Why doesn’t my camera meter account for a manual hot-shoe flash?

Asked 3/29/2013

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I’m using a Canon EOS 1100D / Rebel T3 with a Neewer TT560 flash on the hot shoe. With the built-in flash, the camera seems to expose automatically, but with the external flash the meter does not change and my images are overexposed.

Is this normal behavior with a manual flash, or is it a limitation of the camera? Can the camera meter be made to recognize the flash, and if not, what’s the best way to expose correctly when using this type of flash?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

13y ago

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It's not a fault of the camera, it's the nature of the flash.

While we tend to think of a camera's hot shoe as an attachment point for a flash, it's actually an accessory shoe that can accept a flash. (Other typical uses include accessory optical or wire-frame viewfinders, GPS units, video lights and shotgun microphones.) The centre, large connector terminal in a hot shoe and the outer shoe are short-circuited when the first curtain of the shutter is completely open; that's what make the shoe "hot". That circuit is dumb; the contacts are shorted when the front shutter is open regardless of whether the camera is properly set for a flash exposure, or whether or not a flash is present at all.

Manual flashes (or flashes that have their own "auto" mode) are triggered when the centre terminal and the sides of the shoe short out. They normally only have contacts at the top of the foot (the part that fits into the shoe) and at the centre terminal. They have no way of telling the camera, "hey, I'm a flash." They also have no way of knowing what the camera is doing, so your flash will happily trigger when you have the shutter set to 1/4000 even though it will do absolutely no good (only the tiniest sliver of the sensor will be exposed when the flash fires, and that tiny sliver won't be open for as long as the flash is firing if you're working at any sort of distance at all).

Flashes that use through-the-lens (TTL) metering need to be able to communicate with the camera using a more sophisticated language than a "fire right now" signal taken directly from the shutter. That's what the extra contacts on your hot shoe are for. Not only does the camera know that there's a flash attached, it can also tell it how to adjust its power output (for both the TTL metering pre-flash and the "real" exposure flash), but it can also tell it to fire at a time different from when the front curtain opens. (For instance, with high-speed sync, it tells the flash to begin pulsing when the front curtain begins to open, and in rear-curtain sync it tells the flash to fire just before the second curtain begins to close.)

Originally by user2719. Source · Licensed CC BY-SA 4.0

user2719

13y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

Yes—this is normal. Your Neewer TT560 is a manual flash, so the camera cannot meter it the way it can the built-in flash.

A camera’s meter only sees the ambient light before the exposure. With TTL-compatible flashes, the camera and flash communicate through extra hot-shoe contacts and use a preflash so the camera can calculate flash power. A manual flash usually uses only the center firing pin, so the camera can trigger it but cannot control or meter its output.

So the meter won’t “know” about the flash in advance.

To expose properly with a manual flash, you typically:

  • set camera exposure for the ambient light
  • set flash power manually
  • adjust aperture, ISO, flash power, and flash-to-subject distance as needed
  • take a test shot and refine from there

If the flash has its own auto mode, you may be able to use that, but it still won’t behave like Canon TTL.

If you want the camera to automatically account for the flash, you need a Canon-compatible TTL flash rather than a fully manual unit like the TT560.

UniqueBot

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13y ago

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