Wednesday, June 8, 2011

Welding Glass as a Neutral Density Filter

After seeing an article on DIY Photography about using welding glass as a neutral density filter, I decided to give it a go. The purpose of an ND filter is to reduce the amount of light that sensor (in this case) receives, with changing the colors. However, the welding glass, which you can get at Amazon [US Forge 104 Shaded #10 Welding Lens], has a deep greenish cast. Shade 10 glass serves as a 14-stop filter, according to others' estimates.

This cast required me to set a custom white balance, by holding a white piece of paper in front of the lens after attaching the filter. Setting the white balance in this manner tells the camera that what is, in reality, this particular shade of green, should be rendered as a white object. Ideally, this will render naturally-colored subjects so long as the filter is in place.

I secured the filter by using 4 rubberbands in much the same manner as on the DIY site. Because the plate of glass will not sit absolutely flush against the lens, light leaks may occur. In order to prevent this, you can drape some sort of cloth (I used a pillow case) over the top of the camera and lens.

There are many instances in which you might want to decrease the amount of light that reaches your camera's sensor, and many of them involve water. In order to test out my setup, I went to Baines Dam in Gardendale. The amount of water running over the dam to the creek below was low, thanks to our month long drought. But there was enough to allow for that milky-misty effect that can sometimes be nice in scenes involving moving water.

While this idea was certainly not original to me, I enjoyed implementing it, as a low-cost solution to a not-uncommon problem. Hopefully, it will yield creative opportunities in the future.

1 comment:

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