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Old Mar 7, 2010, 8:25 PM   #1
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Default How much light do I need?

Thanks to GJToth for pointing me at the DIY page for home studio. That will help me build the soft boxes correctly, but I still need to know how much light I need for 3/4 length portraits. I am planning on two softboxes on either side of the subject, possibly with some back lighting.

If I stick with 100 watt-equivalent compact flourescents I have control over their temperature (my local box store carries 150 and 200 watt-equivalent CFLs but no options for their temperature). How many? I'm thinking of 7 100 watt bulbs in each softbox.

Thanks!

Jim
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Old Mar 8, 2010, 6:08 AM   #2
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I think 3/4 length means something else, after re-reading Kelby. My plan is for taking pictures of standing subjects, perhaps cropping below the knee.
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Old Mar 10, 2010, 8:59 PM   #3
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For good, even portrait lighting, you will likely need the equivalent of 1200w, and probably more if you are using softboxes. This of course, depends on how close you have the lights set up to the subject, as well as how light the room is (paint,ceiling height, etc.) Also note that room color can produce color casts if it isn't fairly neutral.

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Old Mar 17, 2010, 6:24 PM   #4
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That is an excellent point, Brian-

All too often the focus in on how much lighting is required, when in truth, the color of an indoor room also plays a measurable role as well: in terms of color casts and the color modification, that is not always computed into the photo equation.

Sarah Joyce
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Old Mar 21, 2010, 7:24 PM   #5
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VTphotog, you were right on the money. I built a softbox with 1200w equivalent in daylight compact flourescent bulbs and it seems on the fringe of acceptible. I can shoot at 85mm, f5.6, 200 iso, 1/100 sec with the current arrangement. I read that f11 makes for good portraits with an 80mm lens, but I can't imagine what it would take to get enough illumination.

I may try removing the diffuser, or substituting the thin cotton cloth with something else. As you suggested, the diffuser takes away some intensity in return for the diffusion.
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Old Mar 21, 2010, 8:10 PM   #6
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IF you have adult models, you can probably get them to hold still enough to drop your shutter speed a stop or two and use smaller aperture, but f/5.6 should give you enough DOF for portraits, unless you want b/g in focus also. In most cases, sharpness isn't the trait most people look for in portraiture anyway.
Glad the light worked out OK. Once you get comfortable with your setup, you might want to add a few things like hair lights, catch lights, etc.

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Old Mar 22, 2010, 8:44 PM   #7
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I'm curious about various portrait settings, but I suppose I should start a thread in a different location to explore those ideas. I don't need a big DOF, but my Kelby book rather bluntly exclaimed f11 with an 80-100mm lens to be the portrait "sweet spot".

I don't have the headroom for hair lights. I did give a home-made reflector a try and it worked wonderfully. I'm currently exploring ways to illuminate the background. My white backdrop is grey, which I understand to be a result of the amount of lighting it receives. I may also experiment with using my on-board flash, toned down a couple stops, for fill light.

And Sarah, thanks for your input of course. I'm tinkering in my garage for the moment, but will be performing the portrait shots in a greyish room with a white ceiling - all in all not a bad arrangement.

Jim
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