How to get less DOF with strobes

Started Oct 18, 2013 | Discussions
Tremint Senior Member • Posts: 1,143
How to get less DOF with strobes

Strobes are too powerful to get a lower DOF.

Heard few suggestions to cut light

1) Use ND filter

2) Use modelling light (resulting in using higher ISO)

4) Use flash instead of strobes

Am interested in using strobes so that I can use a lower ISO. And I like the method of using the variable ND filter. Any suggestions would be great.

TH - NikonStrobist
TH - NikonStrobist Regular Member • Posts: 391
Re: How to get less DOF with strobes

Tremint wrote:

Strobes are too powerful to get a lower DOF.

There are lots of ways to cut down the amount of light your strobes are throwing on your subject.
If you can't reduce the power by conventional means, try doubling the distance to the subject, for instance, to let the inverse square law become your ally, or add in (more) diffusers/modifiers which often take at least one f-stop off your equation.

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michaeladawson Forum Pro • Posts: 12,243
Re: How to get less DOF with strobes

Tremint wrote:

Strobes are too powerful to get a lower DOF.

Heard few suggestions to cut light

1) Use ND filter

2) Use modelling light (resulting in using higher ISO)

4) Use flash instead of strobes

Am interested in using strobes so that I can use a lower ISO. And I like the method of using the variable ND filter. Any suggestions would be great.

Do you already have the strobes and you know they're too powerful from actual experience?  Because what you are saying does not have to be true if you buy the right strobes.  For instance, Einstein units go down to 1/128th power (under 5 Ws).  Or get strobes with less power to begin with.  Or as someone else suggested, move your strobes further away.  Although you'll have to get larger diffusers if you want to maintain the same quality of light.

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Mike Dawson

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OP Tremint Senior Member • Posts: 1,143
Re: How to get less DOF with strobes

Yes I have the strobes. I did lower the light and still found that I couldn't open as wide as I wanted to go.  And I dont want to move the light backwards (already have a large softbox) since it will affect the softness of the light.

nikoboivin Regular Member • Posts: 157
Re: How to get less DOF with strobes
1

Tremint wrote:

Yes I have the strobes. I did lower the light and still found that I couldn't open as wide as I wanted to go. And I dont want to move the light backwards (already have a large softbox) since it will affect the softness of the light.

The other way to get less DOF is to use a longer lens and move backwards yourself if you have the space to do so.  For example, if you have a 70-200mm and are using it at 70-100, try moving backwards and going at 200mm and you'll see your DOF getting smaller.

birdpix Senior Member • Posts: 1,411
Re: How to get less DOF with strobes

You can add extra diffusion material in your softbox or on the front of it, like some of the Roscoe Tough Spun, Silk, or Frost. You can stack those diffusers till you get the reduction you want - we used to use 3 or 4 layers of it on hairlight with only barndoors and it worked great.

Roscoe also makes large sheets of ND filters that you can cut, tape, and fashion in to a shape that covers your strobe in case you did not want to add to much ND to your camera lens. Too much ND on your camera can make focusing (and sometimes composing and viewing images) very hard if you are in a dark studio.

We had a bunch of Alien Bee 1600's and found they were too strong in small rooms, so we ended up buying some 800's and that made things a lot simpler - and we got faster flash duration to boot.

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Eric in Florida

PS - there are also some sellers on ebay offering diffusion "socks" that fit right over your flash head to reduce some of the output. Those can work, just never leave your modeling light on for long as they can be fire risks!

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Phil
Phil Veteran Member • Posts: 3,142
Re: How to get less DOF with strobes
1

You can also unsync your flash.

I haven't needed to yet, but Pocket Wizard's TTL system can override sync (I think by responding the flash is in High Speed Sync and then tuning the flash timing) and the cameras are going right up to 1/8000th shutter speed. The light is not perfect, or should I say the curtain timing is not perfect so you wind up cropping an edge or composing the shot so the strobe is not lighting anything along that edge but you get to shoot wide open.

See http://www.pocketwizard.com/products/transmitter_receiver/36/AC9/features/

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Phil Agur
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The Sage Knows Senior Member • Posts: 1,170
Changing focal length & moving back=same DOF
1

nikoboivin wrote:

The other way to get less DOF is to use a longer lens and move backwards yourself if you have the space to do so. For example, if you have a 70-200mm and are using it at 70-100, try moving backwards and going at 200mm and you'll see your DOF getting smaller.

The distant "background"will be blurrier because a smaller view of it will be magnified more but the DOF will be exactly the same. That is, the maximum distance in front of and behind the focus point (presumably where the subject is) before the image appears too blurry to be considered "sharp" will be the same in both cases.

This is clearly explained using geometry (rather than a lot of math) in "Depth of Field and Bokeh" published by Carl Zeiss Camera Lens Division: http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf

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Robert

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