Explosure compensation for flash

[kbreit]

I just got a Canon 350D last night. I put it on full manual mode and started shooting. I've been using the exposure indicator to judge the amount of light (is this the proper usage)? One thing I am noticing though is that if you enable the flash, the camera doesn't adjust the exposure indicator to what the flash will produce. How do I compensate for the flash if it doesn't compensate?

[etaf]

why have you put it on manual mode????
I would simply use the other modes, Av, Tv or P depending on what you want to achive.
The flash will then work with those settings although will set the shutter speed, i think theres a thread here on how those settigns work.

[Jesper]

The built-in light meter always measures for the available light (not for the flash!).

So in Av, Tv and M mode, you set the aperture, the shutter speed or both and the light meter will tell you how the settings relate to the available ambient light, even if the flash is up.

When you press the shutter button, the camera actually very quickly flashes two times: the first flash is to measure the flash exposure, and immediately after that it fires the main flash at the strength required to get the right exposure. So the camera automatically fires the flash at the strength required to get the right exposure. You don't need to compensate anything. If you deliberately want the flash to under- or overexpose, you can use Flash Exposure Compensation (FEC).

You can read everything you want to know about the Canon EOS flash system here: http://photonotes.org/articles/eos-flash/

[kbreit]

Great explanation guys. In everyone's experience do the Tv Av modes give pretty good results, or do you normally stick in M?

[robertwgross]

I sense somebody who has not read the Canon EOS flash sticky.

I know it is a lot to read. I keep reading it over and over.

---Bob Gross---

[tim]

why have you put it on manual mode????
I would simply use the other modes, Av, Tv or P depending on what you want to achive.
The flash will then work with those settings although will set the shutter speed, i think theres a thread here on how those settigns work.

Etaf,I don't think your understanding isn't quite complete enough to be giving advice.

kbreit, M mode is perfect for flash photography where the flash is the main light, Av/Tv/P is best when you're using the flash as fill. Exposure compensation is irrelevant in manual mode, what you need is flash exposure compensation. Best read the camera manual and the EOS flash sticky, experiment, then come back and ask questions.

[Jesper]

Etaf,I don't think your understanding isn't quite complete enough to be giving advice.

kbreit, M mode is perfect for flash photography where the flash is the main light, Av/Tv/P is best when you're using the flash as fill. Exposure compensation is irrelevant in manual mode, what you need is flash exposure compensation. Best read the camera manual and the EOS flash sticky, experiment, then come back and ask questions.Tim has it exactly right. If you want to use the flash only to fill in shadows etc., use P, Tv or Av mode. The camera will choose the shutter speed and aperture combination for the ambient light, and the flash will make the dark shadows a bit lighter.

If you want the flash to be the main light source, set the camera to M mode. What shutter speed you choose doesn't really matter, as long as it's slower than the max flash sync speed. I usually set it th 1/200s, which is the max sync speed on my 10D. Note, it doesn't matter if you choose e.g. 1/100 or 1/200s. The photo will not become a stop brighter at 1/100s in this case! When you use the flash as the main light source, the exposure will happen during the very short time that the flash is on, not during the whole time the shutter is open. Choose an aperture setting that gives you the desired depth-of-field. The camera will automatically adjust the flash output (i.e., the flash will be brighter if you choose a smaller aperture or less bright when you choose a larger aperture).

As I and Tim said before, use FEC if you deliberately want the flash to over- or underexpose.

[tim]

Tim has it exactly right.

Heh heh, 6 months ago I was asking if an SLR could take video ;)

What shutter speed you choose doesn't really matter, as long as it's slower than the max flash sync speed. I usually set it th 1/200s, which is the max sync speed on my 10D. Note, it doesn't matter if you choose e.g. 1/100 or 1/200s. The photo will not become a stop brighter at 1/100s in this case!

The main thing changing the shutter speed will do is set the exposure of the background, in conjunction with the aperture - ie as if there was no flash. The flash will illuminate the foreground like Jesper said. Be aware though, if there is any light on the subject in the foreground and you choose a longer shutter speed (eg 1/30th as opposed to 1/200th), you could get "ghosting" around the main subject, kinda like a halo.

[kbreit]

Oh cool, my questions have been answered. I'll read the stickies and then go around and do some experimenting.

Kevin

[Hellashot]

why have you put it on manual mode????
I would simply use the other modes, Av, Tv or P depending on what you want to achive.
The flash will then work with those settings although will set the shutter speed, i think theres a thread here on how those settigns work.

From my use of the camera, Tv & Av modes do not account for the flash. Only P mode meters for the flash it'll throw.

[Jackal]

M mode is perfect for flash photography where the flash is the main light, Av/Tv/P is best when you're using the flash as fill

P mode doesn't provide fill flash. Isn't it just Av and Tv?

[tim]

P mode doesn't provide fill flash. Isn't it just Av and Tv?

Don't know, i've never used P, you could be right.