Sigma Em-140 Macro Flash help needed

Started Jul 15, 2012 | Discussions
Sandhurst Junior Member • Posts: 39
Sigma Em-140 Macro Flash help needed

Hi All,

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.



Pentax K-5
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T Evergreen Forum Member • Posts: 95
Re: Sigma Em-140 Macro Flash help needed

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.

cmantx Senior Member • Posts: 1,394
Re: Sigma Em-140 Macro Flash help needed

Have you tried adjusting the FlashExposureCompensation in your camera to help tone down the light intensity?

 cmantx's gear list:cmantx's gear list
Sony SLT-A57 Sony a77 II Tamron SP AF 70-200mm F/2.8 Di LD (IF) MACRO Tamron SP AF 90mm F/2.8 Di Macro Tamron SP 150-600mm F/5-6.3 Di VC USD
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