default.

    Rudy
  • Lori

    I suspect it may be the PW Flex and Mini.
    I've got a pair, and don't use them anymore, due to lack of consistency.
    I contacted PW direct and they suggested the following and in order -
    .
    1. Turn on flash
    2. Turn on Flex
    3. Turn on Mini
    4. Turn on camera
    5. Take a sync shot at 1/125th of second.

    Make sure you have latest firmware, and then reset units back to factory defaults. To reset, hold TEST as you power on for 10 secs until you see 4 green blinks.
    .
    I've even tries the soft shield and the same crap occurs.

    BTW I shoot with Canon 1DX and 1DSMK3 and have same problems with consistency.

    Let me know. How this goes.
  • Thanks for the advice - I will keep working on it and let you know how it goes! I appreciate the help
  • ETTL uses the same metering system your camera's ambient light meter uses. The cameras light meter has nothing to with with flash, it can only meter ambient light. ETTL gets it's exposure information from the pre flash.

    Like your we all know when no flash is used if you take a picture (with no compensation) of black tar the image will be overexposed. Snow it will be underexposed. If the is an even amount of tar and snow the image will expose properly.

    The factory setting for your flash Evaluative. Again this no the ambient metering mode. Is is via the flash menus in the camera. Evaluative has multiple metering zones. The flash compares the ambient reading to the pre flash and isolates the closest object which is usually your subject. It then takes a reading off that object/subject. A bride in a white dress, a groom in a black tux and the bride and groom will all reflect light back differently. Here we adjust FEC as require to compensate.

    There is an Average option as well. When in this mode the flash meters the entire scene. So if a bride is in the fame there is typically some area of dark around her lets say for example at the reception. It balances out the scene a bit more. Some photogs prefer Average for this type of environment and use Evaluative for outdoor flash.

    Throw in off camera or bouncing and that changes the pre flash calculations even more. Most new lenses provide distance information. Canon told me that distance information is just a confirmation and the pre flash is the primary data the system will use for the flash exposure. As soon as you raise the flash head or swivel it is disabled.
  • Neil vNNeil vN Administrator
    Loriclapp said: Canon 5d MKII, PW Mini TT1 and Flex TT5
    Here is your problem - the PocketWizard TT5 units and the 580EX II.

    The 580EX II flashes emit Radio-Frequency noise that interferes with the PocketWizards.

    There are a few cures for this:
    http://neilvn.com/tangents/canon-wireless-ttl-flash-options/
  • Guess I was on the wrong track with this one. I have never owned PW. Sorry about that.
  • Thank you!! And Zenon - that was some great information you shared - thank you for that!
  • Glad that helped a bit. Video 3 - ETTL 2 metering is a pretty good video.

    http://cpn.canon-europe.com/content/education/masterclass/canon_flash.do
  • Zenon - thank you SO MUCH for the above link! I am always looking for that kind of stuff to help me understand flash - and this one is awesome!! Thank you!!!!
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