Quote Originally Posted by roberttalbot View Post
ahhhh I see. Makes sense in regards to when you say "how long the flash fires" and you're saying that the TTL is able to read the distance, so the TTL capability on the flash knows how far the subject is from the flash therefore applying the particular length of time the flash fires?

This is very interesting, and this makes the most sense to me in our exchange. I need to go out shoot in different light situations in the TTL mode, and wait for development. For me I need to know as much as I can before shooting with a new "tool"
Your ability to link will be limited on APUG until you have been around a bit longer and made a few more posts. That was instituted to help stop the robo-spammers.

TTL doesn't read distance. It just measures how much light from the flash has bounced back from the subject. When enough has bounced back to properly expose the film, it turns off the flash.

The distance affects how much light from the flash reaches the subject and how much light bouncing from the subject reaches the camera - if you are far away the light spreads out more.

Are you using the flash as your source of light, in situations where there isn't enough ambient light to work? If so, the TTL flash will work great.

If you are trying to use TTL flash to "fill" or balance lighting in situations where there already is enough light to expose the film, you will most likely just get frustrated. The focal plane shutter on the camera limits your flash use to speeds of 1/50 second or slower. This means that apertures need to be small and/or films need to be slow in order to expose properly for ambient light. If you do that though, the flash will often need to be too close to the subject.

In addition, the ambient light will tend to confuse the TTL metering, and cause the flash to shut off prematurely.

If you are going to use fill flash with a camera that requires a 1/50 second shutter speed for flash, most often you need to use the flash in a fixed position, in manual mode, using either a guide number calculation or a flash meter.