DIY find fresnel focal length??
Re: DIY find fresnel focal length??
CardBoardBoxProcessor wrote:
I used my better beamer and it was great. So I want to make my own for my sigma 150-600mm S to make up for its poor appeature of 6.3 at 600mm.
Questions:
do I want the focal length to be adjusted for the bulb itself or the front of the flash?
How do I figure out my fresnel's focal length t?
My theory is that I open a window and perfect the image on a wall. Where ever distant objects are most clear is infinity focus. Is that correct?. Refer to image.
You could also focus the Sun light on the sheet of paper and find the distance between the lens and the paper while the image of the Sun is smallest. But be careful not to burn the house!
Fujifilm FinePix HS10
Sony Cyber-shot DSC-HX90V
Panasonic Lumix DMC-GX7
Panasonic Lumix G Vario 14-140mm F3.5-5.6 O.I.S
Panasonic 20mm F1.7 II
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Apr 6, 2016
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Apr 6, 2016
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Apr 6, 2016
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Apr 9, 2016
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Apr 6, 2016
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Apr 9, 2016
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Apr 3, 2021
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