[Eruditass]

here's a scenario....tell me what i can do
subject in front of camera facing left
off camera speed light camera left in TTL lets say its the key light shooting through a screen.
rim light coming in from behind subject camera right on a stand...this light is in manual or ttl, doesn't matter.


can i shoot the flash camera left in ttl remotely (lets say an af360) if i trigger it with an onboard flash?

Yes

and can I control the FEC from the remote flash from where I'm shooting from?

The left TTL one? Yes

does the flash have to be pentax of can i trip the remote flash camera left with the light on board?

I'm not sure I understand the question, can you rephrase? Many P-TTL (Sigma, Metz) can use P-TTL and be triggered wirelessly.

Meanwhile, if I want to make an adjustment to the rim light camera right, can I adjust the power of the flash by using the controls from the on-board flash or K5 body?

Only in a round about way. You'd have to dial in negative FEC (for the P-TTL on camera left) and increase the Aperture/ISO (decreasing the exposure time if you want to keep the ambient level the same). This flash also has to be in ignore preflash mode (S2 for YN)

not sure how this went from tethering....but I'm more interested in this anyway since this is what I grapple with day to day.

From what I've heard, P-TTL can be unreliable on exposures though, and that might be reason enough to switch. For me, if the subject is moving closer/further from the key light and I want the exposures to stay the same, I'd see if I could move the key light further away, if it will still be sufficiently soft, so the inverse squared law doesn't affect it as much or just deal with it in post. Perhaps not ideal, but it doesn't bother me for the savings, especially since I'll be processing those shots anyway.

[Deiberson]

Quote:
and can I control the FEC from the remote flash from where I'm shooting from?
The left TTL one? Yes

how do I go about doing this? can I control the FEC in TTL in the K5 body with my af 360 to the camera left? or do I need a 540?

or....do I need the af540 to be the commander on the K5 to control the flash to the left? this is where I get a little confused.

[Eruditass]

From what I recall, the FEC on the body will change the FEC of all P-TTL flashes. Is this not the case?