Outdoor Strobe - Shallow DOF - Bright Sun?

OK,

I've not yet taken my new studio stuff outside but just "thinking" through the process I'm curious on the approach you "lighting" pros would take.

Let us assume it is a partly sunny day and you want to take a nice family portrait. You have a portable system such as AB800's with a Vagabond. The goal is to get nice bokeh. For the sake of this discussion let us assume we are shooting with the 70-200mm f/2.8 IS on a tripod with an ISO of 100. The background is somewhat close so the goal is to blur it out.

If I assume correctly the fastest shutter speed I can obtain using the AB's is around 200 how do I get a shallow DOF and not blow out the sky?

ND Filters? Polarizers? Is that the only way?

Make sense?

Let's analyze...
Assume lowest ISO on your dSLR is ISO100...so in the sun the Sunny 16 exposure is 1/100 f/16, or f/1600 f/4 (for shallow DOF). With the AB flash there is not HSS support so you are stuck with 1/200 f/11. So the only way to get -3EV to permit opening the lens to f/4 is -3EV neutral density.

Yep, you jumped to the right conclusion!

Wilt wrote in post #2141667
Let's analyze...
Assume lowest ISO on your dSLR is ISO100...so in the sun the Sunny 16 exposure is 1/100 f/16, or f/1600 f/4 (for shallow DOF). With the AB flash there is not HSS support so you are stuck with 1/200 f/11. So the only way to get -3EV to permit opening the lens to f/4 is -3EV neutral density.

Yep, you jumped to the right conclusion!

OK, so now I need to research ND filters huh? What do some of you guys carry in your bag, for this type of situation?

taygull wrote in post #2141923
OK, so now I need to research ND filters huh? What do some of you guys carry in your bag, for this type of situation?

My own solution is to bring a medium format film camera with a long lens and slow film (inherently reducing the problem by both those things), and to shoot using lenses which have in-lens leaf shutters rather than focal plane shutters which are inherently more limited in synch speed with electronic flash.

Sometimes the classic wedding tool is far superior to the dSLR...this is one of them!

why not try using a 580EX flash??
you surely can get shallow DOF more easily!!

kenliu2610 wrote in post #2142110
why not try using a 580EX flash??
you surely can get shallow DOF more easily!!

Not enough power if I'm doing a family of 4...

taygull wrote in post #2142396
Not enough power if I'm doing a family of 4...

Can you satisfy my curiosity please? Set your camera in M at 1/1600, f/4, ISO 100. Turn your flash on, zoom it to 50mm and enable high speed sync, FEC at 0.

Half-press the shutter button and look at the distance scale on the flash. What is the distance reading?

I am not quite getting the thrust of this post.

If the given conditions are as posted "bright sun" and the desired apertures are F/2.8, why is a studio based electronic flash even in the mix (even at ISO 100)?

Seems like a reflector here and there, without flash, or the needed neutral density filters, would be a far more elegant solution (or even a small camera mounted flash).

Why force fit something when the stated contitions are already so accomidating?

Enjoy! Lon

A cheaper more practical solution is to go without strobes. Use light panels and reflectors as your primary lightsource. Now you can use whatever shutter speed you like. . For the cost of a moderately priced strobe setup, you could buy a couple 77"x77" panel assemblies and a reflector or two for adding some specular highlights (rim lighting and what not).

londuck wrote in post #2142570
I am not quite getting the thrust of this post.

If the given conditions are as posted "bright sun" and the desired apertures are F/2.8, why is a studio based electronic flash even in the mix (even at ISO 100)?

Seems like a reflector here and there, without flash, or the needed neutral density filters, would be a far more elegant solution (or even a small camera mounted flash).

Why force fit something when the stated contitions are already so accomidating?

Enjoy! Lon

You started fine, Lon, until you mentioned 'a small camera mounted flash'...which cannot be used at 1/1600! But your point is correct. why a studio flash when a reflector would do similar things, and not limit the shutter speed.

The disadvantage of reflectors is that in bright sun they too easily cause everyone to squint !

taygull wrote in post #2142396
Not enough power if I'm doing a family of 4...

Not enough?? I do this to take large group of people, just using my 580EX!!
It's 17mm wide. I fire up 580EX at ETTL(+1/3 EV) only at which I set the distance at 14mm.
The camera is about 10 feet away from the people. It was cloudy day on that day!!

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yep, it works well when you are not worried about DOF. I'm looking at more of a portrait shot instead of a snap shot. If you notice in my first post I was speaking of a sunny day so there would potentially be harsh shadows on the fact that would need to be removed.

taygull wrote in post #2144079
yep, it works well when you are not worried about DOF. I'm looking at more of a portrait shot instead of a snap shot. If you notice in my first post I was speaking of a sunny day so there would potentially be harsh shadows on the fact that would need to be removed.

Then maybe using a reflector will help...

Wilt wrote in post #2142653
You started fine, Lon, until you mentioned 'a small camera mounted flash'...which cannot be used at 1/1600! But your point is correct. why a studio flash when a reflector would do similar things, and not limit the shutter speed.

The disadvantage of reflectors is that in bright sun they too easily cause everyone to squint !

Wilt,

Thanks for catching that mistake.

But, certainly a studio type flash would be shackled with this same shutter speed encumbrance.

So, if you have to have F/2.8 (or F/4), and ISO 100, and a shutter speed of 1/1600 sec (or so), it would have to be a reflector, a near vaporizing intensity continuous light, or a flash with a high-speed sync mode.

The studio flash unit just is not going to cut it if all this conditions must hold (even with neutral density filters).

Enjoy! Lon

londuck wrote in post #2144391
The studio flash unit just is not going to cut it if all this conditions must hold (even with neutral density filters).

The condition that does not need to hold is the shutter speed. With 3 stops of ND filters you could get the shutter speed down to 1/200.

I don't know whether this would be a better solution than reflectors, but it would at least be possible.