fresnel lens from overhead projector

Craig Wactor · 5-Nov-2005, 01:55

Can you use a fresnel from an overhead projector on a large format camera? I know nothing about grove pitch or focal length, why they matter and how a fresnel works. What values are good for use with a wide angle lens?

Michael Gudzinowicz · 5-Nov-2005, 10:49

The focal length of the fresnel lens should be close to that of the wide angle lens.

If you don't know the focal length, project an image of the sun to a sidewalk, and measure the distance from the image to the center of the fresnel lens.

Mike

Dan Fromm · 5-Nov-2005, 12:47

The ones I've seen at Edmund Scientific, now Edumund Industrial Optics but still three miles from my house, were a bit thick. The best use I've found for them was in projected flash rigs. But if you have one, trying is cheap.

5-Nov-2005, 01:55	#1
Craig Wactor Join Date: Jul 2005 Posts: 178	fresnel lens from overhead projector Can you use a fresnel from an overhead projector on a large format camera? I know nothing about grove pitch or focal length, why they matter and how a fresnel works. What values are good for use with a wide angle lens?

5-Nov-2005, 10:49	#2
Michael Gudzinowicz Join Date: Oct 2005 Posts: 142	fresnel lens from overhead projector The focal length of the fresnel lens should be close to that of the wide angle lens. If you don't know the focal length, project an image of the sun to a sidewalk, and measure the distance from the image to the center of the fresnel lens. Mike

5-Nov-2005, 12:47	#3
Dan Fromm Join Date: Dec 2001 Posts: 2,522	fresnel lens from overhead projector The ones I've seen at Edmund Scientific, now Edumund Industrial Optics but still three miles from my house, were a bit thick. The best use I've found for them was in projected flash rigs. But if you have one, trying is cheap.

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