Sigma Em-140 Macro Flash help needed
Has anyone here got a Sigma EM-140 ? I recently bought one to use on a Pentax K-5 with Tamron 90mm lens. I'm having a few difficulties getting exposure correct. I though TTL would be a lot easier than this. All my test shots are over exposed by quite a margin.
I set the camera to P mode (although I've also tried Av mode) and noticed that the lens set a flash sync speed of 160th sec. The manual for the Pentax says the flash sync speed is 180th sec. I don't know if this mismatch is a problem of if there is a work around apart from me manually underexposing by 1/3 stop to compensate for the exposure. I still get a large percentage of shots over exposed even when I reduce the flash power on the EM-140.
I used a ring flash set up years ago with a Canon set up and don't recall it being this tricky, the E-TTL exposure there was more or less spot on. This is very frustrating as I like the K-5 and would like to get this sorted. Unfortunately the manual for the Sigma flash wasn't that comprehensive. I wondered if I was doing anything wrong ? I set the flash unit to TTL and expected the flash to tell the camera how much to expose the test shots at F11. I found that unless I really stopped down to say F32 that the test shots were over exposed.
Any helpful suggestions welcomed. I'm new to this so it's quite possible I've missed something.
I'd expect the flash is not compatible with the Pentax through the lens metering. Pentax uses a P-TTL system where there is a pre-flash where exposure is measured, followed the main flash. The time between the two flashes is quite short so it appears there is only one flash.
To test your P-TTL, use the built-in flash and install a Pentax kit lens or DA prime, and turn on the 2 second self timer. When you press the shutter release, you will see the pre-flash and then 2 seconds later you will see the second flash. Then you can see if this works with the Tamron mounted and then turn off the built-in flash and use the Sigma flash.
This should tell you what's causing the problem.
Have you tried adjusting the FlashExposureCompensation in your camera to help tone down the light intensity?
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