"flash for dummys" question...

[shortcake]

I can't believe I can't figure this out.

I have a 30D and a 430 EX.

When I try to use the flash in ETTL mode, it automatically
1) selects a shutter speed of 60 for P mode.
2) In TV it uses the widest aperture possible.
3) In M it tells me I'm under exposing even when clearly the flash has enough juice to give me a shot at 200 fps and F 4 or whatever (decently lit room indoors).

How can I get the flash to fire a bit brighter? I think it's called the Flash Ratio? For example, I want to shoot at 200 fps and F8 in a situation where I know the flash can handle it, I just don't know how to get it to do that!

Please let me know if I'm not clear and I'll try again. Thanks!

[samsen]

Did you try EV compensations?

[shortcake]

Samsen - Do you mean exposure compensation? Yes, but wouldn't that change the whole exposure of the picture? I want a properly expose picture, just to use more flash so that I don't have camera shake or moving subjects.

[TeeJay]

...For example, I want to shoot at 200 fps and F8...

200 frames per second? :confused:

[PeaPicker]

Read this http://www.photography-on-the.net/forum/showthread.php?t=171657 :)

[tim1960]

Shortcake,

I have the 20D and just recently received the 430EX flash. I have not encountered this problem. I'm able to change the settings. Not sure what is going on with your flash.

[shortcake]

TeeJay - Oops! What I meant was shutterspeed of 1/200th of a second.

peapicker - I will read and see if it answers my questions, thanks.

tim1960 - I thought maybe I don't know how to change the settings. Do you think something is wrong with the flash itself?

[steved110]

Check out this LINK (http://photonotes.org/articles/eos-flash) for some good information about Eos Flash.

You can summarise a lot of this by reading the following post which I made on another thread and copied here:

COPIED:

with ETTL flash, the camera does a very brief 'pre flash' to meter the scene, then sets the main flash to expose for what the camera decides is the subject. when this has been exposed, the flash cuts off.

A second exposure takes place also, the shutter speed and aperture you set alow for exposure of the background. The more light you let in thru the lens, the better the background will be exposed. if you let little light thru, the subject stands out against a very dark background, the longer the exposure the lighter the background becomes.

this is why it is easier to use the flash in P mode - the camera sets a sensible shutter speed to expose for the background, while using ETTL to expose the subject properly.

If you shoot in Av the camera will leave the shutter open long enough to expose the background as well - so you get a subject outlined by flash, nice and sharp, but also with motion blur etc because the shutter is open for a longer time.

Shooting in Tv is limited by the flash synch speed, high speed flash is possible with some speedlights but this reduces the flash's power ( range)

What a lot of people do is shoot in manual, set the aperture to get the dof you want, and the shutter speed to cope with motion blur etc depending on the effect you want, and rely on the camera to meter the flash properly. You can dial in exposure comp for the flash too if you don't like how it turns out. I rarely use high speed synch, and normally have my shutter speed set at the inverse of the focal length plus sopme more for luck. 1/200 seems to work well for me most of the time.

It does take a bit of practice to get used to flash photography, and to use it in a way that flatters the subject. the on board flash is not that great, I use it more for outdoor fill if I don't have my speedlite along. the nice thing about digital is that you can practice all you like!
__________________

[Curtis N]

How can I get the flash to fire a bit brighter? I think it's called the Flash Ratio? For example, I want to shoot at 200 fps and F8 in a situation where I know the flash can handle it, I just don't know how to get it to do that!Camera in Manual mode, shutter at 1/200 (actually you could go as fast as 1/250), aperture at f/8. Ignore the meter in the camera. It's measuring ambient light, which is not part of the equation in this case.
Flash in E-TTL mode. Adjust Flash Exposure Compensation (FEC) to get the exposure you want (the instruction manual for the 30D tells you how). Check your histogram and adjust accordingly.

[Bob_A]

Follow the advice Curtis has provided and all will be well :)

[shortcake]

Aha!

steved110 and Curtis, I think you guys explained it for me, thanks! I think what I am trying to do can only be done on the M setting, so that's what I need to play with. I will definitely try 1/200 with F8 - that is exactly what I want to use to start. And the explanation of why the camera selects a slower shutter speed by default helps too; at least now I know WHY it is doing that!