Fill flash (1 Viewer)

Hi

Can someone advise what kit might be best for Canon 40D and 100-400 Combo

for use in the field (tropical ) IF I was to consider it.

A lot of birds in CR are troublesome; tending to be black lol, and always perching against a white sky; I have been told fill in might help.
However being dumb how could this work at 30 metres + at 400mm?

Rich

You can use a Flash Extender (Better Beamer) to focus the light from a flash and increase the range. It is said to be good for adding at least a couple of stops, or doubling the reach.

http://www.birdsasart.com/accs.html#BEAMER

So, combined with a 580EX and used at f/5.6 and 100 ISO you could expect full illumination at (58 / 5.6) x 2 = 20.7m, if you could shoot at or below the sync speed. Since you only want fill, and not main light from the flash you would be down almost exactly 1 stop at 30m, which is a good starting point for fill.

So, yes, it could/should reach to 30m. However, if you need to shoot faster than 1/250 then you will run into problems as HSS loses power fast as soon as you start pushing shutter speeds beyond the sync speed of 1/250. If you go up just a small amount, to 1/320 the flash power will drop by about 1 stop and it continues to deteriorate the higher you push the shutter speeds.

That's the maths as I understand it. While I do have a Better Beamer, and have used it in the field with my 580EX, I have not undertaken any controlled experiments. Usually, when I use it, I dial in -2 FEC and pretty much let the thing do whatever it can to help the image. Typically I will use it to illuminate the shadowy undersides of BIF against a bright/backlit sky, so it ought to at least help out with your scenario.

I've just found a recent example, where I was having to shoot into white, overcast skies. According to the EXIF the distance is exactly 30m and I used the Better Beamer at -2 FEC for this shot. At 1/1000 I'm not sure how much help the Better Beamer was, but every little helps, I think. This was shot from the deck of a pitching boat, so framing was tricky and I was unable to fill the frame, but here is the unedited original and a version with a crop and minor tweaks.

Excellent info Tim, thx very much!
Rich

p.s. Of course, those calculations above were based on shooting at 100 ISO. If you bump the ISO then you gain roughly double the distance for every 2 stops you add. I say roughly because the inverse square law applies to point sources of light rather than flash heads with a combination of fresnel lenses to focus the light. I imagine that the rule will be close enough to get you in the ballpark.