Ok ok if you are doing colour work then this wouldn’ t qualify as a neutral density filter but in this case I my aim is black and white only. The basic goal is to make a filter I can use to try capturing moderately long exposures (5-30 secs) before sunset. I have a cokin filter holder so the aim was to make the DIY filters fit this system as this would allow the filters to be easily attached and detached from the camera.
First of all I brought 2 pieces of welding glass, a grade 8 and a grade 10. Total cost for both pieces of glass $11NZ.
Then my clever wife came up with idea of cutting two strips of sturdy cardboard to fit alongside the welding glass to increase the width to the same size as a standard cokin filter (see photo). The pieces of card were then attached to the long edge of the glass with tape on both sides.
The filters were then attached to the camera to try a few test shots. The results are shown below. The images were captured just after sunset.
Test exposures for the grade 8 welding glass.
Before 1/5 of a second at f13 ISO 200
After 30 seconds at f13 ISO 200
Difference 7 stops (determined using the exposure calculator at http://imaginatorium.org/stuff/stops.htm)
Test exposures for the grade 10 welding glass.
before 1/13 of a second at f22 ISO 400
After 30 seconds at f6.3 ISO 400
Difference 12 stops
A dry run like the tests above certainly provided some interesting results. But in all reality I will need to try these in a more realistic situation and see how useful they would be. If these filters pass this test then the welding glass also comes in grades 12 and 6 so these would be interesting to try. It will be interesting to see how the mounts hold up, these may need improvements.
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This entry was posted on Wednesday, January 19th, 2011 at 9:55 pm
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