Canon Speedlite 244T ISO Settings Help?

[skim422]

I currently have a Speedlite 244T working with a Canon T50. I have only used it on the 400 ISO setting with the camera at 400 as well for night photography. I was wondering what the difference between the flash settings at 100 and 400. Like is one brighter than the other? Also, what would happen if I used a different ISO setting on the camera than the flash? Like 400 ISO on camera (and film) and 100 ISO flash setting? Any help would be appreciated cause I'm pretty new at this! Thanks!!

 

[Big Mike]

Welcome aboard.

I don't know how that particular camera & flash work together for flash exposure. It might be that the light is measured TTL (through the lens) via a pre-flash. That's basically how modern flashes work...but with this old unit, the flash might have a built-in thyristor circuit or something like that. (you could probably Google it).
Anyway, the difference between ISO 100 and ISO 400 is two stops. (4 times as much light). So if you set ISO 400 on the camera but ISO 100 on the flash, the flash will give you two stops more light than you need. If you set the flash to ISO 400 and the camera/film to ISO 100, you will get two stops less exposure from the flash.