Flash Question - Power Ratings vs. F-Stop Ratings

[earthling]

Hello!

I am looking at buying either a Phoenix D91-BZS or Vivitar DF200 to supplement the flash on my Canon A620 and just wondered if someone could clear up a flash question that I can't figure.

Some flashes, like the Vivitar DF200, list various power ratings that you can switch between (full, 1/2, 1/4, etc.) while others, like the Phoenix D91-BZS, list f-stop ratings to gauge intensity. Does this mean that the Phoenix flash will intelligently meter and expose the picture as it sees fit? If it is acting as a slave flash, how does it generate this metering info? How does this correspond to the f-stops listed? :confused:

As you can tell, I am a tad confused on this one. Any help is greatly appreciated!

(...and I apologize if this question is answered elsewhere. I looked! Lots of stuff on specific flashes, but nothing on this general question I could see...)

Look forward to your informed and informative responses. :D
- Travis

[cwphoto]

Adjusting the f-stops is an automated way of attempting correct flash exposure according to your lens aperture. Prior to modern Through The Lens (TTL) flash metering, a small sensor on the body of your flashgun was used to measure the reflected light.

It's effectiveness is a little hit and miss as it doesn't take into account subject distance or luminance - but it works well if you're aware of these limitations.

[earthling]

Thanks, CW!

I believe that clears things up. I like the sounds of the flexibility of the Phoenix D91-BZS in this case then. I am still a little fuzzy on the implementation of the theory in so far as whether I will be manually changing the f-stop meters on the flash (since it is a slave flash without a direct connection to the TTL metering) or whether it is a "smart" flash of some kind that learns these things.

In any case, you've put my mind at ease that I'm not losing versatility by going with the Phoenix D91-BZS despite its not having a simple full power, 1/2 power type setup.

Thanks again (and feel free to add any other relevant comments or advice on the topic)...

- Travis

[cdifoto]

Thanks, CW!

I believe that clears things up. I like the sounds of the flexibility of the Phoenix D91-BZS in this case then. I am still a little fuzzy on the implementation of the theory in so far as whether I will be manually changing the f-stop meters on the flash (since it is a slave flash without a direct connection to the TTL metering) or whether it is a "smart" flash of some kind that learns these things.

In any case, you've put my mind at ease that I'm not losing versatility by going with the Phoenix D91-BZS despite its not having a simple full power, 1/2 power type setup.

Thanks again (and feel free to add any other relevant comments or advice on the topic)...

- Travis


For what it's worth...I had the Vivitar DF200 and it was rather underpowered. It also was difficult to use effectively.