From: paul stenquist
On Dec 5, 2009, at 7:48 PM, Igor Roshchin wrote:


Sat Dec 5 17:27:17 CST 2009 AlunFoto wrote:

2009/12/5 Igor Roshchin <str at komkon.org>:
I wonder if that's a feature of the P-TTL mode, and if
so, - how to deal with that. It doesn't do a preflash, -
so, I don't think it really works as a P-TTL flash.

If it doesn't preflash it's not in P-TTL mode.

Are you using pre-A lenses on the camera? If so it reverts to
old-style TTL.

I just checked that. Picked up my 540 at the repair shop
yesterday, it didn't get to Antarctica poor thing...

Jostein

Jostein,

No, I've had this with 17-70 and 50-135. Maybe TTL with 540 FGZ
is worse than that with 500 FTZ?

Igor

Actually, the P-TTL performance of the 540 FGZ is relatively good, at
least for Pentax. I'm not very familiar with the 500 FTZ, but it's
always been my impression that it was a TTL flash, not a P-TTL? If it
was P-TTL capable, it would work with the newer cameras, and to the
best of my knowledge it can only be used in manual or flashj/auto
mode with the K10 and later cameras. But I could be wrong.


Depends on what is meant by P-TTL

According to the manual, the AF-500 FTZ has a Programmed TTL Flash mode where "The aperture and shutter speed vary automatically according to subject brightness" to give proper flash exposure. AF-500 FTZ P-TTL only works with some cameras.

I know it's not compatible with the K10D, and by inference probably not K20D or K7.

I wonder if part of the P-TTL function has to be embodied in the camera for the AF-500 FTZ, while AF-540 FGZ has all of its P-TTL function built into the flash?

That might explain why the AF-500 FTZ doesn't work properly with later cameras.

If you're having problems with flash, experiment. With digital,
that's fairly simple. And as I said, reflectors change the game plan
a lot. If you use a spill type reflector in a room with a high
ceiling, you're going to get minimal output. Today, I shot at the
mall with its 200 ft. ceiling, so I used a softbox diffuser rather
than a spill reflector or lumisphere. The right diffuser for the
situation is critical. Paul

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