How do you read and interpret the footage and aperture guide on the back of an electronic flash?

Question

I have an SLR camera that i bought a flash for. I do not know how to read the guid on the back. It is a Promaster FTD5400 flash. Also, does the guide matter when using the through the lens metering?

Answer 1

The amount of light reflected depends on distance to the flash. Set the guide for the ISO film speed and the aperture vs distance is displayed. This is for manual setting of the camera. If your camera has a focal plane shutter, be sure and use a speed slow enough so that the entire film can be exposed by the instanteneous flash, this can be a problem if you have additional light sources, such as outdoors.

An automatic flash meters the flash is measured at the strobe not the camera. In this case you pre-set the camera aperture, and the thryistor in the flash will quench the light after the exposure is reached.

The cameras automatic functions must be defeated to use an external flash. TTL metering takes its reading while the mirror is still down, therefore it never sees the flash during the exposure when the mirror is up. Some cameras have an OTF or off the film meter that can work during the actual exposure but usually they coordinate with a special connection to the flash to quench the light rather than trying to close the shutter. Without the flash being quenched, there is no way it can get the shutter closed to block additional light.