|Paul C. Buff, Inc. Technical Forum
|Reflector coverage formula
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|Author:||RNPhotog [ Fri May 19, 2017 3:52 am ]|
|Post subject:||Reflector coverage formula|
Is there a formula for figuring out the coverage of the various reflectors? For example, the 11" reflectors coverage at 65 ft would be...?
|Author:||Technical Support [ Fri May 19, 2017 9:15 am ]|
|Post subject:||Re: Reflector coverage formula|
If you need the actual formula, I can get that for you. If you need a close ball park, you can visit this link: http://www.paulcbuff.com/popups/grids/7_grid_chart.php
This graph shows the beam spread of various grids when installed on a 7" reflector. The 11LTR is 28 degrees, so I would use the 30 degree zone for reference. As the distance doubles, so does the diameter.
Yes, an 11" reflector would have a slightly larger area than the 7", but at 65 feet it is irrelevant (it would be a 4" difference at any distance).
So at 65 feet, you are looking at a 40' spread.
incidentally, at ISO100 and 640Ws, you are looking at f/5.6.
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