Over Powering Daylight with Strobe

Stephen Eastwood|Beauty and Fashion Photographer | Tutorials





Below is a chart of a sky taken
outside at about 2pm in october (today) it was shot first straight all at 100iso,
all at 250th of a second which is the typical sync of many of todays dslr’s
you may have to adjust to suit a faster or slower sync speed. The first set
to the left was straight from the camera facing the direction but not at the
sun, it was to the right top corner, shot at f- 4.0, 5.6, 8.0, 11.0, 16.0, 22.0
the last shot you see the sun in the shot, the second set (middle) was straight
from the camera with a .3Neutral density and a Circular Polarizer on the camera
and was shot at f- 4.0, 5.6, 8.0, 11.0, 16.0, 22.0 the last shot you see the
sun in the shot. the last set was facing away from the sun (sun at your back,
overhead) shot with the same .3ND and CP on the camera. here is a link to larger
shots with all shooting data http://stepheneastwood.com/tutorials/skychart/skychart.jpg
you pick the sky color you want and see what setting you are at, remeber it
is better to have more power than less, and you can always adjust your shutter
from 1/250th down to brighten up a bit while maintaining the same flash power
on the subject.

How is this useful? well now you know what exposure for
the sky to look how you want it, the flash will need to be tested with the modifier
you want to use at the distance you want to be at. Set up your flash/modifier
and meter for the maximum power setting at the given distance. You will need
to have as much power as indicted by the f stop in the first row, or to shoot
wider open to reduce depth of field look at the options in row two and three
and remember that you now need to account for a .3ND and CP which means your
flash needs you need 1 stop more light to account for the .3ND and the CP is
variable but has a filter factor Between 2.3 and 2.8 (approx. +1.3 stops) so
best to account for 2 stops. What does that mean? it means if you have a strobe
that can shoot at f 22 with all modifiers at the distance you choose, you will
shoot at f16 but if you put a ND and CP on your camera it will reduce the flash
effectively by 2.5-3.5 stops so your flash can really only effective compete
in this scenario at f5.6-8.0 So to have enough power to block out the sun you
may need a flash powerful enough to shoot at f45 to f64.

All light modifiers (softboxes, Beauty Dishes, Octobanks,
Diffusers) eat up some light, some are more efficient than others, so you need
to test with the modifier at the distance you want to work out to figure the
real light. here is a chart from alienbees about how much light they put out
at a given distance with certain modifiers, as to its accuracy I am not aware
but I trust them to be fairly accurate. I have nothing for or against alienbee
but I am happy to show that they have numbers and I believe they will back them
up, so if these numbers work for you than all is great of not you would need
more power from alternatives, Hensel, Elinchrom, Speedotron, Profoto, Broncolor,
and white lighting all offer more powerful battery powered options you can explore.
Edit, whitelightning has since added th zeus line of pack and head strobes in
1250 and 2500 ws power units, they can be found here http://www.alienbees.com/zeus.html
. They are more powerful than the monolights and well priced and as such will
be more powerful than the below monolights.

some shots where some of this was evident you can check
the link I posted on the first page of this post, everything was shot with both
a ND and CP on the lens at all times. It was shot for a Tutorial dvd on lighting
and this topic was just one section of it. http://www.plasticmagonline.com/misc/mva_beach1

Stephen Eastwood

http://www.StephenEastwood.com

Below is a copy of a response I gave from another
post about overpowering daylight as well.

OK, lets say the correct exposure for a typical
sunny day is f16 at 1/100th at 100iso.

You want the background dark, lets say three stops
under exposed, so you need to start by upping your speed, but many current
digital SLRs are limited as are some medium formats, so lets say you max
at 1/200th flash sync speed. that gives you a correct exposure for the
background at f11 at 1/200th at 100iso.

Now you can make the background dark by setting
your f stop to f22 and the background is two stops under, but maybe you
dont want to shoot at f 22 or more.

So now you place a Circular Polarizer on the lens,
that can adjust you from 1.5 to 3 stops bringing your proper exposure
to 1/200th at f4-f8 depending on how much you cut the light. But in order
to get the background dark three stops you would still have to shoot at
f11-f16 again you may not want to be there but rather shoot at f 8 or
even f5.6 so you add a ND 1 stop 2 stop or 3 stop to the lens, lets say
you start with a 2 stop ND filter, that can give you the following proper
exposure

100iso 1/200th f5.6 for a three stop under you
shoot at f16

now add a Circular Polarizer and dial it down to
a proper exposure or 100iso 1/200th f2.8 for three stop under shoot at
f8

Since you are actually adding a lot of ND and CP
to the lens, you still need enough power from the flash to shoot as iff
they were never there. So you still need to meter a flash at f 22 or more
to over power the sky and subsequently overpower the fact that you have
3-4 stops of ND/CP on your lens.

It is always better to have some more ND than
you will need and more flashpower than you need since you cannot create
more ND or Power, you can of course shoot at a great depth of field, numerically
higher f stop or slightly underexpose a raw in processing if you shoot
digital and shoot raw, but that is not a great way to start off, its better
to do it the correct way to start.

Could always go out and set an f stop of lets say
f 8 shutter of 1/200th put on the ND/Polarizer you need to get the background
dark enough for you and then and turn the flash up till it looks good,
thats how I learned, and still do it.

1200 ws from a profoto, elinchrom and/or hensel
in a large silver lined SB with internal diffuser may be pushed and get
about f 16-f22, without internal diffuser maybe 1/2 – 1 stop more. This
all depends on what you want to shoot at f stop wise. A beauty dish without
grid will spread enough for a full body at 6 feet, a beauty dish will
overpower daylight at 10 feet at about f 22 or slightly higher for a white
silver gains about 1 to 1/12 stops over that.

Now if you want to have a little more fun, bring
some gels for the lights, I most often use 1/4 to 3/4 blue for the lights
which if white balanced for that on the model the background goes warm,
or reverse and use warm on the model to get a blue cold look to the background,
and if dark enough you can start to have a moonlit color begin. Of course
you may need even more power for this as you are now cutting down the
lights power with gels. Also works great on ringflashes

Stephen Eastwood

http://www.StephenEastwood.com

┬ęStephen Eastwood 2008 www.StephenEastwood.com
www.StephenEastwood.com/bio
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od.com/Tutorials

About photographers1

Stephen Eastwood Fashion and Beauty Photographer and Retoucher based in NY/LA/Ft. Worth TX http://www.StephenEastwood.com Current Canon Explorer of Light.
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One Response to Over Powering Daylight with Strobe

  1. cna classes says:

    well written blog. Im glad that I could find more info on this. thanks