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03-21-2015, 10:14 AM   #1
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Pentax Flash Question

Hi Everyone,

I have a 645Z which doesn't work as expected with their own Pentax Flash in HSS when using the FEC from the flash. I would like to know anyone else have their Flash on your DSLR notice this problem, or this is isolated to the 645Z only.

Here is the my part of the story:

Just want to write a little more details, and hopefully that would be helpful for those who are interested to use the Pentax Flash PTTL system with the 645Z

- 645Z

Both allow you to setup the Flash in HSS mode as a Master Flash on Hot-Shoe or Controller mode.

The challenge I have with Flash compensation not working when making the changes from the flash

At 1/125 +1 FEC on the flash, it works. As soon as you start 1/160, the +2 FEC no longer kicks in.
At 1/125 +1 FEC on the Camera. Using 1/160 continue to accept the +1 FEC from the camera

Sadly, you can use -4 to +2 FEC from the flash if it works, on the camera, you are limited to -2 to +1

Translate this to a remote flash setup using my 360 II as controller and the 540 II as the remote flash. I am limited to +1 FEC from the camera, as the flash because of the HSS mode, which is very limiting, when compare to my Canon remote flash setup.

Read more at:

03-21-2015, 10:39 AM   #2
ScooterMaxi Jim's Avatar

Join Date: Jul 2009
Location: Minnesota
Posts: 1,501
I suspect the camera is indicating to you the maximum flash output - in reality doesn't have the power to go beyond +1 exposure control. It might be smarter than the flash in this regard.

There are better workarounds, IMHO, than relying on the flashes at hand / pTTL / HSS. Depending on the situation, use more flash power from another source(s) and an ND filter to get the right balance of ambient and torch. The larger flashes will give you shorter duration so no worry about freezing action if that's your concern. In any event, you'll tend to get more consistent results and quicker shutter response if you take pTTL out of the equation.

Even the second iteration of Canon preflash TTL isn't great (but is more consistent than the Pentax implementation in my experience). Many Canon wedding photographers avoid it due to the flash metering confusion caused by stark black and white contrast (I don't have a link handy but there's a dedicated website addressing the issues - and suggesting workarounds).

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