Originally posted by nscott Hi Ole,
Thanks for your reply.
This flash has TTL but not P-TTL. I guess that is not good enough?
I have the manual, which has the guide numbers. However that will not allow for very spontaneous photography!
Thanks,
Nick
I just looked at the manual for your flash on
PENTAX Digital Cameras and DSLRs - Official PENTAX Imaging Web Site. It does have a manual mode, which could be used with your K-m.
You're right. TTL mode requires that the camera have the flash sensor built into the mirror box of the camera and that the camera be able to communicate with the flash when enough light has reached the film plane. This is done during the exposure. P-TTL uses a pre-flash to allow the camera to measure the light reflected from the subject, before the exposure. All recent Pentax dslrs lack such an internal sensor. I believe that a couple of the original *istD series cameras did allow TTL flash, but your K-m does not.
Short of a true p-ttl flash, you need a flash with the sensor built into the flash unit itself. There are many examples of this, including the Vivitar 295HV and the Pentax AF280T.
When using any flash not specifically designed for modern dslrs, trigger voltage is critical. This is the voltage present across the sync terminals when the flash is fully charged. Some older flashes have trigger voltage as high as 300 volts, which is more than enough to fry the electronics in your K-m. I believe that all Pentax flashes, even the old ones, are safe, but dont' take my word for it. Measure the voltage with a digital voltmeter before using a flash. The trigger voltage should be 10 volts or less.