Why no TTL

Discussion in 'This or That? (MFT only)' started by Aegon, Dec 3, 2011.

  1. Aegon

    Aegon Mu-43 Veteran

    334
    Nov 3, 2011
    Portland, OR
    Is there a technical reason why mirrorless cameras don't do old-style TTL flash with just a quench pin?

    DSLRs have a separate light path for mirroring, so ostensibly a good reason exists to preflash. But ยต43 meters off the sensor. Seems like they could support TTL pretty easily.
     
  2. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    The Olympus OM cameras that had auto exposure used OTF (off the film) TTL. This method used a photo cell in the mirror box to read the reflected light off the film, when enough light was received for correct exposure the flash was quenched. I believe there is not enough room for a photo cell in what would be mirror box in the m43's.
     
  3. nickthetasmaniac

    nickthetasmaniac Mu-43 All-Pro

    Jan 11, 2011
    But isn't the sensor itself the meter in MFT?
     
  4. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    Not sure it is the meter. It could be that since a pre-flash is required for wireless TTL, the camera sensor (meter) will in effect over ridden by the flash and camera cpu. I suppose wireless TTL is future.
     
  5. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    Technically, everything on a mirrorless cam is TTL (through the lens)
     
  6. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    Maybe just because they wanted compatibility between the new cameras and old flashes.
     
  7. cameronp

    cameronp Mu-43 Rookie

    20
    Oct 10, 2011
    Kent, UK
    I suspect it isn't possible to read data off the sensor fast enough to do this, so you'd need a separate light meter somewhere between the lens and the sensor, which would kind of defeat the point.
     
  8. Aegon

    Aegon Mu-43 Veteran

    334
    Nov 3, 2011
    Portland, OR
    I've been thinking about it too, and I agree with you cameronp, that it probably can't read the data from the sensor fast enough. Metering can happen at 60/120 Hz or thereabouts. Flash pulses are much faster.