Grids change the shape of light coming from an external flash, making it a small beam instead of a broad expanse of light. I learned about grids on Strobist, of course, and here's how I built mine.
1. Get some black drinking straws.
I got mine at a restaurant supply store, but not before scouring the city looking for a restaurant that has them. Word on the street is I can find them at Panera, but the chain has yet to reach Manhattan. And since I would never advocate grabbing a handful, you should eat at Panera every day for about two months, order a soda each time, then carefully wash out your straw and set it aside.
2. Cut the straws.
I cut mine to 2.25 inches, mainly because could get three pieces out of each straw that way. Longer straws means a more focused light.
3. Cut and fold some cardboard.
Cut out a long strip of cardboard, about 2.75 inches thick. This will wrap around the face of your flash. Make one fold in the cardboard towards the middle. What's more important than fitting snug on the flash is fitting snug to the straws, so lay out a row of straws slightly wider than your flash's head, starting at your fold, and mark where they end. Note how many straws that row is (mine was 13) and fold the cardboard again (making a 'u' shaped piece). Make sure the sides are square to each other.
4. Start laying some straw.
Put some glue on the bottom and sides of each straw and start putting them down like bricks. Once you have an initial row of 13, the next row will sit inside those, having 12 straws, then the third row will have 13. Make sure the end pieces get glued to the sides of the cardboard.
5. End the stacking.
Once your rows have reached the height of your flash, you're ready to close the cardboard ring. If you don't let the glue dry, you'll see you have quite a malleable stack of straws, which makes closing off the ring difficult, but not impossible. Best to let the glue dry, but if you're impatient like me, just proceed carefully and do not squeeze the sides of the grid, as it will cause the rows to buckle. Scoring the cardboard by making a small cut on the outside of the fold will help it fold easily.
6. Tape it off.
After sealing the cardboard top to the straws with glue, use gaffers tape, or duct tape if you're so inclined, to wrap the outside of the grid. Add some velcro to the inside (if you're reading this far, I'm assuming you already have velcro on your flash).
7. Use it or lose it.
I'm going to start in the film noir exercise from Strobist. But you can use it for anything that needs just a little light in exactly the right spot.
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