Quick Flash-gun question..

Raider · 6 Oct 2006 at 19:24

Ok i've just got my 430EX up and running and i've been snapping away in the front room. Now I understand that in AV / TV mode, the camera exposes to the ambient light, then the flash flashes at whatever setting.

However in low light conditions, that means that the camera ends up taking exposures at around 0.3s at ISO 400, which is pretty useless at 50mm F8 even with the flash, as camera shake still shows up.

If I set it to manual mode and shoot it at ISO 200, 1/50s then it looks absolutely fine in terms of exposure.

So i'm just a bit puzzled about this default ambient exposure thing, as by default it'll always give you a long-ish shutter time. Where as I thought the whole point of a flash-gun was that you could use fast shutter times in low light situations. I can do that, but only in manual mode.

Am I doing something wrong? :confused:

FatPete · 6 Oct 2006 at 19:31

It confused me as well when I got my 580EX.

As you've noticed, AV and TV expose for the background (hence the low shutter speeds), and Program mode sets the camera between 1/60 and max x-sync speed, using the flash to expose for the foreground.

Manual also exposes for the foreground - I tend to use this mode now for the majority of my flash photography.

Take a look at this link - specifically the 'EOS flash photography confusion' section.

http://photonotes.org/articles/eos-flash/index2.html#confusion

AdWright · 6 Oct 2006 at 19:52

Beat me to it! That site's a great read for learning how to use flash effectively

Raider · 6 Oct 2006 at 20:04

Ta I'll give that a read.

Looks like full manual is the way forward for me! It seems quite forgiving too. Random apertures and ISO numbers seemed to produce the same result. I'm guessing the flash adjusts its power according to those settings.. :confused:

SDK^ · 6 Oct 2006 at 21:10

Raider said:
I'm guessing the flash adjusts its power according to those settings..

Yeah it does

I generally use 1/125 and F8 indoors and Av mode with fill-in flash outdoors

Raider said:
Where as I thought the whole point of a flash-gun was that you could use fast shutter times in low light situations. I can do that, but only in manual mode.

In P Mode the flash works with shutter at 1/60 - Flash sync speed.

Raider · 6 Oct 2006 at 22:34

SDK^ said:
Yeah it does
I generally use 1/125 and F8 indoors and Av mode with fill-in flash outdoors

In P Mode the flash works with shutter at 1/60 - Flash sync speed.

Using P Mode the camera seems to default to F4.0 and I can't seem to change it. Mashing the buttons that I normally do to change aperture / shutter time have no effect.. :confused:

EDIT, twiddling repeatedly to change the aperture I can reduce it to F8.0, but it's not constant. It's a bit odd..

AdWright · 6 Oct 2006 at 22:49

P is essentially an automatic mode, ie aperture and shutter speed are set automatically. However, you can change other settings such as exposure compensation etc (unlike fully automatic mode)