Flash photography

Mystwalker · Feb 7, 2008

I feel like an idiot. I did "Strobist" tutorials and still can't figure out how to use my 580EX II.

Strobist to me went into a lot of detail while I just want to get light in a darker environment - this is for starters. Yeah, rank newb :grumpy:

I upgaded to a 30D with 17-40 f/4 and am taking (trying to) pictures in rooms with normal overhead lighting. The flash on 30D, sometimes, was not enough. I thought the 580 had enough power to hit target at 100+ feet - do not remember exact number.

I normally shoot in Tv mode (need faster shutter to catch daughter running around) - have tried "M" with better results, but quality still nowhere close to what I see here or anywhere. Even resorted to the "P" mode and still came up with some very dark or completely dark pictures.

Have tried new battery in 580EX. Tried to point straight up to bounce light, and also pointed directly at daughter (she did not like that).

Have gone back to my 50 f/1.8 for now - best buy for $70 :thumbup:

Any advice appreciated.

Thanks.

Mike_E · Feb 7, 2008

Have you read this?

http://planetneil.com/tangents/

Mystwalker · Feb 7, 2008

Thanks. Have not seen that. Am reading it now.

Mr_Bester · Feb 7, 2008

I don't know about the 580EX, but I use my 540EZ for candids of my daughter in normal sized rooms. It does depend on the room size.

I usually put the flash on the stand at about 6-7' and bounce it off the ceiling. It worked great for Christmas morning. I did chimp a bit and put my wife in the room the night before to get the correct exposure. I have to shoot everything on manual though. Usually 1/30th to 1/200th @ f7.1 or 8 or so. I think the flash was on 1/16th power, zoomed out as far as possible without the wide angle adapter flipped on.

I use the gadget infinity wireless and didn't miss any shots at Christmas.(Luckily, the only time I had problems getting one of the 2 to fire was when I was practicing a still life).

Lately, I've been planning on setting 2 flashes up in opposite corners of the room and bouncing for a bit of crosslight.

You could practice with anything and get set readings for each room. If you are shooting with the flash on camera, it won't work as well because the distance from flash to subject will change.

Dug

Big Mike · Feb 7, 2008

The Strobist stuff is great, but that is manual flash. It sounds like you just want to figure out your flash and the E-TTL metering technology that it (and your camera) is capable of.

Your flash will act differently, depending on what mode you are in. In Av or Tv, the flash will act as fill, and it expects that your main exposure will be from ambient light. So if it's not very bright, you will run into problems with long shutter speeds or a limited max aperture.

When you use P mode (or heaven forbid, the green box)...the camera will probably choose a large (or max) aperture and a shutter speed around 1/60. That combination will probably not be enough for an ambient exposure but the flash will output enough light to expose your subject. This should work for you but the results may not be ideal either. Because you may have little or no ambient exposure, it might look like your subject is in a dark cave...or a deer in the head lights.

When I use flash, I put the camera into manual mode. I set the aperture for the DOF that I want (keeping in mind that the flash has to work harder when the aperture is smaller). The flash will automatically adjust it's power to suit the aperture that is set. The shutter speed actually doesn't matter for the flash exposure....as long as it's under the max sync speed (1/250 on your camera). The shutter speed is used to control the amount of ambient (background) exposure. A longer speed is more exposure. So with a longer speed, you can expose some of the background (if there is ambient light) and the flash will expose the subject. It's actually two exposures...all flash photography is.

You can run into problems if there is too much ambient exposure because the subject may get double exposed and the ambient one may be blurry. This is called ghosting. It can be used to show motion...but usually you want to avoid it.

With all that said. Sometimes the E-TTL metering of the camera & flash...isn't what we want it to be. This may be because the subject is very reflective and tricks the camera. This is why we have FEC (flash exposure compensation). Because the flash will set it's power to the aperture you are using...the exposure would be the same at F2.8, at F4 and at F11. But if you want to change the exposure, just dial in a positive or negative FEC (Probably easiest to do it on the camera).

The great part about E-TTL metering, is that you can bounce the flash off of something...and it will still output enough power for your exposure (as long as it's not too far to bounce). The 580 is very powerful and should be good in most situations. If it's too dark, it's probably something with your settings.

For a lot (and I mean a lot) of in depth reading about Canon flash...see THIS.