580exII focal range

Question, the 580ex2 allows you to change the focal distance of the lens your using to suit the flash distance.

when shooting with the flash off camera, does the focal range matter when in "M" mode?

Doesn't changing the power output +/- do basically the same thing as changing the focal distance of the flash head and also physically moving the light stand/flash around?

If I'm shooting with a 35mm lens, and the flash is 10-15 feet from the subject(a car) do I need to set the flash to 35mm as well or is adjusting the power output adequate enough, especially if I'm going to be moving the flashes around the subject...

The only thing that matters is flash-to-subject distance. When the flash is mounted on the hotshoe, the two (camera-to-subject, flash-to-subject) are the same.

Take the flash off-camera and you should calculate/adjust based upon flash-to-subject distance.

By the way, changing the output (+ or -) doesn't change the maximum output of the flash. If you're at the limit of the exposure distance, setting the flash to +1 stop won't increase the effective distance. I'm sure you know that, but you'd be surprised how many paid photographers I've run into that do it thinking it works.

As far as changing/zooming the head of the 580 EX, it doesn't increase the output either. What that does is concentrate the total output into a wider/smaller area to match your lens' focal length.

I'll reword this. The zoom method of the 580EXII simply changes the relationship of the plastic lens in front of the flash tube to change the size of the beam of light. You can test this yourself by taking photos of a spot on a wall thhat the flash hits with various zoom settings. It has nothing to do with the flash output per se.

So if you have a 100 mm lens and its field of view, there is not much reason to flash the light in a wider field of view because why light up things your lens won't image on the camera sensor? Conversely, if you have a 35 mm and you want the whole field of view to be lit up, you should adjust the zoom lens on the flash to project light in a wider area to match the field of view of your lens.

And you know the edges of the light beam are not sharp, so you have some leeway.

A little experimentation and some test shots will show you the capabilities and features of your speedlite. It is your job to adjust the settings on the speedlite to get the light to do what you want. You don't "have to" set the zoom head to 35 mm just because you are using a 35 mm lens. You can do anything you want.

DisrupTer911 wrote in post #6980249
Question, the 580ex2 allows you to change the focal distance of the lens your using to suit the flash distance.

when shooting with the flash off camera, does the focal range matter when in "M" mode?

Doesn't changing the power output +/- do basically the same thing as changing the focal distance of the flash head and also physically moving the light stand/flash around?

If I'm shooting with a 35mm lens, and the flash is 10-15 feet from the subject(a car) do I need to set the flash to 35mm as well or is adjusting the power output adequate enough, especially if I'm going to be moving the flashes around the subject...

The flash does not allow you the change the focal distance. What it allows you to do is to match the field of coverage of the flash to that of the lens when the flash is mounted on the camera. When the flash is off-camera, then it'll be hard to maintain the same FOV relationship with the lens unless the flash is the same distance from the subject as the camera is.

When you take the flash off camera, what you want to do is set the flash head zoom so that the flash coverage is at least the same or greater than the FOV of the lens. And that does not necessarily mean setting the flash to 35mm if you're using a 35mm lens. If the flash is closer to the subject than the camera is, you may need to use 24mm or even pull out the wide panel for a 14mm (or 17mm) coverage.

Another thing to note is that the flash head zoom is not normally adjusted to give you different levels of flash power. You zoom to match the FOV of the flash to the lens as was mentioned above. Of course, the power output will vary at different zoom positions so you will need to adjust the flash output power accordingly.

ah okay guys, thanks for that clear up.
I was afk for a while helping a family friend move, otherwise i woulda thanked everyone sooner.

I did try your test out against my wall and now it's clearer to me how the flash zoom works compared to lens FOV.

thanks everyone!