OMD severe flash exposure problem

Started Apr 11, 2013 | Discussions thread
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clengman Senior Member • Posts: 1,911
Re: OMD severe flash exposure problem

photofan1986 wrote:

So, to the people's demand, here are some more controlled test shots.

All Canon 50D shots were made at FEC 0.0, Olympus OMD shots at FEC 0.0, too, unless otherwise noted. Also bear in mind that those were shot in a dimly lit room, and as high shutter speed has been used, there is barely no influence from ambient light, for the purpose of this test.

First, a simple shot, with mixed dark and bright tones.

50D, Evaluative metering, Focus point on the bird. Bird properly exposed, if slightly dark (highly reflective object).

50D, Evaluative metering, Focus point on the lion. Lion properly exposed.

Observation: As you can see, the actual focus point does have influence on the overall exposure.

Now, the same with the OMD.

General exposure, focus on the lion. Lion underexposed, and not reflective subject.

Observation: moving the focusing point to a darker and further subject changes nothing to the overall exposure.

Next test. Changing the metering mode on the OMD.

In this test, I did not change anything to the framing, just shot the same subject while changing the metering mode. First picture is focused on the bird, then the focusing point is moved to the lion.

Centre weighted average, focus on the lion.

Spot metering, focus on the bird.

Spot metering, focus on the lion.

Observation: Oh, surprise! Not only the metering mode did not change anything to the flash exposure, but moving the focusing point to the important subject did not do anything as well.

In every one of these pairs of images, the one with focus on the lion is just slightly, but without a doubt brighter than the one with the focus on the bird. You don't see it?

Conclusions to this:

- Changing the metering mode does not affect the flash exposure. Of course, when there is ambient light, sufficient shutter speed and iso speed, changing the metering mode does affect the ambient light exposure and as a result the final image. But with flash light only, there is no change.

- Moving the focus point does not change anything to the final exposure. The TTL flash exposure is calculated on basis of the general scene, and not a particular area selected by the focusing point (like Canon does for example).

Solution to this particular scene? FEC +1.0 or more.

Next test: how do framing changes affect flash exposure?

To be continued...

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