Better Beamer and Canon 580 Flash....

[grover_larkins2]

Folks, it seems like time to put the inevitable Better Beamer type flash

extender claims to bed again here.... About a decade ago I tested all the then

available flash telephoto extenders out there -- Tory Lepp's Tele-flash,

Walt's Better Beamer and the no longer available Metz Televorsatz for the Metz

60 and the Sunpack extender for the old 611 all against the Norman 2H

reflector.

 

The bottom line was that the 2H gave an honest 2 F stop improvement over the

standard Norman/Lumedyne/Quantum reflector and all the others gave you a 1

stop improvement over the flash's best effort at all zoom lengths.

 

I recently re-tested the Better Beamer on a Canon 580 EX -- at 100' and ISO

100 using a Sekonic flashmeter (718). Here are the results:

 

With the 580EX at 105mm of reflector zoom the Guide Number was 200 (F 2.0).

 

With the Better Beamer on the flash and the flash zoom set at 50mm the GN was

171 (F 1.7) at its best (I checked all extensions as there is about 1/2 an

inch of "adjustability" in the positioning of the fresnel supports on the

flash....).

 

With the Better Beamer on the flash and the flash zoom set at 105mm the GN was

280 (F 2.8) at its best (I checked all extensions as there is about 1/2 an

inch of "adjustability" in the positioning of the fresnel supports on the

flash....).

 

"Best" position in all cases was with the ears of the flash bracket even with

the flash's aperture.

 

Bottom line -- you can expect a 1 F stop advantage when using the Better

Beamer over the best your flash can do without it. The claimed 2-3 stop

improvement is misleading, it improves the situation, but not by the stated

amount.

 

Grover Larkins

[mark_chappell]

My own tests indicate about a 2-stop improvement (i.e., you can roughly double the range

that a given aperture will provide adequate exposure).

[Former P.N Member]

Given that the basic purpose of these devices is to concentrate the light the alignment is critical. My own (very unscientific) testing shows that it does this very well. See: <a href="http://rtope.com/flashtest/">http://rtope.com/flashtest/</a>

<p>

Note that the flash was set at 1/64 power for this test.

[karl_lehmann]

I have also tested this and I get 2 stops increase with the Better Beamer on the 580EX. Dick is right, alignment is critical (and can be a real hassle in the field!).

[mark_chappell]

<I>Dick is right, alignment is critical (and can be a real hassle in the field!).</i><P>

 

Minor alignment errors have very little effect if you're using a long lens (500 mm +). Around

300 mm, alignment is more critical, especially for the corners of the image.

[karl_lehmann]

The major problem with alignment in the field comes when you don't know where to expect your subject. Due to parallax the correct alignment varies with distance, especially when using a flash bracket. One method I've used is to strap a bright penlight to the flash head. You still get parallax error, but much less of it and at least it's consistent. It also allows you to focus!

 

I often use the Better Beamer at very close range (< 2m). With a small subject it gives much softer lighting than a bare flash, as well as 2 stops extra depth of field. You can preset the lens to closest focus and align for that, then focus by moving the camera ("rocking").

 

Incidentally, with perfect alignment the 580 EX/ Better Beamer combo will just barely cover 200mm (full frame). But I almost never use it below 300mm, the alignment is too touchy.

[grover_larkins2]

Given that I have measured this with a meter -- outdoors at night -- not with a camera during the day I'll stand by my numbers. Generally a 1/2 stop underexposure will be "visually ok" and from that you get about a 1.6-1.7 X light gain. I have also run calculations on the "Better Beamer" and, given overspill and imaging of the flash aperture at infinity, the absolute maximum gain available with the Better Beamer on a 580 EX set at 105mm is around 2X (check it out -- it illuminates roughly 25% of the area or a region corresponding to about a 200mm lens with the better beamer in use than the raw head set at 105mm does at 100'). The backscatter and overspill -- fresnel backscatter is somewhere between 1/2 and 1 full f stop (measured) and overspill is probably about 1/2 stop (guesstimated).

 

This puts you right at the measured gain of 1.4X or + one stop.

 

I did make a larger unit myself with the same focal length fresnel (but MUCH larger -- 8x10") and tested it and got nearly 1.75 stops of improvement (GN ~ 350) but there was ZERO overspill.

 

A longer fresnel (focal length of 12") and 8x10" dimension got me 3 stops but the image was a very hot spot and not useful for a lens w/fl less than 600mm -- and absolutely impossible to align and use!

 

Bottom line -- 1 f stop is what you get but it is convenient and useful....

 

Grover Larkins