FL-300R TTL issues

Started May 9, 2012 | Discussions
veesah
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FL-300R TTL issues
May 9, 2012

I'm testing an E-P3 & FL-300R combination to get a feel for Oly RC.

I noticed that hotshoe TTL and RC TTL don't calculate same flash output with RC FEC set to 0.00. Light output was much closer when I set set RC FEC to +3.0. Have I missed a setting somewhere, is this a peculiarity of the 300R or is this common among all Oly R strobes?

A few notes:

  • flash position was unchanged for the test above (just removed from hotshoe)

  • camera settings: manual iso, aperture priority, EC -2.0, FEC 0.00

  • camera config: EC+FEC off

micksh6
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Re: FL-300R TTL issues
In reply to veesah, May 9, 2012

veesah wrote:

I'm testing an E-P3 & FL-300R combination to get a feel for Oly RC.

  • flash position was unchanged for the test above (just removed from hotshoe)

And I guess, at this position flash didn't see RC signal. Normally FL-300R can see reflections from walls/ceiling. Probably not in this case.

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veesah
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Re: FL-300R TTL issues
In reply to micksh6, May 9, 2012
  • flash position was unchanged for the test above (just removed from hotshoe)

And I guess, at this position flash didn't see RC signal. Normally FL-300R can see reflections from walls/ceiling. Probably not in this case.

Flash definitely did fire - and I can see increasing power levels on multiple shots taken while increasing RC FEC to +3.0...

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micksh6
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Re: FL-300R TTL issues
In reply to veesah, May 9, 2012

If only part of RC signal is missed the flash will fire but will use wrong compensation.
Similar thing happened with FL-36R:
http://forums.dpreview.com/forums/read.asp?forum=1041&message=39762308

I would repeat the test making sure FL-300R is in line of sight of on-board flash.

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veesah
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Re: FL-300R TTL issues
In reply to micksh6, May 21, 2012

I'm not sure my problem has to do with line of sight. I've done a bunch more testing on this to try to figure out exactly what's going on. In my case, it looks to be TTL calculations getting confused from either TTL or RC pre-flashes. Details follow.

The following tests are with a 20mm lens at 2 - 3 ft distances from subject, with the goal being to fire flash on wall behind camera. Camera set to full manual exposure at -4 stops below current light levels. FEC set to 0.0. RC FEC set to 0.0. I expect the camera's meter to set flash power to reasonably expose for the scene.

  • Control: Flash on hotshoe, bounced backwards (FL-300R doesn't twist, so I used a piece of foam). Scene exposure was reasonable, as expected. This also confirmed flash power was sufficient for given manual settings.

  • Test 1: Take flash off hotshoe and hold directly upto flash controller (facing backwards). This blocks the controller light from ever reaching the subject. Camera works as expected, reasonable exposure.

  • Test 2: Hold flash 1 ft ahead of camera, still facing backwards and out of lens view. Camera under exposes, but 2 - 3 stops. This invalidates line-of-sight explanation.

  • Test 3: RC communication mode was set to LOW for previous tests, I switch to HIGH and try again. This time, the scene is practically lit by direct camera flash (i.e. flash controller!!). RC flash fired at a negligible power level.

  • Test 4: Use a piece of foam to block all light from flash controller from hitting subject. Result is a reasonable exposure from RC flash.

Conclusion: Camera has to send a signal for pre-flash so it can calculate apparent light levels before sending a second signal to actually fire the flash. It seems that at close ranges (

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ginsbu
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Re: FL-300R TTL issues
In reply to veesah, May 21, 2012

I regularly use a reflector to direct the on-board flash output away from the subject. I do this mainly to control the "bullseye" look in the eyes of my subjects, but I've found I get more consistent exposures with it.

Something I haven't tried is to use an IR-pass filter to cut the visible light output from the on board flash from contributing to the exposure. Lee makes polyester filters that can be cut for this purpose and aren't too expensive. Apparently exposed and developed negative film (like leader), or unexposed and developed slide film, will do the job too.

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micksh6
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Re: FL-300R TTL issues
In reply to veesah, May 21, 2012

veesah wrote:

Conclusion: Camera has to send a signal for pre-flash so it can calculate apparent light levels before sending a second signal to actually fire the flash. It seems that at close ranges (

What are your settings for E-P3 on-board flash in RC mode? You can disable on-board flash so it acts only as controller, without illuminating the scene.

I'm not very experienced with flash photography so I try to keep things simple. I don't use manual exposure, I use aperture priority mode, set EC to +0.3 for both shutter and flash and then rely on TTL measurement.

If flash has enough power for current environment this will exposure scene well, regardless of whether the flash is on hotshoe or operated remotely - there is no difference. That is when flash fully sees RC signal. I think if RC signal is partially blocked this may screw up TTL measurement.

It is possible that with manual exposure things work differently, I haven't tried.

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veesah
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Re: FL-300R TTL issues
In reply to micksh6, May 21, 2012

What are your settings for E-P3 on-board flash in RC mode? You can disable on-board flash so it acts only as controller, without illuminating the scene.

FEC + RC FEC: off

Group A: TTL 0.00
Group B: Off
Group C: Off
Camera Flash: Off
Flash/FP: Flash
RC Power: LO/HIGH (depending on the test)
CH: 1

It is set to not illuminate the scene. If the camera flash was contributing to the scene on purpose, it wouldn't have left the scene underexposed.

My best guess to how TTL may work is something like this:

  • Camera measures current ambient light

  • Camera asks flash to fire at known power level (eg: 1/32) and measures light

  • The difference between the 2 is the flash contribution. The camera can then calculate required flash level for proper exposure as a multiple of this contribution

  • Camera asks flash to fire at calculated power level

In the above, if the RC controller illuminated the scene during the 1/32 flash pop, it would mess up the calculation and cause the camera to calculate a final flash power which is insufficient for the current scene.

It is possible that with manual exposure things work differently, I haven't tried.

Ideally, I want to underexpose ambient by a stop or two and use bounce flash as primary. I've done this in aperture priority and in manual with Nikon CLS. This works perfectly fine with Olympus RC as long as flash is on hotshoe. The challenges I'm encountering are while using Olympus RC - which from the tests above seem to be as a result of design decisions of how Olympus RC technology works.

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veesah
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Re: FL-300R TTL issues
In reply to ginsbu, May 21, 2012

I regularly use a reflector to direct the on-board flash output away from the subject. I do this mainly to control the "bullseye" look in the eyes of my subjects, but I've found I get more consistent exposures with it.

Perhaps the findings from my tests can explain why you get "more consistent exposures"

Something I haven't tried is to use an IR-pass filter to cut the visible light output from the on board flash from contributing to the exposure. Lee makes polyester filters that can be cut for this purpose and aren't too expensive. Apparently exposed and developed negative film (like leader), or unexposed and developed slide film, will do the job too.

That's a great idea! I know Nikon sold a little thingie using similar IR filter ( http://www.bhphotovideo.com/c/product/410445-REG/Nikon_4905_SG_3IR_IR_Panel_for.html ) for their onboard flashes

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ginsbu
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Re: FL-300R TTL issues
In reply to veesah, May 21, 2012

veesah wrote:

I regularly use a reflector to direct the on-board flash output away from the subject. I do this mainly to control the "bullseye" look in the eyes of my subjects, but I've found I get more consistent exposures with it.

Perhaps the findings from my tests can explain why you get "more consistent exposures"

Yes, that was always what I suspected, but I had never done any specific testing to confirm one way or the other. I'm glad you've confirmed it for me.

Something I haven't tried is to use an IR-pass filter to cut the visible light output from the on board flash from contributing to the exposure. Lee makes polyester filters that can be cut for this purpose and aren't too expensive. Apparently exposed and developed negative film (like leader), or unexposed and developed slide film, will do the job too.

That's a great idea! I know Nikon sold a little thingie using similar IR filter ( http://www.bhphotovideo.com/c/product/410445-REG/Nikon_4905_SG_3IR_IR_Panel_for.html ) for their onboard flashes

Yes again. 4/3 folks have used the Nikon one with the Olympus wireless system, but it obviously won't work neatly with the clip-on flashes occupying the hot shoe.

Here are links to the Lee filters I mentioned:

http://www.bhphotovideo.com/c/product/102762-REG/LEE_Filters_87P3_3x3_Infra_Red_87.html

http://www.bhphotovideo.com/c/product/292664-REG/LEE_Filters_87CP3_3_x_3_Infrared.html
I think the 87 should work. Never tried it myself though.

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Mr.Ed
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Re: FL-300R TTL issues
In reply to ginsbu, Aug 14, 2012

Hi,

I am a new user of the OMD and an FL-600R. I am seeing the same issues with RC TTL consistently underexposing anywhere from 2 - 4 EV. Auto mode works a little better, but still underexposes around 1 - 2 EV sometimes.

I am searching the forums and find similar observations with the FL-300R and FL-36 with EP3.

In all those threads, I don't really see a final solution, and the discussions just died off with users resorting to adding +3 or +4 EV for TTL mode. But to me that is a hit and miss. It doesn't consistently need that compensation. There clearly seems to be a metering problem in the RC mode.

When the flash is in the hotshoe, it meters fine. it underexposes slightly, about .7 EV, but consistently, so I can just dial that in.

Anyone has a real solution to this? Is this an inherent problem with the RC system for Olympus?

thanks,
Ed

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veesah
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Re: FL-300R TTL issues
In reply to Mr.Ed, Nov 23, 2012

Anyone has a real solution to this? Is this an inherent problem with the RC system for Olympus?

My conclusion is that Olympus' implementation of RC is faulty - flash pops for purposes of communication between devices should not affect TTL calculations.

In my case, this means that I stopped using RC altogether - instead, I use manual flash with cheap ebay wireless trigger.  Alternatives is to to use wired TTL (there are cables available).

A less reliable alternative is to wrap some aluminum foil around the RC controller and bounce the light backwards - this minimizes impact, unless you are at high ISO.

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