Light meter and pre-flash

Chernobog

Hi, everyone,
I have a little concern with my equipment:

Pentax K-1
Pentax AF540FGZ II
2 x Cactus V6 II
Sekonic L-308X

I would measure contrast of light with my light meter, but the flash shall work in P-TTL mode and it shoots a pre-flash, which cheats the light meter. Now I have to switch my flash on "M" mode and set the power directly on its body. Is it possible to design a test mode on the V6 II, with pre-flash disabled?

raychan

Thank you for the suggestion. I'll discuss with our engineering team for the possibility.

Chernobog

Thank you. I've read that it is a common problem with transceivers and TTL flashes. Only some high-priced light meters are capable to ignore pre-flashes. On my L-308X if find a solution: measuring the flash with shutter speed 1/15 s, it is able to see both the pre-flash and the main flash.

raychan

That's brilliant.

Chernobog

That's a quick fix ))
That works using the V6 II test button.
Triggering via camera shutter button, on the L-308X you have to set a reading time equal to 1/8 s. Such method is appliable only in indoor shootings, where ambient light is unimportant compared to the flash.

Chernobog

Hi, everyone,
did engineering team find a solution with these pre-flashes? Such problem makes the use of external exposimeter impossible when shooting outdoor, I should use a cheap set of triggers instead of V6 II.

Chernobog

I've tried to activate flash with my camera thorugh the mirror up exposure, and effectively at the first press of the shutter the pre-flash bursts, but the main flash doesn't. Maybe it will work with rear curtain sync.

But I'm searching for a methot to test the flash without pressing shutter, because I want to shoot with film camera also.

Chernobog

Hi, everyone,
meanwhile I've find the final solution to many problems:
"NOT TO USE CACTUS TRANSCEIVER IN ANY COMBINATION WITH PENTAX FLASH"

In my experience Pentax flashes are intended to be used on Pentax cameras only, foget the TTL pass-through.

First of all Pentax AF540FGZ II, a flash for 500 $, has a crappy hot shoe lock (it's entrusted to a very fragile tooth running in a groove), that perhaps will not break if used on a Pentax camera, but it will in few months if mounted on a Cactus V6 II, because the thicker rim of the V6 II's hot shoe mount and the resulting higher stress.

Because of Pentax pre-flash, that works even in manual mode (it's an artificial manual mode, the flash must always be set in P-TTL) is not possible to make measurements with a lightmeter.

Trying to trigger a Pentax flash causes myriad of other problems, that I'm not about to list.

Using two V6 II in combination with an expensive Pentax flash is an useless waste of money, I recommend to buy only one Cactus V6 II and one or more Cactus RF60X, such ensemble will work perferctly both in manual mode and TTL.