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There are lots of DIY IR-pass filters... Stacking colored gels (colored transparency sheets). Stacking ND filters. Crossing polarizing filters. Variable ND filter. Floppy disk – particularly poor because of metal content. Developed color film. Unexposed if reversal (slide film). Exposed if negative. – Undeveloped and B&W films won't work well because ...


Hook up lens from my old glasses for near sight correction solves the problem.


The earliest investigation of the right constant c that I am aware of is Petzval's 1859 On the camera obscura. The paper is predominantly about a new lens design he has created but he begins with an investigation of the optimum radius of a pinhole for resolution of the image. Resolution is defined as the ability to discern the difference of two very close ...

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