advise needed

Hi
I am beginner but would like a external flash for my *IST DS.
1) I don't know the difference between TTL and P-TTL ? explanations ?
2) I saw that Pentax has two the 360 and the 550 (from memory), ans sigma has one one also (EF500)... how to choose. The purpose of the flash is first to take portrait indoor, and second outdoor photos.

Thanks a lot

Christophe

Christophe,

TTL is Through The Lens metering.
P-TTL is Preflash Through The Lens Metering. In this mode a small burst of flash occurs first, the camera judges the exposure and corrects the aperture before firing the real flash. Generally it gives better exposure, but does mean that you get two flashes (which confuses any "magic eye" cells for slave flashes).

The AF360FGZ is the most recent flash gun. You can purchase it for around £180 in the UK. It's a very nice, compact and powerful flashgun. I use this and a Metz 50MZ5 with my *ist-D.

The AF360FGZ is the only flashgun that has high speed sync - which is useful for outdoor fill in flash. The flash will sync at higher shutter speeds (I think 1/250s... will have to check the manual). It does also support manual, "old fashioned" automatic, and wireless (dumb slave and full control from an *ist-D only).

Hope that helps.
Matt