Sigma flash woes

Since my Pentax AF 540-FGZ flash began acting up a couple of weeks ago, I've been considering other flashes to replace it. Both Sigma and Metz have alternatives sporting the same functionality and output power. Today I gave in to the shopping lust and grabbed a Sigma EF-530 DG Super, which was a good 500 NOK (90 USD, 50 Euro/GBP) cheaper than the Metz.

Well at home, I subjected the flash to some tests. Exposure looked nice on both K20D and K-7 and P-TTL seemed to work as it should. But alas.

As you know P-TTL actually requires two blinks for each press of the shutter button. One blink to meter, one to expose the shot. So the flash needs to be sufficiently charged for two blinks before communicating "ready" to the camera. The Sigma reports "ready" when charge is sufficient for one blink. Which means that the camera can be fooled into metering for flash, but receive no output from the flash when the actual exposure takes place.

I discovered this by taking a series of shots with the K-20D. The first two shots were correctly exposed, but then followed three or four completely dark frames, and at last one correctly exposed frame with ambient light only. I waited 30 seconds to let the flash recharge, and repeated the series while watching with the camera away from my face. First there came two exposures with double-blinks. Then came three exposures with one blink, and at last a long exposure without flash. The three single-blink exposures turned out black.

So back at the store, I did a test series right there for demonstration. The salesperson sighed. "Worst thing is," he said, "I don't think your flash is faulty. We've seen this on Sigma flashes in combination with Canon as well".

I was offered to return the flash without any cost, but chose to trade it for a Metz 58 AF; spending the additional 500 NOK. Naturally, I asked to test the Metz before committing the money, and this flash behaved as expected. All P-TTL flash exposures correct.

Lesson learned.

Oh, and the Metz is still a good 1000 NOK cheaper than the original Pentax AF 540-FGZ, in case you wondered... :-)