OMD severe flash exposure problem

Started Apr 11, 2013 | Discussions thread
Rriley
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Re: OMD severe flash exposure problem
In reply to photofan1986, Apr 15, 2013

photofan1986 wrote:

How do framing changes affect flash exposure?

In this test, I will shoot a similar scene with both cameras, in evaluative metering, the Canon will be set to FEC 0.0 and the Olympus to FEC +1.0, as we have seen previously that the camera underexposes by about one stop (or slightly more).

Framing 1 50D

Framing 1 OMD

Framing 2 50D

Framing 2 OMD

Framing 3 50D

Framing 3 OMD

Framing 4 50D

Framing 4 OMD

Framing 5 50D

Framing 5 OMD

Conclusion of this test? The OMD is very sensitive to framing changes, and is very easily fooled by highly reflective areas. The Canon seems to operate a brain connection with the photographer as the pictures look the way the photographer wanted them to be. I think it's black magic. To some people here it seems inconceivable.

Side effect: It's not always possible to just apply a positive exposure comp to the OMD, because sometimes even slight framing changes shift the exposure entirely.

Oh, by the way, the Canon has a secret weapon the Oly doesn't: it's called flash exposure lock. Pressing the blue star button on the back of the camera fires a pre-flash to measure the exposure on the selected focusing point and locks it until the shot is actually taken. Brilliant.

For those who say that the small clip-on flash on the OMD is not powerful enough to expose this scene properly, here is a picture at full power in manual mode.

Last test: flash exposure inconsistencies.

Ok, so now we know that the camera underexposes by at least a full stop and that it is very sensitive to framing changes. But how does it behave on a static subject with almost no framing changes?

Trying every shooting mode, I saw something interesting.
In A mode, the camera behaves as we noted before.

A mode, 1/60, F 4.0, 200 ISO.

But when I switched to P mode, with very similar settings, but F 2.8 instead, here's what I got.

Aha! Perfect exposure with NO FEC! So have I actually found something?

No, unfortunately.

I shot the next picture just changing the framing ever so slightly. Bam! underexposure again.

Final Conclusion?

Well, controlled test or real life, it's clear that the Olympus flash system is suffering several issues, besides lacking some powerful features like FEL.

- It underexposes by at least a full stop.

- It is very sensitive to reflective subject in the framing, at the point of making it totally unpredictable.

- Changing the metering modes does not change the flash exposure.

- Changing the focusing point does not change the flash exposure.

All in all, a pretty disappointing performance for a supposed modern and well evolved flash system.

My first goal was to determine what was wrong with the camera or the settings. All that before investing in an expensive, external flash unit. And after many trials, I came to the conclusion that the flash is not faulty (I tried my dad's EPL-3 flash with the same results), but that the camera will behave the exact same way with any TTL flash I'll put on top of it. That is, quite unexpectedly in my opinion. Up to the point that I wonder if I'll not simply skip the TTL setting, and go back to prehistoric time where people used manual flashes or auto thyristor flashes (I have no problem with those for some specific uses, but TTL is (or should be) a pretty major evolution in the flash system).

flash on anything isnt perfect, there will always be ways to f it up, and each system is different, and has its own inherent weaknesses.

As for this stuff about metering modes, a camera flash combination will always try to adjust the exposure to 18% grey, so in a dark scene such as the ones where the cabinet takes up more than half the frame it will overexpose. As you would know the scene is often not 18% grey, so compensate. Metering will try to make dark scenes bright and pale scenes dark, so it does have an effect

metering will always try to adjust flash output to 18% grey, with a dark cabinet its going to overexpose and have a hot spot in the middle if you are too close without a diffuser

ok these are only test images but:-

It seems like you are using a highish shutter speed, that isnt going to help as it tasks the power of an already weak flash, especially like these small flashes in TTL mode.

Images lit purely by direct flash look like cr4p, so its better to make IS work for a living and drag the shutter a little, which has a tendency to mix ambient and flash.

My FL36 used to behave exactly like this, my FL50 can power across a 10m room in TTL mode. When it comes to TTL mode the problem IMO is power.

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Riley
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