# Help me calculate how much light I need.



## DaveGBx (Jan 5, 2009)

So here's my situation: the company I work for will be selling sets of classroom furniture. There are four sets. Each set is an entire classroom. The idea is that inside one of our warehouses we will build a "classroom" that is 20'w x 20'l x 8'h to photograph the sets of furniture in. So, what I need to calculate is the amount of lighting I need to adequately light this room. How many watts will be necessary to light this space? There will be no ceiling so lighting will be coming from above and from one maybe two lateral sides. Are there any equations that will tell me how many watts of strobe lighting I will need to light 3,200 cubic feet?

I'm used to product, people and landscape shots. This is a new scenario for me so any help would be greatly appreciated!


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## JerryPH (Jan 5, 2009)

What is your budget, becuase to light a 20 X 20 foot area is going to depend a LOT on this.

Also how much lighting experience do you have?  That will play more than anything else.

How about  four 400W/s lights strategically placed in an angled cross-lit situation on 10-12 foot stands remotely triggered.  Likely 4 X 60" silver bounce umbrellas and... 

Looking at this, it may just be cheaper to hire a pro and get the shots done than buy all this equipment.  Likely turn out better too.


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## DaveGBx (Jan 5, 2009)

Well, our budget probably tops out at 2,500 or so for lighting. We already have five  broncolor CH-4123 500w heads with soft boxes as well as a four novatrons for smaller items. The idea here is that we don't want to drag our lighting back and forth between our primary studio and this "classroom" which will also be used to show case our products to potential buyers. As far as lighting experience goes I have relatively thorough understanding of the dynamics of lighting, just not in this particular scenario where I have to figure out how much power to request. 

So you think that four 400W/s lights will do the trick?

Our original hope for this project was to send it to this place that has rooms with interchangeable walls and a wealth of lighting already in place for furniture market shoots. But the higher-ups have different ideas, so we're just playing it by ear right now.

Thanks for your input!


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## JerryPH (Jan 5, 2009)

Well, do the obvious.  Use the most powerful lights that you have available and dial it down if needed. A larger area like this is going to take lots of room to shoot and very deep DOF.  Aperture settings of F/8 or higher may be needed.  No one knows your needs better than you.

To do this, without seeing it in person is like trying to fix someone's car over the phone or fixing someone's computer over the internet.  There is not much more that can be said except try it out and see if it works for you.  Your experience and understanding of lighting and expectations will dictate whether you get it in 15 minutes or 15 hours... lol

Heck, to even shoot this whole thing, you may be obliged to bring in a cherry picker and get the camera 20-30 feet off the ground to get the top view with a lens that has enough focal length to minimize distortion.


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## tsaraleksi (Jan 5, 2009)

I've lit up a banquet hall with two Alienbee B800 strobes, the trick is to bounce the light. The downside is that you have a ton of light but not much directionality.


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## JerryPH (Jan 5, 2009)

There is no ceiling to bounce light in this case.  Imagine 4 walls with a room setup inside it... and nothing above... hence the comment about a cherry picker going up high to get the shot of the room... but done right, this could be an advantage not a set-back


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## DaveGBx (Jan 5, 2009)

A cherry picker, nice! Your one step ahead of me, the next obstacle is to get high enough (in side a warehouse) to get the shot. We'll probably end up using a forklift or something.

tsaraleksi, thanks for the input. but I think the lack of a ceiling and being enclosed in a warehouse will hinder my ability to bounce much off of existing structures. Though if I could find a good way to bounce the light I could reduce the cost of this shoot.

Unless anyone has any other suggestions I'm going to request four 400W/s heads.


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## JerryPH (Jan 5, 2009)

DaveGBx said:


> Unless anyone has any other suggestions I'm going to request four 400W/s heads.



Did you not mention that you already had 5 X 500 W/s lights already?  What is wrong with using these?


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## DaveGBx (Jan 5, 2009)

We don't want to have to do the back and forth between two buildings with the equipment. Potentially the "classroom" will have it's own lighting. 

I'm just trying to figure out how much it will need to look good. I'm used to lighting standard stuff like people and objects but I've never done a scene where everything in a room needs to be perfectly lit. You know what I mean?


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## JerryPH (Jan 5, 2009)

It's thousands less to do a little back and forth oce or twice than buy lighting and not getting something that works for you.  Also, did you even stop to consider what kind of light modifiers would work for you?  Especially since the 2 buildings are one beside another and it is not likely that you will use the ones in the warehouse very often.

Now, I do not think anyone will argue the fact that single 400 or 500 W/s studio strobes will have much issues lighting an average 5 X 5 foot area, however, at the very least, I would make sure it is enough.  I think it wiser to test things out with what you have now and KNOW, rather than take advice blindly from anyone on the net... myself included. 

Testing out light modifers is also a huge consideration.  You could go from bare bulb to umbrella to a custom made 5 X 10 foot softbox with 2 X 500 W/s lights in it, X 2 to cover the entire unit, raised up 5-10 feet over the "roof" for one HUGE massive diffused area of light.  

There are so many options, its not even funny, but again, I would at least test out things some before investing thousands of dollars.


Knowledge is power.


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## Ls3D (Jan 5, 2009)

Funny thing is I have software that can use photometric data, raytracing & radiosity lighting models to simulate light plots from know (measured) lighting instruments.

Of course one could just finish the job by replacing your products with 3d models and shaders et all.

I have modeled a few continuous light situations using this tool and false color renderings, but it was hard to compare the study to the constructed results.

Interesting problem, especially in light of the deep DOF that was mentioned.

-Shea


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## Flash Harry (Jan 6, 2009)

I'd get as many halogen lights (cheap builder's variety) and permanently light the space to your requirements, yes these are "hot" lights but come cheaply and will do the job. Horses for courses. H


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