Flash Extender/Flash Bracket "Calibration"

I was wondering how super-tele users were calibrating the "aim" of

their flashes/extenders. With the flash above the lens, I find the

flash needs to be calibrated for different distances since the flash

is effectively shining down on the subject. So what works for 15

feet could be below the subject for 75 feet.

If I calibrate for a reasonable distance I find myself trying to

handle the flash bracket delicately so as to preserve those fine

adjustments. This is inconvenient and if the flash is off by a bit,

it is nearly impossible to re-calibrate it in bright daylight.

Any thoughts appreciated

Scott

<I>With the flash above the lens, I find the flash needs to be calibrated for different

distances since the flash is effectively shining down on the subject. So what works for 15

feet could be below the subject for 75 feet.</i><P>

This has me scratching my head a bit. I've never found this to be a problem, and I

assumed it's because the 'Better Beamer' is supposed to cover the FOV of a 300 mm lens

(on film or full-frame), and I use much longer lenses. In fact I've occasionally noticed the

flash bracket aimed a little too high or low because I failed to tighten it adequately, but the

images have always been evenly exposed. This is the case even when shooting with

extension tubes at a distance of about 3-3.5 meters (500 mm lens and converters).<P>

Is your lens a 300 mm or is it a longer focal length? Do you use the 'Better Beamer' or the

Lepp device ('FlashExtender', IIRC)? Where do you set the flash if it has a focal length

adjustment?

Hi Mark

I use a 500mm with a better beamer on a sb-800 flash set at 50mm (as per manufacturers advice). The flash bracket holds the flash a good 3 fet above the lens. Today I was shooting a great horned owl in a tree at a distance of about 70 feet and the flash was giving me back the underexpose warning. I had aimed the projected rectangle of the flash's light at my fridge door earlier in the day at about 25 feet. While you were answering this post I was trying it at about 80 feet on the shed in the backyard and the fridge "setting" was projecting way under the spot that lens was focused on.

I realise that if I were to set the flash at 105mm, I would get a wider rectangle of illumination, but the I lose the intensity.

Thanks for answering

Scott

Aha. Yes, I can see how that rig could cause a problem. I was assuming you had the flash

fairly close to the lens axis, but I guess you're trying to avoid the dreaded redeye/steeleye

syndrome.

Given that you need the couple of feet of extension, I'm guessing (again) that you'll need

to aim the flash fairly precisely at the subject when at close range (i.e., aim the flash down

relative to the lens axis), but for distant subjects you can probably mount it parallel to the

lens axis. I can't compute this in my head but out beyond maybe 40-50 feet (? yet another

guess) the FOV of the lens will be completely within the flash beam.

Some experimentation, such as shooting at a wall at various distances, would tell you

which ranges are OK with a parallel mounting and which need some down-angle on the

flash.

I use 550EX on Wimberley flash bracket, usually with Lepp's Project-A-Flash (I use Better Beamer for handheld).

I have never done any formal calibration, but if the subject is close enough (< 15 m) I have to tilt flash head down a little bit for the beam to get centered, exactly how much depends on the distance. I start with approximate position, then adjust.

It is hard to tell exactly what component is responsible for variation in angle, and I can imagine it can be different for different units of the same type.

Scott,

Are those chocolate covered donuts?

Bill

LOL, That's right! Grocery store, chocolat covered donuts with some maple "banding".

Scott

Scott,

I'll be right over. I'm a sucker for a donut. When I was a kid, the most fun thing was my dad taking me for a donut. Oops, sorry, off topic.

As Mark mentioned off axis flash is going to be extremely difficult to calibrate and control. If you care to look at the birds section of my website,"under construction", many of the small birds were made with a Better Beamer and the flash mounted directly to the camera.

Red Eye is a problem in some cases, more so on shorebirds I have shot than the small perching birds, I don't know why. But that set up gave me very few problems.

best,

www.billproudphotography.com/draft

70' at f4 = GN 280' at ISO 100. This is a non starter for the better beamer as it at best doubles the nikon's pathetic (140' MAXIMUM measured) output giving by my measurements a 1 stop improvement (GN = 200' @ISO 200). This means that at 70' you are about 1 stop underexposed IF you are on target.

BTW -- all the OEM flash specs are overstated, generally by about 1/2 a stop or more, by the mfgr.. A Metz 60 though with it's fresnel will indeed hit in excess of a GN of 300' at ISO 100! The 2H tele reflector on a norman head will yield a GN of 450' with ISO 100 and 300J of energy (300 Watt-sec) so a Q-Flash 400 Watt sec unit will likely hit a GN of 500+!!!! A Sunpak 120J with this reflector can hit nearly a GN of 300' at ISO 100..... I used the 300 Joule tele unit on a red-cockaded woodpecker at 40' using a 600mm f4 + 1.4X + 2X = 1680mm f11 (stopped down to f16) for a -1 stop fill flash. Worked like a charm but I had to aim the flash separately on a closer lightstand to get the 40' as the camera was at 70' for a better angle.

Grover Larkins<div></div>

I guess I should update this for the Godox-Witsro units. Measured GN (ISO 100) is about 200' with the standard reflector -- I'm currently measuring the Norman 2H with the Norman spacer but the tube socket in the Godox is recessed more deeply on the Godox than on the Lumedyne/Norman units and I need to make a longer spacer (I am going to try the Q-Flash tele flash tube spacer as it is longer and see). With the 2H and Norman spacer I am getting a 1 stop increase but it is clearly NOT optimized!

I'll add more later....