Setting a flash to an f number?

dan_yorkshire

dan_yorkshire

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Dan
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Hi everyone,

Still trying to master flash for daylight use and have a number of
different methods I am trying out so I can pin down my own routine.

Time for what is probably a really basic question but how do I set my
hotshoe flash (SB600) to an f/number?

I.E For fill flash some tutorials say to measure the ambient light and then
set the flash at two stops lower..... therefore if you measure the correct
exposure at f8 @ 1/125 I would need to set the flash to f4.

At the moment I think I am achieving this by using TTL and dialling the
flash compensation to -2.0, but may be totally wrong.

If I have the flash in manual mode, how would I set the flash to f4.... is
it just 1/4?

Cheers in advance

Dan
 
Any help from the afternoon crew?
 
If you set the flash in manual mode then you have to measure the daylight/flash output with a meter and adjust till you have the balance you want. TTL does all the hard work for you - and just works most of the time. Dial in flash compensation till you get the effect that looks good for the picture you're taking - regardless of what the books say!
 
I'm not an expert but heres what I do.

Firstly, it depends what mode your camera is in. In Aperture priority mode then the flash will meter as fill in flash. In Manual mode the flash will fire according to what you've set on the camera.
Both these will be limited by your sync speed (1/250 more than likely).

For portraits for example, I'd use Aperture priority and dial in perhaps -1 (or two depending on situation) of Flash compensation - this should be set on your flash gun. This is usually enough to give decent fill in flash.
 
You can't set the flash to f/4. You set the camera to f/4 and depending on all the other factors, the flash delivers the right power ouput.

1/4 is quarter power.

There's nothing wrong with using auto for fill flash, although it's useful to know what's happening and doing in manual will teach you that.

Whether you want -2 stops on auto depends on various things, quite often simply on the effect you want. On manual, bear in mind that flash is very distance sensitive so once you've set the power output for a particular shot, if the subject distance changes you'll need to readjust it. When you're close for a portrait say, even one foot either way can change things a lot.

Auto flash is great for this - it does all the fiddling for you and I find it's much easier to moderate the flash/ambient balance by tweaking the +/- compensation than the trial and error than is often involved in resetting the power output. Usually that is, it depends on how you like to work. In the end, it's just different ways of doing the same thing.
 
Older flashguns allowed you to set aperture values for a given ISO. I used to set my Metz CL-4 to two stops under for fill-in flash with good results. These days TTL makes life a lot easier and you just dial in the compensation as mentioned previously.
 
Cheers everyone,

Read a few more websites after I asked the question and soon realised that when using a light meter you can test the strength of the flash and tweak to make it two stops lower than the ambient light.

Took some test shots today and starting to get the hang of it.

Using in either Av mode or full manual and with TTL using the flash compensation to get the ratio correct.

Cant see much difference in the TTL mode and the TTL-BL fill mode, maybe there isnt.
 
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