bounce and TTL

Discussion in 'Lighting Forum' started by rolling green, Mar 4, 2013.

  1. rolling green

    rolling green Mu-43 Regular

    Dec 31, 2012
    city of chi
    New to flash photography and I must say it has changed my photos tremendously (EM-5 and FL600r). Still trying to figure out what is under and over-exposing shots and have 2 quick questions.

    1) Most of my flash shots are used with TTL and bounced off the ceiling or wall from behind. If I'm using TTL and bounce the flash is it a rule of thumb to increase the flash EV due to the distance and power diffused from the bounce? Or does the camera know from a how much light is coming back thru the lens and make adjustments? If bouncing, is it better to use manual mode and adjust the power of the flash for each photo being taken?

    2) when using the FL600 remotely I need the OM-D flip up flash to trigger the FL600. Does this defeat the purpose of remote flash because the flip-up flash is still coming head on? Or does the flip up flash fire at a minimum level to not affect the shot? Would hate to use the FL600 from an angle to create desired shadows only to see the flip up flash fill all the shadows up.

  2. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Real Name:
    1. It shouldn't need to because it's TTL but sometimes it still does as the flash calculations are made with a pre flash, so yes you will occasionally need to add some power.

    2. It won't show because the trigger will fire before the main flash does, not during the actual exposure. Unless of course you have the little flash turned on as part of the exposures in the RC menu.

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  3. inkista

    inkista Mu-43 Veteran

    Jan 13, 2012
    San Diego, CA
    TTL basically works by the camera telling the flash to throw out a "preflash" burst of light of a known brightness, metering it, and then adjusting the flash power accordingly. So, yes, the camera knows how much light is coming back through the lens and makes adjustment, and no, it's not a rule of thumb that you will need to add compensation every time.

    However. Because TTL is metering-based, it can be thrown off by all the usual things that throw metering off. White targets, black targets, distance, and the limitations of flash output.

    Just as when you shoot in an automated mode like aperture or shutter priority and you ride exposure compensation to get where you need to be with metering-based settings--you need to ride the FEC with TTL automating your flash power.

    Depends. If you have the time, and you're shooting in consistent lighting and not moving around or changing the scene in the camera (say, a studio-type situation), then Manual will give you more control and consistency. But in a run'n'gun event situation, such as chasing someone around a room in and out of varying lighting conditions and scenes, then TTL is probably a more convenient tool to use.

    Think of it like switching between M mode and aperture priority on the camera. It depends. Bouncing doesn't really affect matters too much one way or the other, except that manually doing distance calculations in your head while bouncing (you have to think of the distance the light travels to the bounce surface and from the bounce surface to the subject, not just how far you are from the subject) can be a bit harder, and TTL can eliminate having to do that.
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  4. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    Real Name:
    John Griggs
    When you are in RC mode, you can choose the mode for the on-camera flash and one of those options is "off". In that case it will only fire to trigger the other flash and not during the exposure as mentioned previously here.

    Sometimes when I bounce wireless though, I do use some of the little flash for "catch lights" in the eyes of folks.

    It is possible to link your exposure compensation to the flash compensation. This gives you easier shot by shot control using a control wheel usually. This has worked for me more simply than trying to control either exposure compensation or flash compensation alone.

    I had good luck with the FL-600R and FL-36R flashes in TTL mounted on the camera, except for once when I had the mode in simple "Auto" rather than "Auto TTL". In auto mode it uses a sensor to fire a controlled amount of light metered by a sensor on the flash -- I'm sad at the amount of time it took me to figure that out, lol.
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  5. fin azvandi

    fin azvandi Mu-43 All-Pro

    Mar 12, 2011
    South Bend, IN
    Unless Olympus changed something in the RC flash system between the E-P3 and the OM-D, the on-camera remote commander trigger flash does go off during the exposure. Depending on your distance to the subject and other factors the trigger flash is not likely to contribute much to the image but technically it is still there even if you have it set to "off" in the RC Mode panel.

    Separately from whether the commander is in "off/TTL/Manual" you set the intensity of the trigger to low, medium, or high - take some test shots with a small object close to the camera and in frame, you will see it is illuminated at different levels by the commander flash even it is set to "off" in the RC Mode controls. I usually have it set to "off" and on "low" intensity so you get minimal illumination from the trigger. Bump up the intensity to "medium" or "high" if your speedlight is having trouble seeing the trigger flash and failing to go off.
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  6. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    Real Name:
    John Griggs
    I did not know that, thanks.
  7. LowTEC

    LowTEC Mu-43 Regular

    I take photos of my fish tank many times a week, i can ensure you the trigger light does NOT flash during exposure if you set it to "off" in rc mode. Not even a slight hint of flash reflection from the trigger flash
  8. RobWatson

    RobWatson Mu-43 Hall of Famer

    That's what I see as well (usually). One can set the pop up flash to TTL (and set compensation) as well as set it to manual to get the little (or alot) of fill light as well. Pretty flexible!

    Once the RC mode is on the flash control panel is reached by pressing OK (not through the MENU - stumped me for a while) when the pop up flash is raised in the up position (this one still gets me occasionally).

    As mentioned above the TTL preflash can be set to lo/med/hi so if you are having trouble triggering an off camera flash check the level and bump it up - fixed for me so now I just leave it on hi. I think it helps metering accuracy when set to hi but I have no clear proof.
  9. Sammyboy

    Sammyboy m43 Pro

    Oct 26, 2010
    Steeler Country
    +1 ...... What LowTEC said.
  10. RobWatson

    RobWatson Mu-43 Hall of Famer

    With RC mode on and the pop up flash set to OFF on the E-M5 is most certainly does fire to signal the off camera flashes to do their thing but it does not fire during the shutter open portion of the exposure. Shoot into a mirror to convince yourself. What you will see is a bit of light that looks like the pop up is on but it is the flash well past being on and well into going dark. The flash pulse is not instantaneous but takes a while to drop in intensity levels that will not be visible.

    This means it is quite possible that there will be some light from the pop up in RC mode (set to off) that still impacts the image provided conditions are right.

    The image below shows the "after glow" of the pop up in RC mode but off.

    Note the pop up flash output level is very low if there is not an off camera flash so be sure to set up fully when testing this residual glow effect.
  11. RobWatson

    RobWatson Mu-43 Hall of Famer

    The only real problem with TTL + bounce (or manual for that matter) is the power levels do drop fairly quickly with distance so ones flash may not have enough output to properly light the scene. It can be tricky to determine if such is the case - would be nice if flash units had a warning light that indicated the last flash was at max power!
  12. fin azvandi

    fin azvandi Mu-43 All-Pro

    Mar 12, 2011
    South Bend, IN
    Well, I recall doing some tests myself (although not into a mirror) and concluded that the pop-up flash on my E-P3 was contributing some amount of light to the image due to how the shadows were cast. Perhaps I was just seeing what RobWatson describes. In any case it didn't seem bright enough to affect exposure, although I suspected it might appear as a catch light and that could detract from the appeal of the otherwise wonderful RC flash system. I'll try it again in front of a mirror if I have time tonight.
  13. RobWatson

    RobWatson Mu-43 Hall of Famer

    RC off but still on - fixed

    Just to wrap this up a bit along with some other comments from this thread.

    E-M5 with FL-LM2 as RC controlling a FL-300R (channel A TTL). RC mode with FL-LM2 set to off and lo power level (that is the signalling power level). I used Nokton 25mm F0.95 @5.6 - manual exposure 1/125 sec and ISO 200.

    First shot shows ambient with no flash to show the majority of the light is from the flashes (pretty exciting composition don't you think?). The subject is actually me reflected off a big window of my office so maybe not so clearly seen but a highly reflective surface. The hanging cord on the right is from the window blinds and is coincident to the glass surface.


    Next with the FL-LM2 raised showing the light still present during exposure even though RC mode has it set to OFF. Note the bright spot ~center frame.


    Next with one piece each of Roscolux 27 and 85 gel filters over the FL-LM2 to pass only NIR. This shows there is no impact on the exposure from the FL-LM2 but the RC control of the FL-300R still works just fine with only NIR light present.


    I measured the spectrum of light from the FL-LM2 +/- the Roscolux just to see how much and what "color" the light was present.


    Vertical axis is uncalibrated intensity. Horizontal axis is wavelength in nanometers. Red trace is the flash spectrum. Blue trace is the NIR filtered spectrum showing very little white light and not too much attenuation of the NIR lights.

    So if you still have troubles with a bit of fill from the RC commander then try a bit of filtering on the commander! Many photo shops have Roscolux gel filters for very low prices. I got several "books" with 100's of colors and diffuser samples from DTC Film Lighting & Grip Equipment Rentals in Bay Area Since 1983.
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  14. Clint

    Clint Mu-43 All-Pro

    Apr 22, 2013
    San Diego area, CA
    Real Name:
    When shooting macro shots the commander flash can contribute a small amount of light to the photo. Other than that, relatively no effect as the others have stated and Rob demonstrated.

    Many people prefer manual or TTL depending on what they think works best for them. I often like to shoot in manual as I have consistency across my photos. This only requires that once you like the exposure that the flash to subject distance remains the same in all of your shots.

    Other times I know I can't maintain the consistent flash to subject distance so I use TTL. TTL is something you have to ride the Flash exposure compensation (FEC) and/or the camera exposure compensation (EC). On some cameras if you adjust the FEC +1 and EC +1 you end up with a +2 exposure on your subject. I much prefer to keep the two compensations separate from each other.

    Either method can take some time to get good at, so just stay with it.
  15. RobWatson

    RobWatson Mu-43 Hall of Famer

    I'm think I need to retract the "after glow" comments ... as someone pointed out and I also see the commander flash does fire during the exposure (even when off). Set up using second curtain and note that the commander fires to signal the remote flash to trigger - this is during the exposure.

    In such cases were the commander light levels are not desired I think the NIR filter is the way to go (presuming TTL cable or radio triggers, etc are not viable options).