Beginner with speedlites.

Im new to speedlites. I understand channels and ratios. I use (2) 430ex and (1) 580EX , along with the wireless

transmitter. Im having difficulty understand the manual zoom ranges. im trying to set up a basic three flash shoot. I

was under the impression that i would not have to manually set any zoom. the field guide im reading tells me i have

to set the zoom on each flash. is that true? what do you do if your using a lens outside the maximum 105 mm

maximum coverage. If someone has the time to give me a real world readers digest version of how the zoom function

works on the speedlite it would help me alot. i think im making this more difficult than it really is. thanks

Anthony

Check out Chuck Gardner's tutorials on Canon speedlights here at http://super.nova.org/DPR/

<Chas>

The zoom setting on a speedlight is expressed in millimeters, typically so that it will correspond to the field of view

that a lens of that same focal length will have when used on a traditional 35mm ("full-frame") camera. So, if you put a

50mm lens on a full-frame DSLR or SLR, you'll see a certain angle of view, and you'd want your strobe (when

mounted on the camera) to throw light in a pattern that roughly matches that field of view.

<br><br>

When you put that same lens on a cropped-sensor camera (one with the APS-C-format sensor more commonly used

by most people at this point), the effective field of view is reduced. That 50mm lens is giving you the field of view more

traditionally associated with a 75mm lens. So, your speedlight - if it's set to 50mm - is throwing away a lot of its

energy lighting up areas that won't even be captured by the camera. Some newer devices (like Nikon's SB-900) are

aware of what sort of camera they're on, and compensate for the sensor size as they do the math.

<br><br>

Why does this matter, when you're talking about using - as you are - your speedlights off-camera? Because it once

you understand the field of view issue, you understand how to set your strobe's zoom value to create a puddle of light

that's big enough to do the job, but not so wide that you're wasting battery power. Especially when you're needing all

the light you can get for a given situation, the tighter the zoom (seen as a higher mm number), the more efficiently

it's throwing light into a given area.

<br><br>

If you have a zoom lens, you can actually do some simple predictive tests: stand with your camera in the position

where you'll be placing the strobe, and look at the field of view... zoom the lens so that you're seeing the bounded

area where you actually want the light to fall, and make note of the focal length. You can use that as a guide for the

zoom setting on the strobe. Keep in mind that the strobe things in full-frame fields of view... so if you're using a

cropped sensor camera, a 50mm field of view would equal a 30mm soom zetting on the strobe, etc.

<br><br>

Or, you can use a very wide angle lens, and shoot pictures of a big wall... and do a little experimenting. Set the

speedlight to various zoom positions, and move it back and forth from the wall as you trigger it. You'll see a distinct

pattern on the wall (sort of like shining your car headlights on the side of a barn). That will help you develope a solid

gut sense of how the speedlight casts light at various zoom settings.

<br><br>

Lastly: much of this thinking goes out the window if you're using light modifiers (umbrellas, reflectors, softboxes,

snoots, etc). The optimal zoom setting on the speedlight is then driven by how you want the light modifier to catch

and modify the light. If you're using a speedlight-friendly softbox (say, one of Lastolite's EzyBoxes), you'll probably

want the speedlight set to its widest possible setting, to make the light as even as possible. Bouncing out of

umbrellas, or off of a flat reflector, may NOT call for the widest setting, if you're trying to constrain the spill just a bit.

That's something you need to play with.

<br><br>

To reiterate: if you're using your strobes off camera, the precise match between the focal length of your lens and the

strobe's zoom setting really doesn't matter. You're using your strobes to cast a pattern of light, and deciding how

tight or wide that pattern should be is a matter of creative choice and practicality. There's no point throwing a pattern

so wide that the camera will never see some of it, but too-narrow a pattern can cause light to fall off on parts of your

subject. Once you're off-camera, the actual measurement in mm isn't really worth fussing about... it's all about what

that pattern actually looks like in the end results... adjust to taste!

I'm assuming you will be using light modifiers for the shot (umbrellas / soft boxes).

The zoom function and light modifiers have polar opposite functions: the first is to narrow / concentrate the

light beam so that on a bare flash you can evenly illuminate objects further away; whilst the second is to

produce as large a light source as possible - for wrap around and softness.

If you use a light modifier and the zoom facility together, this will have the effect of only illuminating a

percentage of the light modifier - which defeats the reason for using a light modifier in the first place -

producing as large a light source as possible (unless there are special effects you are looking for).

I set my SB800s as wide as possible when using an umbrella - in fact I leave the diffusion dome on the SBs which

automatically sets the zoom to 14mm - nice wide beam (at the expense of distance)

It only makes sense for the flash to match the lens if it's mounted on the camera and firing straight ahead.

Otherwise, you have to use your brain. :-)

You should set the zoom to cover the angle you need it to cover. For example, if you're firing a flash into an

umbrella, you want it to cover the umbrella with minimum spill.