Rented 580EX — Need quick tutorial

Pindy

I have rented a Canon 580EX and a Fong Light Sphere for the week and have never used an outboard flash in the past. Essentially, what do I need to know about using a flash vis-a-vis exposure? There is no manual and the Canon manual with my 30D assumes a level of experience I cannot claim.

Should I just set my exposure settings as normal and let the flash do the rest? I'll be outside, mostly using it as a fill flash. For indoors, when there's clearly not enough light to NOT use a flash, how do I deal with exposure when the light meter tells me it's WAY too low?

Finally, What's the deal with flash sync and shutter speed? Something about being able to sync up to 1/250s. I could use a plain English explanation of this.

Many thanks

patch29

The 580EX manual can be downloaded from Canon.

cmason

Pindy wrote:

I have rented a Canon 580EX and a Fong Light Sphere for the week and have never used an outboard flash in the past. Essentially, what do I need to know about using a flash vis-a-vis exposure? There is no manual and the Canon manual with my 30D assumes a level of experience I cannot claim.

Should I just set my exposure settings as normal and let the flash do the rest? I'll be outside, mostly using it as a fill flash. For indoors, when there's clearly not enough light to NOT use a flash, how do I deal with exposure when the light meter tells me it's WAY too low?

Finally, What's the deal with flash sync and shutter speed? Something about being able to sync up to 1/250s. I could use a plain English explanation of this.

Many thanks

OK the basics are this: the camera and flash are darn smart, when in doubt, trust them. However, when a flash is attached your camera settings behave a bit different. If you put the camera in 'P" mode, it will fire the flash for balanced exposure. My experience shows it does a decent job with fill, often a bit strong. Aperture and shutter priority work differently: they set the camera for the scene exposure, and use flash for fill. This means if the scene is dark, you will get a slow shutter speed, since it is metering the natural light. This can be confusing. Manual allows you to control.

I find the best shots come from reducing the power (EV) on the flash itself, so I use -1 2/3s often. I do this with nearly any mode: I use "P" when I just need the shot quickly and don't want to think. I use Tv outdoors, and M when I want a specific look to the image.

To understand this, read this:
http://www.popphoto.com/assets/download/821200311318.pdf


So when you take a shot, the shutter opens, the flash fires, and the light from it travels from the flash to your subject. So, if your shutter closes before the light has time to illuminate the subject, the subject will not be lit yet. This can be seen in extreme situations where there is low light, and you see half a picture, because the shutter was closing as the subject was lit, allowing only half the scene to be properly exposed.

The absolute must read on flashes, especially Canon flashes, is here:
http://photonotes.org/articles/eos-flash/

It will explain all these things better than I can.

pathfinder

There are a number of threads here on dgrin about the 580ex Flash. I do not generally rec using P with the 580ex, as the system ASSUMES and allows a shutter speed of 1/60th or faster, and will look like on camera flash.

Rent an ST-E2 to get you flash off your camera if possible.

Put your camera in Manual Mode and the flash in ETTL. You will have control of the ISO then, that you lose in Auto. You can then dial in plus or minus flash exposure compensation as needed.

Set the flash for High Speed Synch and you will be able to choose your shutter speeds as need . Shutter speed control will let you balance ambient versus flash, slower shutter speeds allowing more ambient light.

Some threads of interest

http://www.dgrin.com/showthread.php?t=32198&highlight=fill+flash+Pathfinder

http://www.dgrin.com/showthread.php?t=36457&highlight=fill+flash+Pathfinder

http://www.dgrin.com/showthread.php?t=50306&highlight=fill+flash+Pathfinder

http://www.dgrin.com/showthread.php?t=55691&highlight=ST-E2+candids

http://www.dgrin.com/showthread.php?t=4999


http://photonotes.org/articles/eos-flash/
http://photonotes.org/articles/eos-flash/index2.html
http://photonotes.org/articles/eos-flash/index3.html

If you read nothing else, read this brief discussion of the philosophy of the EOS flash system

http://www.dgrin.com/showpost.php?p=450610&postcount=6

Pindy

Brilliant replies—thanks all. I have much reading to do.