What’s Your Preference?

JeannieK · #1 (**permalink**) 05-21-2010, 12:34 PM

Sorry if this may seem like a dumb question.

I've just purchased the 430 Canon flash for my Canon 400D. With that I am using 18-55mm lens. Most of my photography is done in AV mode. I must say I have not tested out my flash properly as I have been reading he instructions. It's quite a lot to grasp and understand.

Just as a quick one, I mounted the flash onto the camera, set it to AV mode f5.6 and that was that. Put the flash on and ETTL displayed. I took a photo in my bedroom of not anything specific but I focused on an object. I pressed the shutter button, flash went off but it took a while for the shutter to finally release. Eventually when it didn't I pressed the shutter button to stop taking the photo. Ther photo was not blurred or anything but why did it take so long to take the photo and why did I have to press the shutter to for it to actually stop taking the photo. Could it be because I was indoors, the shutter speed was obviously very slow, even with the ISO increased to 1600. At first it was on ISO 400.

Please excuse my ignorance. I do need to practice but there is quite a bit I don't understand. I'm trying very hard.

Would appreciate some feedback.

i speak in math · #2 (**permalink**) 05-21-2010, 01:15 PM

I can't explain the shutter, unless it was so dark that it calculated a multi second exposure time. Maybe you can post the photo with the exif intact so we can see.

The reason it wasn't blurred is likely because there was no light making it to the sensor. It was so dark that taking a regular photo would be pitch black. However, there was a brief instant everything was illuminated with your flash. That was recorded, but nothing else. So the flash makes it appear like you're shutter speed was very fast.

This is how people capture water drops in midair or lighting

inkista · #3 (**permalink**) 05-21-2010, 09:47 PM

An external flash unit is not like a pop-up flash or a P&S flash. You have to learn how to use it, and the way the camera thinks you're going to use it by default is drastically different from the "Add enough light so I can take a picture, damnit!" scenario most people start out with.

A bit of background information (if this doesn't work for you, you can also try the EOS Flash Confusion section of the so-called EOS Flash Bible):

When you take a flash photo, you're actually combining two separate sources of light:

The ambient or available light, which is what you have without the flash.
The flash illumination.

Those two sources of light are independent of each other, and you can balance them out against each other any way you like. You can have most of the illumination be from the flash and very little from the ambient--which is how you get those black-background only-what-the-flash sees exposures, or you can have most of the light be from the ambient, with only a little bit of flash to "fill in the shadows"; this is called "fill flash". And anything in between. Unlike ambient photography, you can have any number of "right" exposure combinations.

In Av and Tv mode, the assumption by the camera is that you want to do fill flash. So if you're in Av mode, that means the shutter speed is going to be set to something very close to what it would have been without flash at all, and only a little bit of light is going to come from the flash. This actually makes sense if you're outside in the daylight, and someone's backlit, and you want to light up their face to match the background. But in a low-light situation, where you plan on having more flash illumination in the image than ambient, it's not the correct assumption. There are a few ways to "fix" this.

The easiest is to just put the camera into "P" or green-box full Auto mode instead. The assumption in the auto modes is that you're going to be using flash like you would for your P&S: more flash than ambient is required, and you plan to handhold the camera. You lose all control over the flash/ambient balance, but you'll get your exposure.

The second is to use the Custom Functions on your camera (C.Fn 03: "Flash synch speed in Av mode" -> 1/200s) to tell it that while in Av mode, the minimum shutter speed you want to use is 1/200s. This will push the balance towards the flash end of the spectrum, rather than the ambient end. But again, you lose all ability to control the flash/ambient balance.

The third (and best) way is to shoot with the camera in Manual mode, and control the ambient/flash balance exactly the way you want to with aperture, iso, shutter speed, and FEC.

Then, you get off e-TTL and put the flash in Manual, and control it with aperture, iso, shutter speed, flash power.

Then you get the flash of camera, and control it with iso, aperture, shutter speed, flash power, and flash distance.

Then you get multiple flashes and go hog wild.

Sobriquet · #4 (**permalink**) 05-23-2010, 10:13 AM

A couple of really good books that would fast track your understanding are available one is called Captured by the light but this is really focused on Wedding photography. Another is something like On camera flash techniques for digital wedding and portrait photography.

I suggest you move into the scary realm of M as you use AV you have a pretty good understanding to begin going into Manual. You can use AV mode to let the camera get you an approximate setting remember that you need to keep the shutter speed below 1/250 or 1/200 for that flash unless you are in HS mode.

The thing that tripped me up at first was not understanding why my images where getting overexposed as the camera sets the 1/200 and so other things need to be stopped down like aperture and turn your ISO down too. (Unless at night and you want to balance ambient and flash)

What your camera did was to expose as though you had no flash and that is why you need to go M.

Then learn to bounce!